When we have holes in a normal memory zone, we could endup having
cached_migrate_pfns which may not necessarily be valid, under heavy memory
pressure with swapping enabled ( via __reset_isolation_suitable(),
triggered by kswapd).
Later if we fail to find a page via fast_isolate_freepages(), we may end
up using the migrate_pfn we started the search with, as valid page. This
could lead to accessing NULL pointer derefernces like below, due to an
invalid mem_section pointer.
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008 [47/1825]
Mem abort info:
ESR = 0x96000004
Exception class = DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
Data abort info:
ISV = 0, ISS = 0x00000004
CM = 0, WnR = 0
user pgtable: 4k pages, 48-bit VAs, pgdp = 0000000082f94ae9
[0000000000000008] pgd=0000000000000000
Internal error: Oops: 96000004 [#1] SMP
...
CPU: 10 PID: 6080 Comm: qemu-system-aar Not tainted 510-rc1+ #6
Hardware name: AmpereComputing(R) OSPREY EV-883832-X3-0001/OSPREY, BIOS 4819 09/25/2018
pstate: 60000005 (nZCv daif -PAN -UAO)
pc : set_pfnblock_flags_mask+0x58/0xe8
lr : compaction_alloc+0x300/0x950
[...]
Process qemu-system-aar (pid: 6080, stack limit = 0x0000000095070da5)
Call trace:
set_pfnblock_flags_mask+0x58/0xe8
compaction_alloc+0x300/0x950
migrate_pages+0x1a4/0xbb0
compact_zone+0x750/0xde8
compact_zone_order+0xd8/0x118
try_to_compact_pages+0xb4/0x290
__alloc_pages_direct_compact+0x84/0x1e0
__alloc_pages_nodemask+0x5e0/0xe18
alloc_pages_vma+0x1cc/0x210
do_huge_pmd_anonymous_page+0x108/0x7c8
__handle_mm_fault+0xdd4/0x1190
handle_mm_fault+0x114/0x1c0
__get_user_pages+0x198/0x3c0
get_user_pages_unlocked+0xb4/0x1d8
__gfn_to_pfn_memslot+0x12c/0x3b8
gfn_to_pfn_prot+0x4c/0x60
kvm_handle_guest_abort+0x4b0/0xcd8
handle_exit+0x140/0x1b8
kvm_arch_vcpu_ioctl_run+0x260/0x768
kvm_vcpu_ioctl+0x490/0x898
do_vfs_ioctl+0xc4/0x898
ksys_ioctl+0x8c/0xa0
__arm64_sys_ioctl+0x28/0x38
el0_svc_common+0x74/0x118
el0_svc_handler+0x38/0x78
el0_svc+0x8/0xc
Code: f8607840 f100001f 8b011401 9a801020 (f9400400)
---[ end trace af6a35219325a9b6 ]---
The issue was reported on an arm64 server with 128GB with holes in the
zone (e.g, [32GB@4GB, 96GB@544GB]), with a swap device enabled, while
running 100 KVM guest instances.
This patch fixes the issue by ensuring that the page belongs to a valid
PFN when we fallback to using the lower limit of the scan range upon
failure in fast_isolate_freepages().
Link: http://lkml.kernel.org/r/1558711908-15688-1-git-send-email-suzuki.poulose@arm.com
Fixes: 5a811889de ("mm, compaction: use free lists to quickly locate a migration target")
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reported-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Mel Gorman <mgorman@techsingularity.net>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
syzbot reported the following error from a tree with a head commit of
baf76f0c58 ("slip: make slhc_free() silently accept an error pointer")
BUG: unable to handle kernel paging request at ffffea0003348000
#PF error: [normal kernel read fault]
PGD 12c3f9067 P4D 12c3f9067 PUD 12c3f8067 PMD 0
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 28916 Comm: syz-executor.2 Not tainted 5.1.0-rc6+ #89
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:constant_test_bit arch/x86/include/asm/bitops.h:314 [inline]
RIP: 0010:PageCompound include/linux/page-flags.h:186 [inline]
RIP: 0010:isolate_freepages_block+0x1c0/0xd40 mm/compaction.c:579
Code: 01 d8 ff 4d 85 ed 0f 84 ef 07 00 00 e8 29 00 d8 ff 4c 89 e0 83 85 38 ff
ff ff 01 48 c1 e8 03 42 80 3c 38 00 0f 85 31 0a 00 00 <4d> 8b 2c 24 31 ff 49
c1 ed 10 41 83 e5 01 44 89 ee e8 3a 01 d8 ff
RSP: 0018:ffff88802b31eab8 EFLAGS: 00010246
RAX: 1ffffd4000669000 RBX: 00000000000cd200 RCX: ffffc9000a235000
RDX: 000000000001ca5e RSI: ffffffff81988cc7 RDI: 0000000000000001
RBP: ffff88802b31ebd8 R08: ffff88805af700c0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffea0003348000
R13: 0000000000000000 R14: ffff88802b31f030 R15: dffffc0000000000
FS: 00007f61648dc700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffea0003348000 CR3: 0000000037c64000 CR4: 00000000001426e0
Call Trace:
fast_isolate_around mm/compaction.c:1243 [inline]
fast_isolate_freepages mm/compaction.c:1418 [inline]
isolate_freepages mm/compaction.c:1438 [inline]
compaction_alloc+0x1aee/0x22e0 mm/compaction.c:1550
There is no reproducer and it is difficult to hit -- 1 crash every few
days. The issue is very similar to the fix in commit 6b0868c820
("mm/compaction.c: correct zone boundary handling when resetting pageblock
skip hints"). When isolating free pages around a target pageblock, the
boundary handling is off by one and can stray into the next pageblock.
Triggering the syzbot error requires that the end of pageblock is section
or zone aligned, and that the next section is unpopulated.
A more subtle consequence of the bug is that pageblocks were being
improperly used as migration targets which potentially hurts fragmentation
avoidance in the long-term one page at a time.
