Userspace falls short when trying to find out whether a specific memory
range is eligible for THP. There are usecases that would like to know
that
http://lkml.kernel.org/r/alpine.DEB.2.21.1809251248450.50347@chino.kir.corp.google.com
: This is used to identify heap mappings that should be able to fault thp
: but do not, and they normally point to a low-on-memory or fragmentation
: issue.
The only way to deduce this now is to query for hg resp. nh flags and
confronting the state with the global setting. Except that there is also
PR_SET_THP_DISABLE that might change the picture. So the final logic is
not trivial. Moreover the eligibility of the vma depends on the type of
VMA as well. In the past we have supported only anononymous memory VMAs
but things have changed and shmem based vmas are supported as well these
days and the query logic gets even more complicated because the
eligibility depends on the mount option and another global configuration
knob.
Simplify the current state and report the THP eligibility in
/proc/<pid>/smaps for each existing vma. Reuse
transparent_hugepage_enabled for this purpose. The original
implementation of this function assumes that the caller knows that the vma
itself is supported for THP so make the core checks into
__transparent_hugepage_enabled and use it for existing callers.
__show_smap just use the new transparent_hugepage_enabled which also
checks the vma support status (please note that this one has to be out of
line due to include dependency issues).
[mhocko@kernel.org: fix oops with NULL ->f_mapping]
Link: http://lkml.kernel.org/r/20181224185106.GC16738@dhcp22.suse.cz
Link: http://lkml.kernel.org/r/20181211143641.3503-3-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Paul Oppenheimer <bepvte@gmail.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "THP eligibility reporting via proc".
This series of three patches aims at making THP eligibility reporting much
more robust and long term sustainable. The trigger for the change is a
regression report [2] and the long follow up discussion. In short the
specific application didn't have good API to query whether a particular
mapping can be backed by THP so it has used VMA flags to workaround that.
These flags represent a deep internal state of VMAs and as such they
should be used by userspace with a great deal of caution.
A similar has happened for [3] when users complained that VM_MIXEDMAP is
no longer set on DAX mappings. Again a lack of a proper API led to an
abuse.
The first patch in the series tries to emphasise that that the semantic of
flags might change and any application consuming those should be really
careful.
The remaining two patches provide a more suitable interface to address [2]
and provide a consistent API to query the THP status both for each VMA and
process wide as well. [1]
http://lkml.kernel.org/r/20181120103515.25280-1-mhocko@kernel.org [2]
http://lkml.kernel.org/r/http://lkml.kernel.org/r/alpine.DEB.2.21.1809241054050.224429@chino.kir.corp.google.com
[3] http://lkml.kernel.org/r/20181002100531.GC4135@quack2.suse.cz
This patch (of 3):
Even though vma flags exported via /proc/<pid>/smaps are explicitly
documented to be not guaranteed for future compatibility the warning
doesn't go far enough because it doesn't mention semantic changes to those
flags. And they are important as well because these flags are a deep
implementation internal to the MM code and the semantic might change at
any time.
Let's consider two recent examples:
http://lkml.kernel.org/r/20181002100531.GC4135@quack2.suse.cz
: commit e1fb4a0864 "dax: remove VM_MIXEDMAP for fsdax and device dax" has
: removed VM_MIXEDMAP flag from DAX VMAs. Now our testing shows that in the
: mean time certain customer of ours started poking into /proc/<pid>/smaps
: and looks at VMA flags there and if VM_MIXEDMAP is missing among the VMA
: flags, the application just fails to start complaining that DAX support is
: missing in the kernel.
http://lkml.kernel.org/r/alpine.DEB.2.21.1809241054050.224429@chino.kir.corp.google.com
: Commit 1860033237 ("mm: make PR_SET_THP_DISABLE immediately active")
: introduced a regression in that userspace cannot always determine the set
: of vmas where thp is ineligible.
: Userspace relies on the "nh" flag being emitted as part of /proc/pid/smaps
: to determine if a vma is eligible to be backed by hugepages.
: Previous to this commit, prctl(PR_SET_THP_DISABLE, 1) would cause thp to
: be disabled and emit "nh" as a flag for the corresponding vmas as part of
: /proc/pid/smaps. After the commit, thp is disabled by means of an mm
: flag and "nh" is not emitted.
: This causes smaps parsing libraries to assume a vma is eligible for thp
: and ends up puzzling the user on why its memory is not backed by thp.
In both cases userspace was relying on a semantic of a specific VMA flag.
The primary reason why that happened is a lack of a proper interface.
While this has been worked on and it will be fixed properly, it seems that
our wording could see some refinement and be more vocal about semantic
aspect of these flags as well.
Link: http://lkml.kernel.org/r/20181211143641.3503-2-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Paul Oppenheimer <bepvte@gmail.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
offline_pages() is already declared in this file.
Just remove the duplicated one.
Link: http://lkml.kernel.org/r/20181205031357.24769-1-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
To avoid having to change many call sites everytime we want to add a
parameter use a structure to group all parameters for the mmu_notifier
invalidate_range_start/end cakks. No functional changes with this patch.
[akpm@linux-foundation.org: coding style fixes]
Link: http://lkml.kernel.org/r/20181205053628.3210-3-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ross Zwisler <zwisler@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krcmar <rkrcmar@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Felix Kuehling <felix.kuehling@amd.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
From: Jérôme Glisse <jglisse@redhat.com>
Subject: mm/mmu_notifier: use structure for invalidate_range_start/end calls v3
fix build warning in migrate.c when CONFIG_MMU_NOTIFIER=n
Link: http://lkml.kernel.org/r/20181213171330.8489-3-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "mmu notifier contextual informations", v2.
This patchset adds contextual information, why an invalidation is
happening, to mmu notifier callback. This is necessary for user of mmu
notifier that wish to maintains their own data structure without having to
add new fields to struct vm_area_struct (vma).
For instance device can have they own page table that mirror the process
address space. When a vma is unmap (munmap() syscall) the device driver
can free the device page table for the range.
Today we do not have any information on why a mmu notifier call back is
happening and thus device driver have to assume that it is always an
munmap(). This is inefficient at it means that it needs to re-allocate
device page table on next page fault and rebuild the whole device driver
data structure for the range.
Other use case beside munmap() also exist, for instance it is pointless
for device driver to invalidate the device page table when the
invalidation is for the soft dirtyness tracking. Or device driver can
optimize away mprotect() that change the page table permission access for
the range.
This patchset enables all this optimizations for device drivers. I do not
include any of those in this series but another patchset I am posting will
leverage this.
The patchset is pretty simple from a code point of view. The first two
patches consolidate all mmu notifier arguments into a struct so that it is
easier to add/change arguments. The last patch adds the contextual
information (munmap, protection, soft dirty, clear, ...).
This patch (of 3):
To avoid having to change many callback definition everytime we want to
add a parameter use a structure to group all parameters for the
mmu_notifier invalidate_range_start/end callback. No functional changes
with this patch.
[akpm@linux-foundation.org: fix drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c kerneldoc]
Link: http://lkml.kernel.org/r/20181205053628.3210-2-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Jason Gunthorpe <jgg@mellanox.com> [infiniband]
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ross Zwisler <zwisler@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krcmar <rkrcmar@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Christian Koenig <christian.koenig@amd.com>
Cc: Felix Kuehling <felix.kuehling@amd.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We have received a bug report that an injected MCE about faulty memory
prevents memory offline to succeed on 4.4 base kernel. The underlying
reason was that the HWPoison page has an elevated reference count and the
migration keeps failing. There are two problems with that. First of all
it is dubious to migrate the poisoned page because we know that accessing
that memory is possible to fail. Secondly it doesn't make any sense to
migrate a potentially broken content and preserve the memory corruption
over to a new location.