A debugging patch revealed that it's definitely possible to stray outside
of a pageblock which is not intended. While syzbot cannot be used to
verify this patch, it was confirmed that the debugging warning no longer
triggers with this patch applied. It has also been confirmed that the THP
allocation stress tests are not degraded by this patch.
Link: http://lkml.kernel.org/r/20190510182124.GI18914@techsingularity.net
Fixes: e332f741a8 ("mm, compaction: be selective about what pageblocks to clear skip hints")
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reported-by: syzbot+d84c80f9fe26a0f7a734@syzkaller.appspotmail.com
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org> # v5.1+
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In preparation for runtime randomization of the zone lists, take all
(well, most of) the list_*() functions in the buddy allocator and put
them in helper functions. Provide a common control point for injecting
additional behavior when freeing pages.
[dan.j.williams@intel.com: fix buddy list helpers]
Link: http://lkml.kernel.org/r/155033679702.1773410.13041474192173212653.stgit@dwillia2-desk3.amr.corp.intel.com
[vbabka@suse.cz: remove del_page_from_free_area() migratetype parameter]
Link: http://lkml.kernel.org/r/4672701b-6775-6efd-0797-b6242591419e@suse.cz
Link: http://lkml.kernel.org/r/154899812264.3165233.5219320056406926223.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Robert Elliott <elliott@hpe.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In a low-memory situation, cc->fast_search_fail can keep increasing as it
is unable to find an available page to isolate in
fast_isolate_freepages(). As the result, it could trigger an error below,
so just compare with the maximum bits can be shifted first.
UBSAN: Undefined behaviour in mm/compaction.c:1160:30
shift exponent 64 is too large for 64-bit type 'unsigned long'
CPU: 131 PID: 1308 Comm: kcompactd1 Kdump: loaded Tainted: G
W L 5.0.0+ #17
Call trace:
dump_backtrace+0x0/0x450
show_stack+0x20/0x2c
dump_stack+0xc8/0x14c
__ubsan_handle_shift_out_of_bounds+0x7e8/0x8c4
compaction_alloc+0x2344/0x2484
unmap_and_move+0xdc/0x1dbc
migrate_pages+0x274/0x1310
compact_zone+0x26ec/0x43bc
kcompactd+0x15b8/0x1a24
kthread+0x374/0x390
ret_from_fork+0x10/0x18
[akpm@linux-foundation.org: code cleanup]
Link: http://lkml.kernel.org/r/20190320203338.53367-1-cai@lca.pw
Fixes: 70b44595ea ("mm, compaction: use free lists to quickly locate a migration source")
Signed-off-by: Qian Cai <cai@lca.pw>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Mikhail Gavrilo reported the following bug being triggered in a Fedora
kernel based on 5.1-rc1 but it is relevant to a vanilla kernel.
kernel: page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
kernel: ------------[ cut here ]------------
kernel: kernel BUG at include/linux/mm.h:1021!
kernel: invalid opcode: 0000 [#1] SMP NOPTI
kernel: CPU: 6 PID: 116 Comm: kswapd0 Tainted: G C 5.1.0-0.rc1.git1.3.fc31.x86_64 #1
kernel: Hardware name: System manufacturer System Product Name/ROG STRIX X470-I GAMING, BIOS 1201 12/07/2018
kernel: RIP: 0010:__reset_isolation_pfn+0x244/0x2b0
kernel: Code: fe 06 e8 0f 8e fc ff 44 0f b6 4c 24 04 48 85 c0 0f 85 dc fe ff ff e9 68 fe ff ff 48 c7 c6 58 b7 2e 8c 4c 89 ff e8 0c 75 00 00 <0f> 0b 48 c7 c6 58 b7 2e 8c e8 fe 74 00 00 0f 0b 48 89 fa 41 b8 01
kernel: RSP: 0018:ffff9e2d03f0fde8 EFLAGS: 00010246
kernel: RAX: 0000000000000034 RBX: 000000000081f380 RCX: ffff8cffbddd6c20
kernel: RDX: 0000000000000000 RSI: 0000000000000006 RDI: ffff8cffbddd6c20
kernel: RBP: 0000000000000001 R08: 0000009898b94613 R09: 0000000000000000
kernel: R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000100000
kernel: R13: 0000000000100000 R14: 0000000000000001 R15: ffffca7de07ce000
kernel: FS: 0000000000000000(0000) GS:ffff8cffbdc00000(0000) knlGS:0000000000000000
kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
kernel: CR2: 00007fc1670e9000 CR3: 00000007f5276000 CR4: 00000000003406e0
kernel: Call Trace:
kernel: __reset_isolation_suitable+0x62/0x120
kernel: reset_isolation_suitable+0x3b/0x40
kernel: kswapd+0x147/0x540
kernel: ? finish_wait+0x90/0x90
kernel: kthread+0x108/0x140
kernel: ? balance_pgdat+0x560/0x560
kernel: ? kthread_park+0x90/0x90
kernel: ret_from_fork+0x27/0x50
He bisected it down to e332f741a8 ("mm, compaction: be selective about
what pageblocks to clear skip hints"). The problem is that the patch in
question was sloppy with respect to the handling of zone boundaries. In
some instances, it was possible for PFNs outside of a zone to be examined
and if those were not properly initialised or poisoned then it would
trigger the VM_BUG_ON. This patch corrects the zone boundary issues when
resetting pageblock skip hints and Mikhail reported that the bug did not
trigger after 30 hours of testing.
Link: http://lkml.kernel.org/r/20190327085424.GL3189@techsingularity.net
Fixes: e332f741a8 ("mm, compaction: be selective about what pageblocks to clear skip hints")
Reported-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
too_many_isolated() in mm/compaction.c looks only at node state, so it
makes more sense to change argument to pgdat instead of zone.
Link: http://lkml.kernel.org/r/20190228083329.31892-3-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Rik van Riel <riel@surriel.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: William Kucharski <william.kucharski@oracle.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 common pattern to access lru_lock from a page pointer:
zone_lru_lock(page_zone(page))
Which is silly, because it unfolds to this:
&NODE_DATA(page_to_nid(page))->node_zones[page_zonenum(page)]->zone_pgdat->lru_lock
while we can simply do
&NODE_DATA(page_to_nid(page))->lru_lock
Remove zone_lru_lock() function, since it's only complicate things. Use
'page_pgdat(page)->lru_lock' pattern instead.
[aryabinin@virtuozzo.com: a slightly better version of __split_huge_page()]
Link: http://lkml.kernel.org/r/20190301121651.7741-1-aryabinin@virtuozzo.com
Link: http://lkml.kernel.org/r/20190228083329.31892-2-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: William Kucharski <william.kucharski@oracle.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>
Compaction is inherently race-prone as a suitable page freed during
compaction can be allocated by any parallel task. This patch uses a
capture_control structure to isolate a page immediately when it is freed
by a direct compactor in the slow path of the page allocator. The
intent is to avoid redundant scanning.
5.0.0-rc1 5.0.0-rc1
selective-v3r17 capture-v3r19
Amean fault-both-1 0.00 ( 0.00%) 0.00 * 0.00%*
Amean fault-both-3 2582.11 ( 0.00%) 2563.68 ( 0.71%)
Amean fault-both-5 4500.26 ( 0.00%) 4233.52 ( 5.93%)
Amean fault-both-7 5819.53 ( 0.00%) 6333.65 ( -8.83%)
Amean fault-both-12 9321.18 ( 0.00%) 9759.38 ( -4.70%)
Amean fault-both-18 9782.76 ( 0.00%) 10338.76 ( -5.68%)
Amean fault-both-24 15272.81 ( 0.00%) 13379.55 * 12.40%*
Amean fault-both-30 15121.34 ( 0.00%) 16158.25 ( -6.86%)
Amean fault-both-32 18466.67 ( 0.00%) 18971.21 ( -2.73%)
Latency is only moderately affected but the devil is in the details. A
closer examination indicates that base page fault latency is reduced but
latency of huge pages is increased as it takes creater care to succeed.
Part of the "problem" is that allocation success rates are close to 100%
even when under pressure and compaction gets harder
5.0.0-rc1 5.0.0-rc1
selective-v3r17 capture-v3r19
Percentage huge-3 96.70 ( 0.00%) 98.23 ( 1.58%)
Percentage huge-5 96.99 ( 0.00%) 95.30 ( -1.75%)
Percentage huge-7 94.19 ( 0.00%) 97.24 ( 3.24%)
Percentage huge-12 94.95 ( 0.00%) 97.35 ( 2.53%)
Percentage huge-18 96.74 ( 0.00%) 97.30 ( 0.58%)
Percentage huge-24 97.07 ( 0.00%) 97.55 ( 0.50%)
Percentage huge-30 95.69 ( 0.00%) 98.50 ( 2.95%)
Percentage huge-32 96.70 ( 0.00%) 99.27 ( 2.65%)
And scan rates are reduced as expected by 6% for the migration scanner
and 29% for the free scanner indicating that there is less redundant
work.
Compaction migrate scanned 20815362 19573286
Compaction free scanned 16352612 11510663
[mgorman@techsingularity.net: remove redundant check]
Link: http://lkml.kernel.org/r/20190201143853.GH9565@techsingularity.net
Link: http://lkml.kernel.org/r/20190118175136.31341-23-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: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pageblock hints are cleared when compaction restarts or kswapd makes
enough progress that it can sleep but it's over-eager in that the bit is
cleared for migration sources with no LRU pages and migration targets
with no free pages. As pageblock skip hint flushes are relatively rare
and out-of-band with respect to kswapd, this patch makes a few more
expensive checks to see if it's appropriate to even clear the bit.
Every pageblock that is not cleared will avoid 512 pages being scanned
unnecessarily on x86-64.
The impact is variable with different workloads showing small
differences in latency, success rates and scan rates. This is expected
as clearing the hints is not that common but doing a small amount of
work out-of-band to avoid a large amount of work in-band later is
generally a good thing.
Link: http://lkml.kernel.org/r/20190118175136.31341-22-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Qian Cai <cai@lca.pw>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
[cai@lca.pw: no stuck in __reset_isolation_pfn()]
Link: http://lkml.kernel.org/r/20190206034732.75687-1-cai@lca.pw
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Once fast searching finishes, there is a possibility that the linear
scanner is scanning full blocks found by the fast scanner earlier. This
patch uses an adaptive stride to sample pageblocks for free pages. The
more consecutive full pageblocks encountered, the larger the stride
until a pageblock with free pages is found. The scanners might meet
slightly sooner but it is an acceptable risk given that the search of
the free lists may still encounter the pages and adjust the cached PFN
of the free scanner accordingly.
5.0.0-rc1 5.0.0-rc1
roundrobin-v3r17 samplefree-v3r17
Amean fault-both-1 0.00 ( 0.00%) 0.00 * 0.00%*
Amean fault-both-3 2752.37 ( 0.00%) 2729.95 ( 0.81%)
Amean fault-both-5 4341.69 ( 0.00%) 4397.80 ( -1.29%)
Amean fault-both-7 6308.75 ( 0.00%) 6097.61 ( 3.35%)
Amean fault-both-12 10241.81 ( 0.00%) 9407.15 ( 8.15%)
Amean fault-both-18 13736.09 ( 0.00%) 10857.63 * 20.96%*
Amean fault-both-24 16853.95 ( 0.00%) 13323.24 * 20.95%*
Amean fault-both-30 15862.61 ( 0.00%) 17345.44 ( -9.35%)
Amean fault-both-32 18450.85 ( 0.00%) 16892.00 ( 8.45%)
The latency is mildly improved offseting some overhead from earlier
patches that are prerequisites for the rest of the series. However, a
major impact is on the free scan rate with an 82% reduction.