Oscar has found out that 4.4 and the current upstream kernels behave
slightly differently with his simply testcase
===
int main(void)
{
int ret;
int i;
int fd;
char *array = malloc(4096);
char *array_locked = malloc(4096);
fd = open("/tmp/data", O_RDONLY);
read(fd, array, 4095);
for (i = 0; i < 4096; i++)
array_locked[i] = 'd';
ret = mlock((void *)PAGE_ALIGN((unsigned long)array_locked), sizeof(array_locked));
if (ret)
perror("mlock");
sleep (20);
ret = madvise((void *)PAGE_ALIGN((unsigned long)array_locked), 4096, MADV_HWPOISON);
if (ret)
perror("madvise");
for (i = 0; i < 4096; i++)
array_locked[i] = 'd';
return 0;
}
===
+ offline this memory.
In 4.4 kernels he saw the hwpoisoned page to be returned back to the LRU
list
kernel: [<ffffffff81019ac9>] dump_trace+0x59/0x340
kernel: [<ffffffff81019e9a>] show_stack_log_lvl+0xea/0x170
kernel: [<ffffffff8101ac71>] show_stack+0x21/0x40
kernel: [<ffffffff8132bb90>] dump_stack+0x5c/0x7c
kernel: [<ffffffff810815a1>] warn_slowpath_common+0x81/0xb0
kernel: [<ffffffff811a275c>] __pagevec_lru_add_fn+0x14c/0x160
kernel: [<ffffffff811a2eed>] pagevec_lru_move_fn+0xad/0x100
kernel: [<ffffffff811a334c>] __lru_cache_add+0x6c/0xb0
kernel: [<ffffffff81195236>] add_to_page_cache_lru+0x46/0x70
kernel: [<ffffffffa02b4373>] extent_readpages+0xc3/0x1a0 [btrfs]
kernel: [<ffffffff811a16d7>] __do_page_cache_readahead+0x177/0x200
kernel: [<ffffffff811a18c8>] ondemand_readahead+0x168/0x2a0
kernel: [<ffffffff8119673f>] generic_file_read_iter+0x41f/0x660
kernel: [<ffffffff8120e50d>] __vfs_read+0xcd/0x140
kernel: [<ffffffff8120e9ea>] vfs_read+0x7a/0x120
kernel: [<ffffffff8121404b>] kernel_read+0x3b/0x50
kernel: [<ffffffff81215c80>] do_execveat_common.isra.29+0x490/0x6f0
kernel: [<ffffffff81215f08>] do_execve+0x28/0x30
kernel: [<ffffffff81095ddb>] call_usermodehelper_exec_async+0xfb/0x130
kernel: [<ffffffff8161c045>] ret_from_fork+0x55/0x80
And that latter confuses the hotremove path because an LRU page is
attempted to be migrated and that fails due to an elevated reference
count. It is quite possible that the reuse of the HWPoisoned page is some
kind of fixed race condition but I am not really sure about that.
With the upstream kernel the failure is slightly different. The page
doesn't seem to have LRU bit set but isolate_movable_page simply fails and
do_migrate_range simply puts all the isolated pages back to LRU and
therefore no progress is made and scan_movable_pages finds same set of
pages over and over again.
Fix both cases by explicitly checking HWPoisoned pages before we even try
to get reference on the page, try to unmap it if it is still mapped. As
explained by Naoya:
: Hwpoison code never unmapped those for no big reason because
: Ksm pages never dominate memory, so we simply didn't have strong
: motivation to save the pages.
Also put WARN_ON(PageLRU) in case there is a race and we can hit LRU
HWPoison pages which shouldn't happen but I couldn't convince myself about
that. Naoya has noted the following:
: Theoretically no such gurantee, because try_to_unmap() doesn't have a
: guarantee of success and then memory_failure() returns immediately
: when hwpoison_user_mappings fails.
: Or the following code (comes after hwpoison_user_mappings block) also impli=
: es
: that the target page can still have PageLRU flag.
:
: /*
: * Torn down by someone else?
: */
: if (PageLRU(p) && !PageSwapCache(p) && p->mapping =3D=3D NULL) {
: action_result(pfn, MF_MSG_TRUNCATED_LRU, MF_IGNORED);
: res =3D -EBUSY;
: goto out;
: }
:
: So I think it's OK to keep "if (WARN_ON(PageLRU(page)))" block in
: current version of your patch.
Link: http://lkml.kernel.org/r/20181206120135.14079-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Oscar Salvador <osalvador@suse.com>
Debugged-by: Oscar Salvador <osalvador@suse.com>
Tested-by: Oscar Salvador <osalvador@suse.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
kmemleak_scan() goes through all online nodes and tries to scan all used
pages.
We can do better and use pfn_to_online_page(), so in case we have
CONFIG_MEMORY_HOTPLUG, offlined pages will be skiped automatically. For
boxes where CONFIG_MEMORY_HOTPLUG is not present, pfn_to_online_page()
will fallback to pfn_valid().
Another little optimization is to check if the page belongs to the node we
are currently checking, so in case we have nodes interleaved we will not
check the same pfn multiple times.
I ran some tests:
Add some memory to node1 and node2 making it interleaved:
(qemu) object_add memory-backend-ram,id=ram0,size=1G
(qemu) device_add pc-dimm,id=dimm0,memdev=ram0,node=1
(qemu) object_add memory-backend-ram,id=ram1,size=1G
(qemu) device_add pc-dimm,id=dimm1,memdev=ram1,node=2
(qemu) object_add memory-backend-ram,id=ram2,size=1G
(qemu) device_add pc-dimm,id=dimm2,memdev=ram2,node=1
Then, we offline that memory:
# for i in {32..39} ; do echo "offline" > /sys/devices/system/node/node1/memory$i/state;done
# for i in {48..55} ; do echo "offline" > /sys/devices/system/node/node1/memory$i/state;don
# for i in {40..47} ; do echo "offline" > /sys/devices/system/node/node2/memory$i/state;done
And we run kmemleak_scan:
# echo "scan" > /sys/kernel/debug/kmemleak
before the patch:
kmemleak: time spend: 41596 us
after the patch:
kmemleak: time spend: 34899 us
[akpm@linux-foundation.org: remove stray newline, per Oscar]
Link: http://lkml.kernel.org/r/20181206131918.25099-1-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Suggested-by: Michal Hocko <mhocko@suse.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Whilst no architectures actually enable support for huge p4d mappings in
the vmap area, the code that is implemented should be using
break-before-make, as we do for pud and pmd huge entries.
Link: http://lkml.kernel.org/r/1544120495-17438-6-git-send-email-will.deacon@arm.com
Signed-off-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Toshi Kani <toshi.kani@hpe.com>
Cc: Chintan Pandya <cpandya@codeaurora.org>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The current ioremap() code uses a phys_addr variable at each level of page
table, which is confusingly offset by subtracting the base virtual address
being mapped so that adding the current virtual address back on when
iterating through the page table entries gives back the corresponding
physical address.
This is fairly confusing and results in all users of phys_addr having to
add the current virtual address back on. Instead, this patch just updates
phys_addr when iterating over the page table entries, ensuring that it's
always up-to-date and doesn't require explicit offsetting.
Link: http://lkml.kernel.org/r/1544120495-17438-5-git-send-email-will.deacon@arm.com
Signed-off-by: Will Deacon <will.deacon@arm.com>
Tested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Chintan Pandya <cpandya@codeaurora.org>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The core code already has a check for pXd_none(), so remove it from the
architecture implementation.
Link: http://lkml.kernel.org/r/1544120495-17438-4-git-send-email-will.deacon@arm.com
Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Toshi Kani <toshi.kani@hpe.com>
Cc: Chintan Pandya <cpandya@codeaurora.org>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The core code already has a check for pXd_none(), so remove it from the
architecture implementation.
Link: http://lkml.kernel.org/r/1544120495-17438-3-git-send-email-will.deacon@arm.com
Signed-off-by: Will Deacon <will.deacon@arm.com>
Cc: Chintan Pandya <cpandya@codeaurora.org>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The recently merged API for ensuring break-before-make on page-table
entries when installing huge mappings in the vmalloc/ioremap region is
fairly counter-intuitive, resulting in the arch freeing functions (e.g.
pmd_free_pte_page()) being called even on entries that aren't present.
This resulted in a minor bug in the arm64 implementation, giving rise to
spurious VM_WARN messages.
This patch moves the pXd_present() checks out into the core code,
refactoring the callsites at the same time so that we avoid the complex
conjunctions when determining whether or not we can put down a huge
mapping.
Link: http://lkml.kernel.org/r/1544120495-17438-2-git-send-email-will.deacon@arm.com
Signed-off-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Toshi Kani <toshi.kani@hpe.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Chintan Pandya <cpandya@codeaurora.org>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
page always is not NULL, so we may remove this useless check.
Link: http://lkml.kernel.org/r/154419752044.18559.2452963074922917720.stgit@localhost.localdomain
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: Cyrill Gorcunov <gorcunov@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Certain pages that are never mapped to userspace have a type indicated in
the page_type field of their struct pages (e.g. PG_buddy). page_type
overlaps with _mapcount so set the count to 0 and avoid calling
page_mapcount() for these pages.
[anthony.yznaga@oracle.com: incorporate feedback from Matthew Wilcox]
Link: http://lkml.kernel.org/r/1544481313-27318-1-git-send-email-anthony.yznaga@oracle.com
Link: http://lkml.kernel.org/r/1543963526-27917-1-git-send-email-anthony.yznaga@oracle.com
Signed-off-by: Anthony Yznaga <anthony.yznaga@oracle.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Miles Chen <miles.chen@mediatek.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Because kpagecount_read() fakes success if map counts are not being
collected, clamp the page count passed to it by walk_pfn() to the pages
value returned by the preceding call to kpageflags_read().
Link: http://lkml.kernel.org/r/1543962269-26116-1-git-send-email-anthony.yznaga@oracle.com
Fixes: 7f1d23e607 ("tools/vm/page-types.c: include shared map counts")
Signed-off-by: Anthony Yznaga <anthony.yznaga@oracle.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since commit 03e85f9d5f ("mm/page_alloc: Introduce
free_area_init_core_hotplug"), some functions changed to only be called
during system initialization. Concretly, free_area_init_node() and the
functions that hang from it.
Also, some variables are no longer used after the system has gone
through initialization. So this could be considered as a late clean-up
for that patch.
This patch changes the functions from __meminit to __init, and the
variables from __meminitdata to __initdata.
In return, we get some KBs back:
Before:
Freeing unused kernel image memory: 2472K
After:
Freeing unused kernel image memory: 2480K
Link: http://lkml.kernel.org/r/20181204111507.4808-1-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Pavel Tatashin <pavel.tatashin@microsoft.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
write_cache_pages() is used in both background and integrity writeback
scenarios by various filesystems. Background writeback is mostly
concerned with cleaning a certain number of dirty pages based on various
mm heuristics. It may not write the full set of dirty pages or wait for
I/O to complete. Integrity writeback is responsible for persisting a set
of dirty pages before the writeback job completes. For example, an
fsync() call must perform integrity writeback to ensure data is on disk
before the call returns.
write_cache_pages() unconditionally breaks out of its processing loop in
the event of a ->writepage() error. This is fine for background
writeback, which had no strict requirements and will eventually come
around again. This can cause problems for integrity writeback on
filesystems that might need to clean up state associated with failed page
writeouts. For example, XFS performs internal delayed allocation
accounting before returning a ->writepage() error, where applicable. If
the current writeback happens to be associated with an unmount and
write_cache_pages() completes the writeback prematurely due to error, the
filesystem is unmounted in an inconsistent state if dirty+delalloc pages
still exist.
To handle this problem, update write_cache_pages() to always process the
full set of pages for integrity writeback regardless of ->writepage()
errors. Save the first encountered error and return it to the caller once
complete. This facilitates XFS (or any other fs that expects integrity
writeback to process the entire set of dirty pages) to clean up its
internal state completely in the event of persistent mapping errors.
Background writeback continues to exit on the first error encountered.
[akpm@linux-foundation.org: fix typo in comment]
Link: http://lkml.kernel.org/r/20181116134304.32440-1-bfoster@redhat.com
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Function show_mem() is used to print system memory status when user
requires or fail to allocate memory. Generally, this is a best effort
information so any races with memory hotplug (or very theoretically an
early initialization) should be tolerable and the worst that could happen
is to print an imprecise node state.
Drop the resize lock because this is the only place which might hold the
lock from the interrupt context and so all other callers might use a
simple spinlock. Even though this doesn't solve any real issue it makes
the code easier to follow and tiny more effective.
Link: http://lkml.kernel.org/r/20181129235532.9328-1-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fixes gcc '-Wunused-but-set-variable' warning:
mm/hmm.c: In function 'hmm_devmem_ref_kill':
mm/hmm.c:995:21: warning:
variable 'devmem' set but not used [-Wunused-but-set-variable]
It not used any more since 35d39f953d4e ("mm, hmm: replace
hmm_devmem_pages_create() with devm_memremap_pages()")
Link: http://lkml.kernel.org/r/1543629971-128377-1-git-send-email-yuehaibing@huawei.com
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Reviewed-by: Jérôme Glisse <jglisse@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
During online_pages phase, pgdat->nr_zones will be updated in case this
zone is empty.
Currently the online_pages phase is protected by the global locks
(device_device_hotplug_lock and mem_hotplug_lock), which ensures there is
no contention during the update of nr_zones.
These global locks introduces scalability issues (especially the second
one), which slow down code relying on get_online_mems(). This is also a
preparation for not having to rely on get_online_mems() but instead some
more fine grained locks.
The patch moves init_currently_empty_zone under both zone_span_writelock
and pgdat_resize_lock because both the pgdat state is changed (nr_zones)
and the zone's start_pfn. Also this patch changes the documentation of
node_size_lock to include the protection of nr_zones.
Link: http://lkml.kernel.org/r/20181203205016.14123-1-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since the information needed in sparse_add_one_section() is node id to
allocate proper memory, it is not necessary to pass its pgdat.
This patch changes the prototype of sparse_add_one_section() to pass node
id directly. This is intended to reduce misleading that
sparse_add_one_section() would touch pgdat.
Link: http://lkml.kernel.org/r/20181204085657.20472-2-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
pgdat_resize_lock is used to protect pgdat's memory region information
like: node_start_pfn, node_present_pages, etc. While in function
sparse_add/remove_one_section(), pgdat_resize_lock is used to protect
initialization/release of one mem_section. This looks not proper.
These code paths are currently protected by mem_hotplug_lock currently but
should there ever be any reason for locking at the sparse layer a
dedicated lock should be introduced.
Following is the current call trace of sparse_add/remove_one_section()
mem_hotplug_begin()
arch_add_memory()
add_pages()
__add_pages()
__add_section()
sparse_add_one_section()
mem_hotplug_done()
mem_hotplug_begin()
arch_remove_memory()
__remove_pages()
__remove_section()
sparse_remove_one_section()
mem_hotplug_done()
The comment above the pgdat_resize_lock also mentions "Holding this will
also guarantee that any pfn_valid() stays that way.", which is true with
the current implementation and false after this patch. But current
implementation doesn't meet this comment. There isn't any pfn walkers to
take the lock so this looks like a relict from the past. This patch also
removes this comment.
[richard.weiyang@gmail.com: v4]
Link: http://lkml.kernel.org/r/20181204085657.20472-1-richard.weiyang@gmail.com
[mhocko@suse.com: changelog suggestion]
Link: http://lkml.kernel.org/r/20181128091243.19249-1-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pagetable page doesn't touch page->mapping or have any used field that
overlaps with it. No need to clear mapping in dtor. In fact, doing so
might mask problems that otherwise would be detected by bad_page().
Link: http://lkml.kernel.org/r/20181128235525.58780-1-yuzhao@google.com
Signed-off-by: Yu Zhao <yuzhao@google.com>
Reviewed-by: Matthew Wilcox <willy@infradead.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Keith Busch <keith.busch@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If there are lots of write IO with flash device, it could have a
wearout problem of storage. To overcome the problem, admin needs
to design write limitation to guarantee flash health
for entire product life.
This patch creates a new knob "writeback_limit" for zram.
writeback_limit's default value is 0 so that it doesn't limit
any writeback. If admin want to measure writeback count in a
certain period, he could know it via /sys/block/zram0/bd_stat's
3rd column.
If admin want to limit writeback as per-day 400M, he could do it
like below.