5.0.0-rc1 5.0.0-rc1
roundrobin-v3r17 samplefree-v3r17
Compaction migrate scanned 21607271 20116887
Compaction free scanned 95336406 16668703
It's also the first time in the series where the number of pages scanned
by the migration scanner is greater than the free scanner due to the
increased search efficiency.
Link: http://lkml.kernel.org/r/20190118175136.31341-21-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: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
As compaction proceeds and creates high-order blocks, the free list
search gets less efficient as the larger blocks are used as compaction
targets. Eventually, the larger blocks will be behind the migration
scanner for partially migrated pageblocks and the search fails. This
patch round-robins what orders are searched so that larger blocks can be
ignored and find smaller blocks that can be used as migration targets.
The overall impact was small on 1-socket but it avoids corner cases
where the migration/free scanners meet prematurely or situations where
many of the pageblocks encountered by the free scanner are almost full
instead of being properly packed. Previous testing had indicated that
without this patch there were occasional large spikes in the free
scanner without this patch.
[dan.carpenter@oracle.com: fix static checker warning]
Link: http://lkml.kernel.org/r/20190118175136.31341-20-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: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The fast isolation of free pages allows the cached PFN of the free
scanner to advance faster than necessary depending on the contents of
the free list. The key is that fast_isolate_freepages() can update
zone->compact_cached_free_pfn via isolate_freepages_block(). When the
fast search fails, the linear scan can start from a point that has
skipped valid migration targets, particularly pageblocks with just
low-order free pages. This can cause the migration source/target
scanners to meet prematurely causing a reset.
This patch starts by avoiding an update of the pageblock skip
information and cached PFN from isolate_freepages_block() and puts the
responsibility of updating that information in the callers. The fast
scanner will update the cached PFN if and only if it finds a block that
is higher than the existing cached PFN and sets the skip if the
pageblock is full or nearly full. The linear scanner will update
skipped information and the cached PFN only when a block is completely
scanned. The total impact is that the free scanner advances more slowly
as it is primarily driven by the linear scanner instead of the fast
search.
5.0.0-rc1 5.0.0-rc1
noresched-v3r17 slowfree-v3r17
Amean fault-both-3 2965.68 ( 0.00%) 3036.75 ( -2.40%)
Amean fault-both-5 3995.90 ( 0.00%) 4522.24 * -13.17%*
Amean fault-both-7 5842.12 ( 0.00%) 6365.35 ( -8.96%)
Amean fault-both-12 9550.87 ( 0.00%) 10340.93 ( -8.27%)
Amean fault-both-18 13304.72 ( 0.00%) 14732.46 ( -10.73%)
Amean fault-both-24 14618.59 ( 0.00%) 16288.96 ( -11.43%)
Amean fault-both-30 16650.96 ( 0.00%) 16346.21 ( 1.83%)
Amean fault-both-32 17145.15 ( 0.00%) 19317.49 ( -12.67%)
The impact to latency is higher than the last version but it appears to
be due to a slight increase in the free scan rates which is a potential
side-effect of the patch. However, this is necessary for later patches
that are more careful about how pageblocks are treated as earlier
iterations of those patches hit corner cases where the restarts were
punishing and very visible.
Link: http://lkml.kernel.org/r/20190118175136.31341-19-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: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Scanning on large machines can take a considerable length of time and
eventually need to be rescheduled. This is treated as an abort event
but that's not appropriate as the attempt is likely to be retried after
making numerous checks and taking another cycle through the page
allocator. This patch will check the need to reschedule if necessary
but continue the scanning.
The main benefit is reduced scanning when compaction is taking a long
time or the machine is over-saturated. It also avoids an unnecessary
exit of compaction that ends up being retried by the page allocator in
the outer loop.
5.0.0-rc1 5.0.0-rc1
synccached-v3r16 noresched-v3r17
Amean fault-both-1 0.00 ( 0.00%) 0.00 * 0.00%*
Amean fault-both-3 2958.27 ( 0.00%) 2965.68 ( -0.25%)
Amean fault-both-5 4091.90 ( 0.00%) 3995.90 ( 2.35%)
Amean fault-both-7 5803.05 ( 0.00%) 5842.12 ( -0.67%)
Amean fault-both-12 9481.06 ( 0.00%) 9550.87 ( -0.74%)
Amean fault-both-18 14141.51 ( 0.00%) 13304.72 ( 5.92%)
Amean fault-both-24 16438.00 ( 0.00%) 14618.59 ( 11.07%)
Amean fault-both-30 17531.72 ( 0.00%) 16650.96 ( 5.02%)
Amean fault-both-32 17101.96 ( 0.00%) 17145.15 ( -0.25%)
Link: http://lkml.kernel.org/r/20190118175136.31341-18-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: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
With incremental changes, compact_should_abort no longer makes any
documented sense. Rename to compact_check_resched and update the
associated comments. There is no benefit other than reducing redundant
code and making the intent slightly clearer. It could potentially be
merged with earlier patches but it just makes the review slightly
harder.
Link: http://lkml.kernel.org/r/20190118175136.31341-17-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: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Migrate has separate cached PFNs for ASYNC and SYNC* migration on the
basis that some migrations will fail in ASYNC mode. However, if the
cached PFNs match at the start of scanning and pageblocks are skipped
due to having no isolation candidates, then the sync state does not
matter. This patch keeps matching cached PFNs in sync until a pageblock
with isolation candidates is found.
The actual benefit is marginal given that the sync scanner following the
async scanner will often skip a number of pageblocks but it's useless
work. Any benefit depends heavily on whether the scanners restarted
recently.
Link: http://lkml.kernel.org/r/20190118175136.31341-16-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: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When scanning for sources or targets, PageCompound is checked for huge
pages as they can be skipped quickly but it happens relatively late
after a lot of setup and checking. This patch short-cuts the check to
make it earlier. It might still change when the lock is acquired but
this has less overhead overall. The free scanner advances but the
migration scanner does not. Typically the free scanner encounters more
movable blocks that change state over the lifetime of the system and
also tends to scan more aggressively as it's actively filling its
portion of the physical address space with data. This could change in
the future but for the moment, this worked better in practice and
incurred fewer scan restarts.