MB_SHIFT=20
4K_SHIFT=12
echo $((400<<MB_SHIFT>>4K_SHIFT)) > \
/sys/block/zram0/writeback_limit.
If admin want to allow further write again, he could do it like below
echo 0 > /sys/block/zram0/writeback_limit
If admin want to see remaining writeback budget,
cat /sys/block/zram0/writeback_limit
The writeback_limit count will reset whenever you reset zram (e.g., system
reboot, echo 1 > /sys/block/zramX/reset) so keeping how many of writeback
happened until you reset the zram to allocate extra writeback budget in
next setting is user's job.
[minchan@kernel.org: v4]
Link: http://lkml.kernel.org/r/20181203024045.153534-8-minchan@kernel.org
Link: http://lkml.kernel.org/r/20181127055429.251614-8-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Joey Pabalinas <joeypabalinas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
bd_stat represents things that happened in the backing device. Currently
it supports bd_counts, bd_reads and bd_writes which are helpful to
understand wearout of flash and memory saving.
[minchan@kernel.org: v4]
Link: http://lkml.kernel.org/r/20181203024045.153534-7-minchan@kernel.org
Link: http://lkml.kernel.org/r/20181127055429.251614-7-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Joey Pabalinas <joeypabalinas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add a new feature "zram idle/huge page writeback". In the zram-swap use
case, zram usually has many idle/huge swap pages. It's pointless to keep
them in memory (ie, zram).
To solve this problem, this feature introduces idle/huge page writeback to
the backing device so the goal is to save more memory space on embedded
systems.
Normal sequence to use idle/huge page writeback feature is as follows,
while (1) {
# mark allocated zram slot to idle
echo all > /sys/block/zram0/idle
# leave system working for several hours
# Unless there is no access for some blocks on zram,
# they are still IDLE marked pages.
echo "idle" > /sys/block/zram0/writeback
or/and
echo "huge" > /sys/block/zram0/writeback
# write the IDLE or/and huge marked slot into backing device
# and free the memory.
}
Per the discussion at
https://lore.kernel.org/lkml/20181122065926.GG3441@jagdpanzerIV/T/#u,
This patch removes direct incommpressibe page writeback feature
(d2afd25114f4 ("zram: write incompressible pages to backing device")).
Below concerns from Sergey:
== &< ==
"IDLE writeback" is superior to "incompressible writeback".
"incompressible writeback" is completely unpredictable and uncontrollable;
it depens on data patterns and compression algorithms. While "IDLE
writeback" is predictable.
I even suspect, that, *ideally*, we can remove "incompressible writeback".
"IDLE pages" is a super set which also includes "incompressible" pages.
So, technically, we still can do "incompressible writeback" from "IDLE
writeback" path; but a much more reasonable one, based on a page idling
period.
I understand that you want to keep "direct incompressible writeback"
around. ZRAM is especially popular on devices which do suffer from flash
wearout, so I can see "incompressible writeback" path becoming a dead
code, long term.
== &< ==
Below concerns from Minchan:
== &< ==
My concern is if we enable CONFIG_ZRAM_WRITEBACK in this implementation,
both hugepage/idlepage writeck will turn on. However someuser want to
enable only idlepage writeback so we need to introduce turn on/off knob
for hugepage or new CONFIG_ZRAM_IDLEPAGE_WRITEBACK for those usecase. I
don't want to make it complicated *if possible*.
Long term, I imagine we need to make VM aware of new swap hierarchy a
little bit different with as-is. For example, first high priority swap
can return -EIO or -ENOCOMP, swap try to fallback to next lower priority
swap device. With that, hugepage writeback will work tranparently.
So we could regard it as regression because incompressible pages doesn't
go to backing storage automatically. Instead, user should do it via "echo
huge" > /sys/block/zram/writeback" manually.
== &< ==
Link: http://lkml.kernel.org/r/20181127055429.251614-6-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Joey Pabalinas <joeypabalinas@gmail.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
To support idle page writeback with upcoming patches, this patch
introduces a new ZRAM_IDLE flag.
Userspace can mark zram slots as "idle" via
"echo all > /sys/block/zramX/idle"
which marks every allocated zram slot as ZRAM_IDLE.
User could see it by /sys/kernel/debug/zram/zram0/block_state.
300 75.033841 ...i
301 63.806904 s..i
302 63.806919 ..hi
Once there is IO for the slot, the mark will be disappeared.
300 75.033841 ...
301 63.806904 s..i
302 63.806919 ..hi
Therefore, 300th block is idle zpage. With this feature,
user can how many zram has idle pages which are waste of memory.
Link: http://lkml.kernel.org/r/20181127055429.251614-5-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Joey Pabalinas <joeypabalinas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Rename some variables and restructure some code for better readability in
writeback and zs_free_page.
Link: http://lkml.kernel.org/r/20181127055429.251614-4-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Joey Pabalinas <joeypabalinas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "zram idle page writeback", v3.
Inherently, swap device has many idle pages which are rare touched since
it was allocated. It is never problem if we use storage device as swap.
However, it's just waste for zram-swap.
This patchset supports zram idle page writeback feature.
* Admin can define what is idle page "no access since X time ago"
* Admin can define when zram should writeback them
* Admin can define when zram should stop writeback to prevent wearout
Details are in each patch's description.
This patch (of 7):
================================
WARNING: inconsistent lock state
4.19.0+ #390 Not tainted
--------------------------------
inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
zram_verify/2095 [HC0[0]:SC1[1]:HE1:SE0] takes:
00000000b1828693 (&(&zram->bitmap_lock)->rlock){+.?.}, at: put_entry_bdev+0x1e/0x50
{SOFTIRQ-ON-W} state was registered at:
_raw_spin_lock+0x2c/0x40
zram_make_request+0x755/0xdc9
generic_make_request+0x373/0x6a0
submit_bio+0x6c/0x140
__swap_writepage+0x3a8/0x480
shrink_page_list+0x1102/0x1a60
shrink_inactive_list+0x21b/0x3f0
shrink_node_memcg.constprop.99+0x4f8/0x7e0
shrink_node+0x7d/0x2f0
do_try_to_free_pages+0xe0/0x300
try_to_free_pages+0x116/0x2b0
__alloc_pages_slowpath+0x3f4/0xf80
__alloc_pages_nodemask+0x2a2/0x2f0
__handle_mm_fault+0x42e/0xb50
handle_mm_fault+0x55/0xb0
__do_page_fault+0x235/0x4b0
page_fault+0x1e/0x30
irq event stamp: 228412
hardirqs last enabled at (228412): [<ffffffff98245846>] __slab_free+0x3e6/0x600
hardirqs last disabled at (228411): [<ffffffff98245625>] __slab_free+0x1c5/0x600
softirqs last enabled at (228396): [<ffffffff98e0031e>] __do_softirq+0x31e/0x427
softirqs last disabled at (228403): [<ffffffff98072051>] irq_exit+0xd1/0xe0
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&(&zram->bitmap_lock)->rlock);
<Interrupt>
lock(&(&zram->bitmap_lock)->rlock);
*** DEADLOCK ***
no locks held by zram_verify/2095.
stack backtrace:
CPU: 5 PID: 2095 Comm: zram_verify Not tainted 4.19.0+ #390
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
Call Trace:
<IRQ>
dump_stack+0x67/0x9b
print_usage_bug+0x1bd/0x1d3
mark_lock+0x4aa/0x540
__lock_acquire+0x51d/0x1300
lock_acquire+0x90/0x180
_raw_spin_lock+0x2c/0x40
put_entry_bdev+0x1e/0x50
zram_free_page+0xf6/0x110
zram_slot_free_notify+0x42/0xa0
end_swap_bio_read+0x5b/0x170
blk_update_request+0x8f/0x340
scsi_end_request+0x2c/0x1e0
scsi_io_completion+0x98/0x650
blk_done_softirq+0x9e/0xd0
__do_softirq+0xcc/0x427
irq_exit+0xd1/0xe0
do_IRQ+0x93/0x120
common_interrupt+0xf/0xf
</IRQ>
With writeback feature, zram_slot_free_notify could be called in softirq
context by end_swap_bio_read. However, bitmap_lock is not aware of that
so lockdep yell out:
get_entry_bdev
spin_lock(bitmap->lock);
irq
softirq
end_swap_bio_read
zram_slot_free_notify
zram_slot_lock <-- deadlock prone
zram_free_page
put_entry_bdev
spin_lock(bitmap->lock); <-- deadlock prone
With akpm's suggestion (i.e. bitmap operation is already atomic), we
could remove bitmap lock. It might fail to find a empty slot if serious
contention happens. However, it's not severe problem because huge page
writeback has already possiblity to fail if there is severe memory
pressure. Worst case is just keeping the incompressible in memory, not
storage.
The other problem is zram_slot_lock in zram_slot_slot_free_notify. To
make it safe is this patch introduces zram_slot_trylock where
zram_slot_free_notify uses it. Although it's rare to be contented, this
patch adds new debug stat "miss_free" to keep monitoring how often it
happens.
Link: http://lkml.kernel.org/r/20181127055429.251614-2-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Joey Pabalinas <joeypabalinas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Kmemleak does not play well with KASAN (tested on both HPE Apollo 70 and
Huawei TaiShan 2280 aarch64 servers).
After calling start_kernel()->setup_arch()->kasan_init(), kmemleak early
log buffer went from something like 280 to 260000 which caused kmemleak
disabled and crash dump memory reservation failed. The multitude of
kmemleak_alloc() calls is from nested loops while KASAN is setting up full
memory mappings, so let early kmemleak allocations skip those
memblock_alloc_internal() calls came from kasan_init() given that those
early KASAN memory mappings should not reference to other memory. Hence,
no kmemleak false positives.
kasan_init
kasan_map_populate [1]
kasan_pgd_populate [2]
kasan_pud_populate [3]
kasan_pmd_populate [4]
kasan_pte_populate [5]
kasan_alloc_zeroed_page
memblock_alloc_try_nid
memblock_alloc_internal
kmemleak_alloc
[1] for_each_memblock(memory, reg)
[2] while (pgdp++, addr = next, addr != end)
[3] while (pudp++, addr = next, addr != end && pud_none(READ_ONCE(*pudp)))
[4] while (pmdp++, addr = next, addr != end && pmd_none(READ_ONCE(*pmdp)))
[5] while (ptep++, addr = next, addr != end && pte_none(READ_ONCE(*ptep)))
Link: http://lkml.kernel.org/r/1543442925-17794-1-git-send-email-cai@gmx.us
Signed-off-by: Qian Cai <cai@gmx.us>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is a preparation for the next patch.
Currently, we only call release_mem_region_adjustable() in __remove_pages
if the zone is not ZONE_DEVICE, because resources that belong to HMM/devm
are being released by themselves with devm_release_mem_region.
Since we do not want to touch any zone/page stuff during the removing of
the memory (but during the offlining), we do not want to check for the
zone here. So we need another way to tell release_mem_region_adjustable()
to not realease the resource in case it belongs to HMM/devm.
HMM/devm acquires/releases a resource through
devm_request_mem_region/devm_release_mem_region.
These resources have the flag IORESOURCE_MEM, while resources acquired by
hot-add memory path (register_memory_resource()) contain
IORESOURCE_SYSTEM_RAM.
So, we can check for this flag in release_mem_region_adjustable, and if
the resource does not contain such flag, we know that we are dealing with
a HMM/devm resource, so we can back off.
Link: http://lkml.kernel.org/r/20181127162005.15833-3-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "Do not touch pages in hot-remove path", v2.
This patchset aims for two things:
1) A better definition about offline and hot-remove stage
2) Solving bugs where we can access non-initialized pages
during hot-remove operations [2] [3].
This is achieved by moving all page/zone handling to the offline
stage, so we do not need to access pages when hot-removing memory.
[1] https://patchwork.kernel.org/cover/10691415/
[2] https://patchwork.kernel.org/patch/10547445/
[3] https://www.spinics.net/lists/linux-mm/msg161316.html
This patch (of 5):
This is a preparation for the following-up patches. The idea of passing
the nid is that it will allow us to get rid of the zone parameter
afterwards.
Link: http://lkml.kernel.org/r/20181127162005.15833-2-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When DEFERRED_STRUCT_PAGE_INIT is configured, only the first section of
each node's highest zone is initialized before defer stage.
static_init_pgcnt is used to store the number of pages like this:
pgdat->static_init_pgcnt = min_t(unsigned long, PAGES_PER_SECTION,
pgdat->node_spanned_pages);
because we don't want to overflow zone's range.
But this is not necessary, since defer_init() is called like this:
memmap_init_zone()
for pfn in [start_pfn, end_pfn)
defer_init(pfn, end_pfn)
In case (pgdat->node_spanned_pages < PAGES_PER_SECTION), the loop would
stop before calling defer_init().
BTW, comparing PAGES_PER_SECTION with node_spanned_pages is not correct,
since nr_initialised is zone based instead of node based. Even
node_spanned_pages is bigger than PAGES_PER_SECTION, its highest zone
would have pages less than PAGES_PER_SECTION.
Link: http://lkml.kernel.org/r/20181122094807.6985-1-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Waiting on a page migration entry has used wait_on_page_locked() all along
since 2006: but you cannot safely wait_on_page_locked() without holding a
reference to the page, and that extra reference is enough to make
migrate_page_move_mapping() fail with -EAGAIN, when a racing task faults
on the entry before migrate_page_move_mapping() gets there.
And that failure is retried nine times, amplifying the pain when trying to
migrate a popular page. With a single persistent faulter, migration
sometimes succeeds; with two or three concurrent faulters, success becomes
much less likely (and the more the page was mapped, the worse the overhead
of unmapping and remapping it on each try).
This is especially a problem for memory offlining, where the outer level
retries forever (or until terminated from userspace), because a heavy
refault workload can trigger an endless loop of migration failures.
wait_on_page_locked() is the wrong tool for the job.
David Herrmann (but was he the first?) noticed this issue in 2014:
https://marc.info/?l=linux-mm&m=140110465608116&w=2
Tim Chen started a thread in August 2017 which appears relevant:
https://marc.info/?l=linux-mm&m=150275941014915&w=2 where Kan Liang went
on to implicate __migration_entry_wait():
https://marc.info/?l=linux-mm&m=150300268411980&w=2 and the thread ended
up with the v4.14 commits: 2554db9165 ("sched/wait: Break up long wake
list walk") 11a19c7b09 ("sched/wait: Introduce wakeup boomark in
wake_up_page_bit")
Baoquan He reported "Memory hotplug softlock issue" 14 November 2018:
https://marc.info/?l=linux-mm&m=154217936431300&w=2
We have all assumed that it is essential to hold a page reference while
waiting on a page lock: partly to guarantee that there is still a struct
page when MEMORY_HOTREMOVE is configured, but also to protect against
reuse of the struct page going to someone who then holds the page locked
indefinitely, when the waiter can reasonably expect timely unlocking.
But in fact, so long as wait_on_page_bit_common() does the put_page(), and
is careful not to rely on struct page contents thereafter, there is no
need to hold a reference to the page while waiting on it. That does mean
that this case cannot go back through the loop: but that's fine for the
page migration case, and even if used more widely, is limited by the "Stop
walking if it's locked" optimization in wake_page_function().
Add interface put_and_wait_on_page_locked() to do this, using "behavior"
enum in place of "lock" arg to wait_on_page_bit_common() to implement it.
No interruptible or killable variant needed yet, but they might follow: I
have a vague notion that reporting -EINTR should take precedence over
return from wait_on_page_bit_common() without knowing the page state, so
arrange it accordingly - but that may be nothing but pedantic.
__migration_entry_wait() still has to take a brief reference to the page,
prior to calling put_and_wait_on_page_locked(): but now that it is dropped
before waiting, the chance of impeding page migration is very much
reduced. Should we perhaps disable preemption across this?
shrink_page_list()'s __ClearPageLocked(): that was a surprise! This
survived a lot of testing before that showed up. PageWaiters may have
been set by wait_on_page_bit_common(), and the reference dropped, just
before shrink_page_list() succeeds in freezing its last page reference: in
such a case, unlock_page() must be used. Follow the suggestion from
Michal Hocko, just revert a978d6f521 ("mm: unlockless reclaim") now:
that optimization predates PageWaiters, and won't buy much these days; but
we can reinstate it for the !PageWaiters case if anyone notices.