The impact on latency and allocation success rates is marginal but the
free scan rates are reduced by 15% and system CPU usage is reduced by
3.3%. The 2-socket results are not materially different.
Link: http://lkml.kernel.org/r/20190118175136.31341-15-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: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Async migration aborts on spinlock contention but contention can be high
when there are multiple compaction attempts and kswapd is active. The
consequence is that the migration scanners move forward uselessly while
still contending on locks for longer while leaving suitable migration
sources behind.
This patch will acquire the lock but track when contention occurs. When
it does, the current pageblock will finish as compaction may succeed for
that block and then abort. This will have a variable impact on latency
as in some cases useless scanning is avoided (reduces latency) but a
lock will be contended (increase latency) or a single contended
pageblock is scanned that would otherwise have been skipped (increase
latency).
5.0.0-rc1 5.0.0-rc1
norescan-v3r16 finishcontend-v3r16
Amean fault-both-1 0.00 ( 0.00%) 0.00 * 0.00%*
Amean fault-both-3 3002.07 ( 0.00%) 3153.17 ( -5.03%)
Amean fault-both-5 4684.47 ( 0.00%) 4280.52 ( 8.62%)
Amean fault-both-7 6815.54 ( 0.00%) 5811.50 * 14.73%*
Amean fault-both-12 10864.02 ( 0.00%) 9276.85 ( 14.61%)
Amean fault-both-18 12247.52 ( 0.00%) 11032.67 ( 9.92%)
Amean fault-both-24 15683.99 ( 0.00%) 14285.70 ( 8.92%)
Amean fault-both-30 18620.02 ( 0.00%) 16293.76 * 12.49%*
Amean fault-both-32 19250.28 ( 0.00%) 16721.02 * 13.14%*
5.0.0-rc1 5.0.0-rc1
norescan-v3r16 finishcontend-v3r16
Percentage huge-1 0.00 ( 0.00%) 0.00 ( 0.00%)
Percentage huge-3 95.00 ( 0.00%) 96.82 ( 1.92%)
Percentage huge-5 94.22 ( 0.00%) 95.40 ( 1.26%)
Percentage huge-7 92.35 ( 0.00%) 95.92 ( 3.86%)
Percentage huge-12 91.90 ( 0.00%) 96.73 ( 5.25%)
Percentage huge-18 89.58 ( 0.00%) 96.77 ( 8.03%)
Percentage huge-24 90.03 ( 0.00%) 96.05 ( 6.69%)
Percentage huge-30 89.14 ( 0.00%) 96.81 ( 8.60%)
Percentage huge-32 90.58 ( 0.00%) 97.41 ( 7.54%)
There is a variable impact that is mostly good on latency while allocation
success rates are slightly higher. System CPU usage is reduced by about
10% but scan rate impact is mixed
Compaction migrate scanned 27997659.00 20148867
Compaction free scanned 120782791.00 118324914
Migration scan rates are reduced 28% which is expected as a pageblock is
used by the async scanner instead of skipped. The impact on the free
scanner is known to be variable. Overall the primary justification for
this patch is that completing scanning of a pageblock is very important
for later patches.
[yuehaibing@huawei.com: fix unused variable warning]
Link: http://lkml.kernel.org/r/20190118175136.31341-14-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: YueHaibing <yuehaibing@huawei.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pageblocks are marked for skip when no pages are isolated after a scan.
However, it's possible to hit corner cases where the migration scanner
gets stuck near the boundary between the source and target scanner. Due
to pages being migrated in blocks of COMPACT_CLUSTER_MAX, pages that are
migrated can be reallocated before the pageblock is complete. The
pageblock is not necessarily skipped so it can be rescanned multiple
times. Similarly, a pageblock with some dirty/writeback pages may fail
to migrate and be rescanned until writeback completes which is wasteful.
This patch tracks if a pageblock is being rescanned. If so, then the
entire pageblock will be migrated as one operation. This narrows the
race window during which pages can be reallocated during migration.
Secondly, if there are pages that cannot be isolated then the pageblock
will still be fully scanned and marked for skipping. On the second
rescan, the pageblock skip is set and the migration scanner makes
progress.
5.0.0-rc1 5.0.0-rc1
findfree-v3r16 norescan-v3r16
Amean fault-both-1 0.00 ( 0.00%) 0.00 * 0.00%*
Amean fault-both-3 3200.68 ( 0.00%) 3002.07 ( 6.21%)
Amean fault-both-5 4847.75 ( 0.00%) 4684.47 ( 3.37%)
Amean fault-both-7 6658.92 ( 0.00%) 6815.54 ( -2.35%)
Amean fault-both-12 11077.62 ( 0.00%) 10864.02 ( 1.93%)
Amean fault-both-18 12403.97 ( 0.00%) 12247.52 ( 1.26%)
Amean fault-both-24 15607.10 ( 0.00%) 15683.99 ( -0.49%)
Amean fault-both-30 18752.27 ( 0.00%) 18620.02 ( 0.71%)
Amean fault-both-32 21207.54 ( 0.00%) 19250.28 * 9.23%*
5.0.0-rc1 5.0.0-rc1
findfree-v3r16 norescan-v3r16
Percentage huge-3 96.86 ( 0.00%) 95.00 ( -1.91%)
Percentage huge-5 93.72 ( 0.00%) 94.22 ( 0.53%)
Percentage huge-7 94.31 ( 0.00%) 92.35 ( -2.08%)
Percentage huge-12 92.66 ( 0.00%) 91.90 ( -0.82%)
Percentage huge-18 91.51 ( 0.00%) 89.58 ( -2.11%)
Percentage huge-24 90.50 ( 0.00%) 90.03 ( -0.52%)
Percentage huge-30 91.57 ( 0.00%) 89.14 ( -2.65%)
Percentage huge-32 91.00 ( 0.00%) 90.58 ( -0.46%)
Negligible difference but this was likely a case when the specific
corner case was not hit. A previous run of the same patch based on an
earlier iteration of the series showed large differences where migration
rates could be halved when the corner case was hit.