It does raise the question: should vmscan.c's is_page_cache_freeable() and
__remove_mapping() now treat a PageWaiters page as if an extra reference
were held? Perhaps, but I don't think it matters much, since
shrink_page_list() already had to win its trylock_page(), so waiters are
not very common there: I noticed no difference when trying the bigger
change, and it's surely not needed while put_and_wait_on_page_locked() is
only used for page migration.
[willy@infradead.org: add put_and_wait_on_page_locked() kerneldoc]
Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1811261121330.1116@eggly.anvils
Signed-off-by: Hugh Dickins <hughd@google.com>
Reported-by: Baoquan He <bhe@redhat.com>
Tested-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Nick Piggin <npiggin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The current oom report doesn't display victim's memcg context during the
global OOM situation. While this information is not strictly needed, it
can be really helpful for containerized environments to locate which
container has lost a process. Now that we have a single line for the oom
context, we can trivially add both the oom memcg (this can be either
global_oom or a specific memcg which hits its hard limits) and task_memcg
which is the victim's memcg.
Below is the single line output in the oom report after this patch.
- global oom context information:
oom-kill:constraint=<constraint>,nodemask=<nodemask>,cpuset=<cpuset>,mems_allowed=<mems_allowed>,global_oom,task_memcg=<memcg>,task=<comm>,pid=<pid>,uid=<uid>
- memcg oom context information:
oom-kill:constraint=<constraint>,nodemask=<nodemask>,cpuset=<cpuset>,mems_allowed=<mems_allowed>,oom_memcg=<memcg>,task_memcg=<memcg>,task=<comm>,pid=<pid>,uid=<uid>
[penguin-kernel@I-love.SAKURA.ne.jp: use pr_cont() in mem_cgroup_print_oom_context()]
Link: http://lkml.kernel.org/r/201812190723.wBJ7NdkN032628@www262.sakura.ne.jp
Link: http://lkml.kernel.org/r/1542799799-36184-2-git-send-email-ufo19890607@gmail.com
Signed-off-by: yuzhoujian <yuzhoujian@didichuxing.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: David Rientjes <rientjes@google.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Roman Gushchin <guro@fb.com>
Cc: Yang Shi <yang.s@alibaba-inc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
and propagate through down the call stack.
Link: http://lkml.kernel.org/r/20181124091411.GC10969@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Those strings are immutable in fact.
Link: http://lkml.kernel.org/r/20181124090327.GA10877@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
An external fragmentation event was previously described as
When the page allocator fragments memory, it records the event using
the mm_page_alloc_extfrag event. If the fallback_order is smaller
than a pageblock order (order-9 on 64-bit x86) then it's considered
an event that will cause external fragmentation issues in the future.
The kernel reduces the probability of such events by increasing the
watermark sizes by calling set_recommended_min_free_kbytes early in the
lifetime of the system. This works reasonably well in general but if
there are enough sparsely populated pageblocks then the problem can still
occur as enough memory is free overall and kswapd stays asleep.
This patch introduces a watermark_boost_factor sysctl that allows a zone
watermark to be temporarily boosted when an external fragmentation causing
events occurs. The boosting will stall allocations that would decrease
free memory below the boosted low watermark and kswapd is woken if the
calling context allows to reclaim an amount of memory relative to the size
of the high watermark and the watermark_boost_factor until the boost is
cleared. When kswapd finishes, it wakes kcompactd at the pageblock order
to clean some of the pageblocks that may have been affected by the
fragmentation event. kswapd avoids any writeback, slab shrinkage and swap
from reclaim context during this operation to avoid excessive system
disruption in the name of fragmentation avoidance. Care is taken so that
kswapd will do normal reclaim work if the system is really low on memory.
This was evaluated using the same workloads as "mm, page_alloc: Spread
allocations across zones before introducing fragmentation".
1-socket Skylake machine
config-global-dhp__workload_thpfioscale XFS (no special madvise)
4 fio threads, 1 THP allocating thread
--------------------------------------
4.20-rc3 extfrag events < order 9: 804694
4.20-rc3+patch: 408912 (49% reduction)
4.20-rc3+patch1-4: 18421 (98% reduction)
4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Amean fault-base-1 653.58 ( 0.00%) 652.71 ( 0.13%)
Amean fault-huge-1 0.00 ( 0.00%) 178.93 * -99.00%*
4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Percentage huge-1 0.00 ( 0.00%) 5.12 ( 100.00%)
Note that external fragmentation causing events are massively reduced by
this path whether in comparison to the previous kernel or the vanilla
kernel. The fault latency for huge pages appears to be increased but that
is only because THP allocations were successful with the patch applied.
1-socket Skylake machine
global-dhp__workload_thpfioscale-madvhugepage-xfs (MADV_HUGEPAGE)
-----------------------------------------------------------------
4.20-rc3 extfrag events < order 9: 291392
4.20-rc3+patch: 191187 (34% reduction)
4.20-rc3+patch1-4: 13464 (95% reduction)
thpfioscale Fault Latencies
4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Min fault-base-1 912.00 ( 0.00%) 905.00 ( 0.77%)
Min fault-huge-1 127.00 ( 0.00%) 135.00 ( -6.30%)
Amean fault-base-1 1467.55 ( 0.00%) 1481.67 ( -0.96%)
Amean fault-huge-1 1127.11 ( 0.00%) 1063.88 * 5.61%*
4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Percentage huge-1 77.64 ( 0.00%) 83.46 ( 7.49%)
As before, massive reduction in external fragmentation events, some jitter
on latencies and an increase in THP allocation success rates.
2-socket Haswell machine
config-global-dhp__workload_thpfioscale XFS (no special madvise)
4 fio threads, 5 THP allocating threads
----------------------------------------------------------------
4.20-rc3 extfrag events < order 9: 215698
4.20-rc3+patch: 200210 (7% reduction)
4.20-rc3+patch1-4: 14263 (93% reduction)
4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Amean fault-base-5 1346.45 ( 0.00%) 1306.87 ( 2.94%)
Amean fault-huge-5 3418.60 ( 0.00%) 1348.94 ( 60.54%)
4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Percentage huge-5 0.78 ( 0.00%) 7.91 ( 910.64%)
There is a 93% reduction in fragmentation causing events, there is a big
reduction in the huge page fault latency and allocation success rate is
higher.
2-socket Haswell machine
global-dhp__workload_thpfioscale-madvhugepage-xfs (MADV_HUGEPAGE)
-----------------------------------------------------------------
4.20-rc3 extfrag events < order 9: 166352
4.20-rc3+patch: 147463 (11% reduction)
4.20-rc3+patch1-4: 11095 (93% reduction)
thpfioscale Fault Latencies
4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Amean fault-base-5 6217.43 ( 0.00%) 7419.67 * -19.34%*
Amean fault-huge-5 3163.33 ( 0.00%) 3263.80 ( -3.18%)
4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Percentage huge-5 95.14 ( 0.00%) 87.98 ( -7.53%)
There is a large reduction in fragmentation events with some jitter around
the latencies and success rates. As before, the high THP allocation
success rate does mean the system is under a lot of pressure. However, as
the fragmentation events are reduced, it would be expected that the
long-term allocation success rate would be higher.
Link: http://lkml.kernel.org/r/20181123114528.28802-5-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is a preparation patch that copies the GFP flag __GFP_KSWAPD_RECLAIM
into alloc_flags. This is a preparation patch only that avoids having to
pass gfp_mask through a long callchain in a future patch.
Note that the setting in the fast path happens in alloc_flags_nofragment()
and it may be claimed that this has nothing to do with ALLOC_NO_FRAGMENT.
That's true in this patch but is not true later so it's done now for
easier review to show where the flag needs to be recorded.
No functional change.