The specific corner case where migration scan rates go through the roof
was due to a dirty/writeback pageblock located at the boundary of the
migration/free scanner did not happen in this case. When it does
happen, the scan rates multipled by massive margins.
Link: http://lkml.kernel.org/r/20190118175136.31341-13-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: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Similar to the migration scanner, this patch uses the free lists to
quickly locate a migration target. The search is different in that
lower orders will be searched for a suitable high PFN if necessary but
the search is still bound. This is justified on the grounds that the
free scanner typically scans linearly much more than the migration
scanner.
If a free page is found, it is isolated and compaction continues if
enough pages were isolated. For SYNC* scanning, the full pageblock is
scanned for any remaining free pages so that is can be marked for
skipping in the near future.
1-socket thpfioscale
5.0.0-rc1 5.0.0-rc1
isolmig-v3r15 findfree-v3r16
Amean fault-both-3 3024.41 ( 0.00%) 3200.68 ( -5.83%)
Amean fault-both-5 4749.30 ( 0.00%) 4847.75 ( -2.07%)
Amean fault-both-7 6454.95 ( 0.00%) 6658.92 ( -3.16%)
Amean fault-both-12 10324.83 ( 0.00%) 11077.62 ( -7.29%)
Amean fault-both-18 12896.82 ( 0.00%) 12403.97 ( 3.82%)
Amean fault-both-24 13470.60 ( 0.00%) 15607.10 * -15.86%*
Amean fault-both-30 17143.99 ( 0.00%) 18752.27 ( -9.38%)
Amean fault-both-32 17743.91 ( 0.00%) 21207.54 * -19.52%*
The impact on latency is variable but the search is optimistic and
sensitive to the exact system state. Success rates are similar but the
major impact is to the rate of scanning
5.0.0-rc1 5.0.0-rc1
isolmig-v3r15 findfree-v3r16
Compaction migrate scanned 25646769 29507205
Compaction free scanned 201558184 100359571
The free scan rates are reduced by 50%. The 2-socket reductions for the
free scanner are more dramatic which is a likely reflection that the
machine has more memory.
[dan.carpenter@oracle.com: fix static checker warning]
[vbabka@suse.cz: correct number of pages scanned for lower orders]
Link: http://lkml.kernel.org/r/20190118175136.31341-12-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Due to either a fast search of the free list or a linear scan, it is
possible for multiple compaction instances to pick the same pageblock
for migration. This is lucky for one scanner and increased scanning for
all the others. It also allows a race between requests on which first
allocates the resulting free block.
This patch tests and updates the pageblock skip for the migration
scanner carefully. When isolating a block, it will check and skip if
the block is already in use. Once the zone lock is acquired, it will be
rechecked so that only one scanner can set the pageblock skip for
exclusive use. Any scanner contending will continue with a linear scan.
The skip bit is still set if no pages can be isolated in a range. While
this may result in redundant scanning, it avoids unnecessarily acquiring
the zone lock when there are no suitable migration sources.
1-socket thpscale
Amean fault-both-1 0.00 ( 0.00%) 0.00 * 0.00%*
Amean fault-both-3 3390.40 ( 0.00%) 3024.41 ( 10.80%)
Amean fault-both-5 5082.28 ( 0.00%) 4749.30 ( 6.55%)
Amean fault-both-7 7012.51 ( 0.00%) 6454.95 ( 7.95%)
Amean fault-both-12 11346.63 ( 0.00%) 10324.83 ( 9.01%)
Amean fault-both-18 15324.19 ( 0.00%) 12896.82 * 15.84%*
Amean fault-both-24 16088.50 ( 0.00%) 13470.60 * 16.27%*
Amean fault-both-30 18723.42 ( 0.00%) 17143.99 ( 8.44%)
Amean fault-both-32 18612.01 ( 0.00%) 17743.91 ( 4.66%)
5.0.0-rc1 5.0.0-rc1
findmig-v3r15 isolmig-v3r15
Percentage huge-3 89.83 ( 0.00%) 92.96 ( 3.48%)
Percentage huge-5 91.96 ( 0.00%) 93.26 ( 1.41%)
Percentage huge-7 92.85 ( 0.00%) 93.63 ( 0.84%)
Percentage huge-12 92.74 ( 0.00%) 92.80 ( 0.07%)
Percentage huge-18 91.71 ( 0.00%) 91.62 ( -0.10%)
Percentage huge-24 92.13 ( 0.00%) 91.50 ( -0.69%)
Percentage huge-30 93.79 ( 0.00%) 92.73 ( -1.13%)
Percentage huge-32 91.27 ( 0.00%) 91.94 ( 0.74%)
This shows a reasonable reduction in latency as multiple compaction
scanners do not operate on the same blocks with a similar allocation
success rate.
Compaction migrate scanned 41093126 25646769
Migration scan rates are reduced by 38%.
Link: http://lkml.kernel.org/r/20190118175136.31341-11-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: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The migration scanner is a linear scan of a zone with a potentiall large
search space. Furthermore, many pageblocks are unusable such as those
filled with reserved pages or partially filled with pages that cannot
migrate. These still get scanned in the common case of allocating a THP
and the cost accumulates.
The patch uses a partial search of the free lists to locate a migration
source candidate that is marked as MOVABLE when allocating a THP. It
prefers picking a block with a larger number of free pages already on
the basis that there are fewer pages to migrate to free the entire
block. The lowest PFN found during searches is tracked as the basis of
the start for the linear search after the first search of the free list
fails. After the search, the free list is shuffled so that the next
search will not encounter the same page. If the search fails then the
subsequent searches will be shorter and the linear scanner is used.
If this search fails, or if the request is for a small or
unmovable/reclaimable allocation then the linear scanner is still used.
It is somewhat pointless to use the list search in those cases. Small
free pages must be used for the search and there is no guarantee that
movable pages are located within that block that are contiguous.
5.0.0-rc1 5.0.0-rc1
noboost-v3r10 findmig-v3r15
Amean fault-both-3 3771.41 ( 0.00%) 3390.40 ( 10.10%)
Amean fault-both-5 5409.05 ( 0.00%) 5082.28 ( 6.04%)
Amean fault-both-7 7040.74 ( 0.00%) 7012.51 ( 0.40%)
Amean fault-both-12 11887.35 ( 0.00%) 11346.63 ( 4.55%)
Amean fault-both-18 16718.19 ( 0.00%) 15324.19 ( 8.34%)
Amean fault-both-24 21157.19 ( 0.00%) 16088.50 * 23.96%*
Amean fault-both-30 21175.92 ( 0.00%) 18723.42 * 11.58%*
Amean fault-both-32 21339.03 ( 0.00%) 18612.01 * 12.78%*
5.0.0-rc1 5.0.0-rc1
noboost-v3r10 findmig-v3r15
Percentage huge-3 86.50 ( 0.00%) 89.83 ( 3.85%)
Percentage huge-5 92.52 ( 0.00%) 91.96 ( -0.61%)
Percentage huge-7 92.44 ( 0.00%) 92.85 ( 0.44%)
Percentage huge-12 92.98 ( 0.00%) 92.74 ( -0.25%)
Percentage huge-18 91.70 ( 0.00%) 91.71 ( 0.02%)
Percentage huge-24 91.59 ( 0.00%) 92.13 ( 0.60%)
Percentage huge-30 90.14 ( 0.00%) 93.79 ( 4.04%)
Percentage huge-32 90.03 ( 0.00%) 91.27 ( 1.37%)
This shows an improvement in allocation latencies with similar
allocation success rates. While not presented, there was a 31%
reduction in migration scanning and a 8% reduction on system CPU usage.
A 2-socket machine showed similar benefits.
[mgorman@techsingularity.net: several fixes]
Link: http://lkml.kernel.org/r/20190204120111.GL9565@techsingularity.net
[vbabka@suse.cz: migrate block that was found-fast, some optimisations]
Link: http://lkml.kernel.org/r/20190118175136.31341-10-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: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When compaction is finishing, it uses a flag to ensure the pageblock is
complete but it makes sense to always complete migration of a pageblock.
Minimally, skip information is based on a pageblock and partially
scanned pageblocks may incur more scanning in the future. The pageblock
skip handling also becomes more strict later in the series and the hint
is more useful if a complete pageblock was always scanned.
The potentially impacts latency as more scanning is done but it's not a
consistent win or loss as the scanning is not always a high percentage
of the pageblock and sometimes it is offset by future reductions in
scanning. Hence, the results are not presented this time due to a
misleading mix of gains/losses without any clear pattern. However, full
scanning of the pageblock is important for later patches.
Link: http://lkml.kernel.org/r/20190118175136.31341-8-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: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It's non-obvious that high-order free pages are split into order-0 pages
from the function name. Fix it.
Link: http://lkml.kernel.org/r/20190118175136.31341-6-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: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
A zone parameter is passed into a number of top-level compaction
functions despite the fact that it's already in compact_control. This
is harmless but it did need an audit to check if zone actually ever
changes meaningfully. This patches removes the parameter in a number of
top-level functions. The change could be much deeper but this was
enough to briefly clarify the flow.
No functional change.
Link: http://lkml.kernel.org/r/20190118175136.31341-5-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: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The last_migrated_pfn field is a bit dubious as to whether it really
helps but either way, the information from it can be inferred without
increasing the size of compact_control so remove the field.
Link: http://lkml.kernel.org/r/20190118175136.31341-4-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: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
sysctl_extfrag_handler() neglects to propagate the return value from
proc_dointvec_minmax() to its caller. It's a wrapper that doesn't need
to exist, so just use proc_dointvec_minmax() directly.
Link: http://lkml.kernel.org/r/20190104032557.3056-1-willy@infradead.org
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reported-by: Aditya Pakki <pakki001@umn.edu>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
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>
When systems are overcommitted and resources become contended, it's hard
to tell exactly the impact this has on workload productivity, or how close
the system is to lockups and OOM kills. In particular, when machines work
multiple jobs concurrently, the impact of overcommit in terms of latency
and throughput on the individual job can be enormous.
In order to maximize hardware utilization without sacrificing individual
job health or risk complete machine lockups, this patch implements a way
to quantify resource pressure in the system.
A kernel built with CONFIG_PSI=y creates files in /proc/pressure/ that
expose the percentage of time the system is stalled on CPU, memory, or IO,
respectively. Stall states are aggregate versions of the per-task delay
accounting delays:
cpu: some tasks are runnable but not executing on a CPU
memory: tasks are reclaiming, or waiting for swapin or thrashing cache
io: tasks are waiting for io completions
These percentages of walltime can be thought of as pressure percentages,
and they give a general sense of system health and productivity loss
incurred by resource overcommit. They can also indicate when the system
is approaching lockup scenarios and OOMs.
To do this, psi keeps track of the task states associated with each CPU
and samples the time they spend in stall states. Every 2 seconds, the
samples are averaged across CPUs - weighted by the CPUs' non-idle time to
eliminate artifacts from unused CPUs - and translated into percentages of
walltime. A running average of those percentages is maintained over 10s,
1m, and 5m periods (similar to the loadaverage).