[mgorman@techsingularity.net: ALLOC_KSWAPD flag needs to be applied in the !CONFIG_ZONE_DMA32 case]
Link: http://lkml.kernel.org/r/20181126143503.GO23260@techsingularity.net
Link: http://lkml.kernel.org/r/20181123114528.28802-4-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is a preparation patch only, no functional change.
Link: http://lkml.kernel.org/r/20181123114528.28802-3-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "Fragmentation avoidance improvements", v5.
It has been noted before that fragmentation avoidance (aka
anti-fragmentation) is not perfect. Given sufficient time or an adverse
workload, memory gets fragmented and the long-term success of high-order
allocations degrades. This series defines an adverse workload, a definition
of external fragmentation events (including serious) ones and a series
that reduces the level of those fragmentation events.
The details of the workload and the consequences are described in more
detail in the changelogs. However, from patch 1, this is a high-level
summary of the adverse workload. The exact details are found in the
mmtests implementation.
The broad details of the workload are as follows;
1. Create an XFS filesystem (not specified in the configuration but done
as part of the testing for this patch)
2. Start 4 fio threads that write a number of 64K files inefficiently.
Inefficiently means that files are created on first access and not
created in advance (fio parameterr create_on_open=1) and fallocate
is not used (fallocate=none). With multiple IO issuers this creates
a mix of slab and page cache allocations over time. The total size
of the files is 150% physical memory so that the slabs and page cache
pages get mixed
3. Warm up a number of fio read-only threads accessing the same files
created in step 2. This part runs for the same length of time it
took to create the files. It'll fault back in old data and further
interleave slab and page cache allocations. As it's now low on
memory due to step 2, fragmentation occurs as pageblocks get
stolen.
4. While step 3 is still running, start a process that tries to allocate
75% of memory as huge pages with a number of threads. The number of
threads is based on a (NR_CPUS_SOCKET - NR_FIO_THREADS)/4 to avoid THP
threads contending with fio, any other threads or forcing cross-NUMA
scheduling. Note that the test has not been used on a machine with less
than 8 cores. The benchmark records whether huge pages were allocated
and what the fault latency was in microseconds
5. Measure the number of events potentially causing external fragmentation,
the fault latency and the huge page allocation success rate.
6. Cleanup
Overall the series reduces external fragmentation causing events by over 94%
on 1 and 2 socket machines, which in turn impacts high-order allocation
success rates over the long term. There are differences in latencies and
high-order allocation success rates. Latencies are a mixed bag as they
are vulnerable to exact system state and whether allocations succeeded
so they are treated as a secondary metric.
Patch 1 uses lower zones if they are populated and have free memory
instead of fragmenting a higher zone. It's special cased to
handle a Normal->DMA32 fallback with the reasons explained
in the changelog.
Patch 2-4 boosts watermarks temporarily when an external fragmentation
event occurs. kswapd wakes to reclaim a small amount of old memory
and then wakes kcompactd on completion to recover the system
slightly. This introduces some overhead in the slowpath. The level
of boosting can be tuned or disabled depending on the tolerance
for fragmentation vs allocation latency.
Patch 5 stalls some movable allocation requests to let kswapd from patch 4
make some progress. The duration of the stalls is very low but it
is possible to tune the system to avoid fragmentation events if
larger stalls can be tolerated.
The bulk of the improvement in fragmentation avoidance is from patches
1-4 but patch 5 can deal with a rare corner case and provides the option
of tuning a system for THP allocation success rates in exchange for
some stalls to control fragmentation.
This patch (of 5):
The page allocator zone lists are iterated based on the watermarks of each
zone which does not take anti-fragmentation into account. On x86, node 0
may have multiple zones while other nodes have one zone. A consequence is
that tasks running on node 0 may fragment ZONE_NORMAL even though
ZONE_DMA32 has plenty of free memory. This patch special cases the
allocator fast path such that it'll try an allocation from a lower local
zone before fragmenting a higher zone. In this case, stealing of
pageblocks or orders larger than a pageblock are still allowed in the fast
path as they are uninteresting from a fragmentation point of view.
This was evaluated using a benchmark designed to fragment memory before
attempting THP allocations. It's implemented in mmtests as the following
configurations
configs/config-global-dhp__workload_thpfioscale
configs/config-global-dhp__workload_thpfioscale-defrag
configs/config-global-dhp__workload_thpfioscale-madvhugepage
e.g. from mmtests
./run-mmtests.sh --run-monitor --config configs/config-global-dhp__workload_thpfioscale test-run-1
The broad details of the workload are as follows;
1. Create an XFS filesystem (not specified in the configuration but done
as part of the testing for this patch).
2. Start 4 fio threads that write a number of 64K files inefficiently.
Inefficiently means that files are created on first access and not
created in advance (fio parameter create_on_open=1) and fallocate
is not used (fallocate=none). With multiple IO issuers this creates
a mix of slab and page cache allocations over time. The total size
of the files is 150% physical memory so that the slabs and page cache
pages get mixed.
3. Warm up a number of fio read-only processes accessing the same files
created in step 2. This part runs for the same length of time it
took to create the files. It'll refault old data and further
interleave slab and page cache allocations. As it's now low on
memory due to step 2, fragmentation occurs as pageblocks get
stolen.
4. While step 3 is still running, start a process that tries to allocate
75% of memory as huge pages with a number of threads. The number of
threads is based on a (NR_CPUS_SOCKET - NR_FIO_THREADS)/4 to avoid THP
threads contending with fio, any other threads or forcing cross-NUMA
scheduling. Note that the test has not been used on a machine with less
than 8 cores. The benchmark records whether huge pages were allocated
and what the fault latency was in microseconds.
5. Measure the number of events potentially causing external fragmentation,
the fault latency and the huge page allocation success rate.
6. Cleanup the test files.
Note that due to the use of IO and page cache that this benchmark is not
suitable for running on large machines where the time to fragment memory
may be excessive. Also note that while this is one mix that generates
fragmentation that it's not the only mix that generates fragmentation.
Differences in workload that are more slab-intensive or whether SLUB is
used with high-order pages may yield different results.
When the page allocator fragments memory, it records the event using the
mm_page_alloc_extfrag ftrace event. If the fallback_order is smaller than
a pageblock order (order-9 on 64-bit x86) then it's considered to be an
"external fragmentation event" that may cause issues in the future.
Hence, the primary metric here is the number of external fragmentation
events that occur with order < 9. The secondary metric is allocation
latency and huge page allocation success rates but note that differences
in latencies and what the success rate also can affect the number of
external fragmentation event which is why it's a secondary metric.
1-socket Skylake machine
config-global-dhp__workload_thpfioscale XFS (no special madvise)
4 fio threads, 1 THP allocating thread
--------------------------------------
4.20-rc3 extfrag events < order 9: 804694
4.20-rc3+patch: 408912 (49% reduction)
thpfioscale Fault Latencies
4.20.0-rc3 4.20.0-rc3
vanilla lowzone-v5r8
Amean fault-base-1 662.92 ( 0.00%) 653.58 * 1.41%*
Amean fault-huge-1 0.00 ( 0.00%) 0.00 ( 0.00%)
4.20.0-rc3 4.20.0-rc3
vanilla lowzone-v5r8
Percentage huge-1 0.00 ( 0.00%) 0.00 ( 0.00%)
Fault latencies are slightly reduced while allocation success rates remain
at zero as this configuration does not make any special effort to allocate
THP and fio is heavily active at the time and either filling memory or
keeping pages resident. However, a 49% reduction of serious fragmentation
events reduces the changes of external fragmentation being a problem in
the future.
Vlastimil asked during review for a breakdown of the allocation types
that are falling back.
vanilla
3816 MIGRATE_UNMOVABLE
800845 MIGRATE_MOVABLE
33 MIGRATE_UNRECLAIMABLE
patch
735 MIGRATE_UNMOVABLE
408135 MIGRATE_MOVABLE
42 MIGRATE_UNRECLAIMABLE
The majority of the fallbacks are due to movable allocations and this is
consistent for the workload throughout the series so will not be presented
again as the primary source of fallbacks are movable allocations.
Movable fallbacks are sometimes considered "ok" to fallback because they
can be migrated. The problem is that they can fill an
unmovable/reclaimable pageblock causing those allocations to fallback
later and polluting pageblocks with pages that cannot move. If there is a
movable fallback, it is pretty much guaranteed to affect an
unmovable/reclaimable pageblock and while it might not be enough to
actually cause a unmovable/reclaimable fallback in the future, we cannot
know that in advance so the patch takes the only option available to it.
Hence, it's important to control them. This point is also consistent
throughout the series and will not be repeated.
1-socket Skylake machine
global-dhp__workload_thpfioscale-madvhugepage-xfs (MADV_HUGEPAGE)
-----------------------------------------------------------------
4.20-rc3 extfrag events < order 9: 291392
4.20-rc3+patch: 191187 (34% reduction)
thpfioscale Fault Latencies
4.20.0-rc3 4.20.0-rc3
vanilla lowzone-v5r8
Amean fault-base-1 1495.14 ( 0.00%) 1467.55 ( 1.85%)
Amean fault-huge-1 1098.48 ( 0.00%) 1127.11 ( -2.61%)
thpfioscale Percentage Faults Huge
4.20.0-rc3 4.20.0-rc3
vanilla lowzone-v5r8
Percentage huge-1 78.57 ( 0.00%) 77.64 ( -1.18%)
Fragmentation events were reduced quite a bit although this is known
to be a little variable. The latencies and allocation success rates
are similar but they were already quite high.
2-socket Haswell machine
config-global-dhp__workload_thpfioscale XFS (no special madvise)
4 fio threads, 5 THP allocating threads
----------------------------------------------------------------
4.20-rc3 extfrag events < order 9: 215698
4.20-rc3+patch: 200210 (7% reduction)
thpfioscale Fault Latencies
4.20.0-rc3 4.20.0-rc3
vanilla lowzone-v5r8
Amean fault-base-5 1350.05 ( 0.00%) 1346.45 ( 0.27%)
Amean fault-huge-5 4181.01 ( 0.00%) 3418.60 ( 18.24%)
4.20.0-rc3 4.20.0-rc3
vanilla lowzone-v5r8
Percentage huge-5 1.15 ( 0.00%) 0.78 ( -31.88%)
The reduction of external fragmentation events is slight and this is
partially due to the removal of __GFP_THISNODE in commit ac5b2c1891
("mm: thp: relax __GFP_THISNODE for MADV_HUGEPAGE mappings") as THP
allocations can now spill over to remote nodes instead of fragmenting
local memory.
2-socket Haswell machine
global-dhp__workload_thpfioscale-madvhugepage-xfs (MADV_HUGEPAGE)
-----------------------------------------------------------------
4.20-rc3 extfrag events < order 9: 166352
4.20-rc3+patch: 147463 (11% reduction)
thpfioscale Fault Latencies
4.20.0-rc3 4.20.0-rc3
vanilla lowzone-v5r8
Amean fault-base-5 6138.97 ( 0.00%) 6217.43 ( -1.28%)
Amean fault-huge-5 2294.28 ( 0.00%) 3163.33 * -37.88%*
thpfioscale Percentage Faults Huge
4.20.0-rc3 4.20.0-rc3
vanilla lowzone-v5r8
Percentage huge-5 96.82 ( 0.00%) 95.14 ( -1.74%)
There was a slight reduction in external fragmentation events although the
latencies were higher. The allocation success rate is high enough that
the system is struggling and there is quite a lot of parallel reclaim and
compaction activity. There is also a certain degree of luck on whether
processes start on node 0 or not for this patch but the relevance is
reduced later in the series.
Overall, the patch reduces the number of external fragmentation causing
events so the success of THP over long periods of time would be improved
for this adverse workload.
Link: http://lkml.kernel.org/r/20181123114528.28802-2-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Userspace should always be in charge of how to online memory and if memory
should be onlined automatically in the kernel. Let's drop the parameter
to overwrite this - XEN passes memhp_auto_online, just like add_memory(),
so we can directly use that instead internally.
Link: http://lkml.kernel.org/r/20181123123740.27652-1-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Juergen Gross <jgross@suse.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Arun KS <arunks@codeaurora.org>
Cc: Mathieu Malaterre <malat@debian.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In cb5e39b803 ("drivers: base: refactor add_memory_section() to
add_memory_block()"), add_memory_block() is introduced, which is only
invoked in memory_dev_init().
When combining these two loops in memory_dev_init() and
add_memory_block(), they looks like this:
for (i = 0; i < NR_MEM_SECTIONS; i += sections_per_block)
for (j = i;
(j < i + sections_per_block) && j < NR_MEM_SECTIONS;
j++)
Since it is sure the (i < NR_MEM_SECTIONS) and j sits in its own memory
block, the check of (j < NR_MEM_SECTIONS) is not necessary.
This patch just removes this check.
Link: http://lkml.kernel.org/r/20181123222811.18216-1-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Seth Jennings <sjenning@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
__memblock_free_early() is only used by the convenience wrappers, so
essentially we wrap a call to memblock_free() twice. Replace calls of
__memblock_free_early() with calls to memblock_free() and drop the former.
Link: http://lkml.kernel.org/r/20181125102940.GE28634@rapoport-lnx
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Wentao Wang <witallwang@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There are multiple places of freeing a page, they all do the same things
so a common function can be used to reduce code duplicate.
It also avoids bug fixed in one function but left in another.
Link: http://lkml.kernel.org/r/20181119134834.17765-3-aaron.lu@intel.com
Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Pankaj gupta <pagupta@redhat.com>
Cc: Pawel Staszewski <pstaszewski@itcare.pl>
Cc: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
page_frag_free() calls __free_pages_ok() to free the page back to Buddy.
This is OK for high order page, but for order-0 pages, it misses the
optimization opportunity of using Per-Cpu-Pages and can cause zone lock
contention when called frequently.
Pawel Staszewski recently shared his result of 'how Linux kernel handles
normal traffic'[1] and from perf data, Jesper Dangaard Brouer found the
lock contention comes from page allocator:
mlx5e_poll_tx_cq
|
--16.34%--napi_consume_skb
|
|--12.65%--__free_pages_ok
| |
| --11.86%--free_one_page
| |
| |--10.10%--queued_spin_lock_slowpath
| |
| --0.65%--_raw_spin_lock
|
|--1.55%--page_frag_free
|
--1.44%--skb_release_data
Jesper explained how it happened: mlx5 driver RX-page recycle mechanism is
not effective in this workload and pages have to go through the page
allocator. The lock contention happens during mlx5 DMA TX completion
cycle. And the page allocator cannot keep up at these speeds.[2]
I thought that __free_pages_ok() are mostly freeing high order pages and
thought this is an lock contention for high order pages but Jesper
explained in detail that __free_pages_ok() here are actually freeing
order-0 pages because mlx5 is using order-0 pages to satisfy its page pool
allocation request.[3]
The free path as pointed out by Jesper is:
skb_free_head()
-> skb_free_frag()
-> page_frag_free()
And the pages being freed on this path are order-0 pages.
Fix this by doing similar things as in __page_frag_cache_drain() - send
the being freed page to PCP if it's an order-0 page, or directly to Buddy
if it is a high order page.
With this change, Paweł hasn't noticed lock contention yet in his
workload and Jesper has noticed a 7% performance improvement using a micro
benchmark and lock contention is gone. Ilias' test on a 'low' speed 1Gbit
interface on an cortex-a53 shows ~11% performance boost testing with
64byte packets and __free_pages_ok() disappeared from perf top.
[1]: https://www.spinics.net/lists/netdev/msg531362.html
[2]: https://www.spinics.net/lists/netdev/msg531421.html
[3]: https://www.spinics.net/lists/netdev/msg531556.html
[akpm@linux-foundation.org: add comment]
Link: http://lkml.kernel.org/r/20181120014544.GB10657@intel.com
Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Reported-by: Pawel Staszewski <pstaszewski@itcare.pl>
Analysed-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Tested-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Acked-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Acked-by: Tariq Toukan <tariqt@mellanox.com>
Acked-by: Pankaj gupta <pagupta@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Michal Hocko