[hannes@cmpxchg.org: doc fixlet, per Randy]
Link: http://lkml.kernel.org/r/20180828205625.GA14030@cmpxchg.org
[hannes@cmpxchg.org: code optimization]
Link: http://lkml.kernel.org/r/20180907175015.GA8479@cmpxchg.org
[hannes@cmpxchg.org: rename psi_clock() to psi_update_work(), per Peter]
Link: http://lkml.kernel.org/r/20180907145404.GB11088@cmpxchg.org
[hannes@cmpxchg.org: fix build]
Link: http://lkml.kernel.org/r/20180913014222.GA2370@cmpxchg.org
Link: http://lkml.kernel.org/r/20180828172258.3185-9-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Daniel Drake <drake@endlessm.com>
Tested-by: Suren Baghdasaryan <surenb@google.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <jweiner@fb.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Enderborg <peter.enderborg@sony.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/*.c files use symbolic and octal styles for permissions.
Using octal and not symbolic permissions is preferred by many as more
readable.
https://lkml.org/lkml/2016/8/2/1945
Prefer the direct use of octal for permissions.
Done using
$ scripts/checkpatch.pl -f --types=SYMBOLIC_PERMS --fix-inplace mm/*.c
and some typing.
Before: $ git grep -P -w "0[0-7]{3,3}" mm | wc -l
44
After: $ git grep -P -w "0[0-7]{3,3}" mm | wc -l
86
Miscellanea:
o Whitespace neatening around these conversions.
Link: http://lkml.kernel.org/r/2e032ef111eebcd4c5952bae86763b541d373469.1522102887.git.joe@perches.com
Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This reverts the following commits that change CMA design in MM.
3d2054ad8c ("ARM: CMA: avoid double mapping to the CMA area if CONFIG_HIGHMEM=y")
1d47a3ec09 ("mm/cma: remove ALLOC_CMA")
bad8c6c0b1 ("mm/cma: manage the memory of the CMA area by using the ZONE_MOVABLE")
Ville reported a following error on i386.
Inode-cache hash table entries: 65536 (order: 6, 262144 bytes)
microcode: microcode updated early to revision 0x4, date = 2013-06-28
Initializing CPU#0
Initializing HighMem for node 0 (000377fe:00118000)
Initializing Movable for node 0 (00000001:00118000)
BUG: Bad page state in process swapper pfn:377fe
page:f53effc0 count:0 mapcount:-127 mapping:00000000 index:0x0
flags: 0x80000000()
raw: 80000000 00000000 00000000 ffffff80 00000000 00000100 00000200 00000001
page dumped because: nonzero mapcount
Modules linked in:
CPU: 0 PID: 0 Comm: swapper Not tainted 4.17.0-rc5-elk+ #145
Hardware name: Dell Inc. Latitude E5410/03VXMC, BIOS A15 07/11/2013
Call Trace:
dump_stack+0x60/0x96
bad_page+0x9a/0x100
free_pages_check_bad+0x3f/0x60
free_pcppages_bulk+0x29d/0x5b0
free_unref_page_commit+0x84/0xb0
free_unref_page+0x3e/0x70
__free_pages+0x1d/0x20
free_highmem_page+0x19/0x40
add_highpages_with_active_regions+0xab/0xeb
set_highmem_pages_init+0x66/0x73
mem_init+0x1b/0x1d7
start_kernel+0x17a/0x363
i386_start_kernel+0x95/0x99
startup_32_smp+0x164/0x168
The reason for this error is that the span of MOVABLE_ZONE is extended
to whole node span for future CMA initialization, and, normal memory is
wrongly freed here. I submitted the fix and it seems to work, but,
another problem happened.
It's so late time to fix the later problem so I decide to reverting the
series.
Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Laura Abbott <labbott@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now, all reserved pages for CMA region are belong to the ZONE_MOVABLE
and it only serves for a request with GFP_HIGHMEM && GFP_MOVABLE.
Therefore, we don't need to maintain ALLOC_CMA at all.
Link: http://lkml.kernel.org/r/1512114786-5085-3-git-send-email-iamjoonsoo.kim@lge.com
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Tested-by: Tony Lindgren <tony@atomide.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Laura Abbott <lauraa@codeaurora.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
No allocation callback is using this argument anymore. new_page_node
used to use this parameter to convey node_id resp. migration error up
to move_pages code (do_move_page_to_node_array). The error status never
made it into the final status field and we have a better way to
communicate node id to the status field now. All other allocation
callbacks simply ignored the argument so we can drop it finally.
[mhocko@suse.com: fix migration callback]
Link: http://lkml.kernel.org/r/20180105085259.GH2801@dhcp22.suse.cz
[akpm@linux-foundation.org: fix alloc_misplaced_dst_page()]
[mhocko@kernel.org: fix build]
Link: http://lkml.kernel.org/r/20180103091134.GB11319@dhcp22.suse.cz
Link: http://lkml.kernel.org/r/20180103082555.14592-3-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Zi Yan <zi.yan@cs.rutgers.edu>
Cc: Andrea Reale <ar@linux.vnet.ibm.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It's possible for free pages to become stranded on per-cpu pagesets
(pcps) that, if drained, could be merged with buddy pages on the zone's
free area to form large order pages, including up to MAX_ORDER.
Consider a verbose example using the tools/vm/page-types tool at the
beginning of a ZONE_NORMAL ('B' indicates a buddy page and 'S' indicates
a slab page). Pages on pcps do not have any page flags set.
109954 1 _______S________________________________________________________
109955 2 __________B_____________________________________________________
109957 1 ________________________________________________________________
109958 1 __________B_____________________________________________________
109959 7 ________________________________________________________________
109960 1 __________B_____________________________________________________
109961 9 ________________________________________________________________
10996a 1 __________B_____________________________________________________
10996b 3 ________________________________________________________________
10996e 1 __________B_____________________________________________________
10996f 1 ________________________________________________________________
...
109f8c 1 __________B_____________________________________________________
109f8d 2 ________________________________________________________________
109f8f 2 __________B_____________________________________________________
109f91 f ________________________________________________________________
109fa0 1 __________B_____________________________________________________
109fa1 7 ________________________________________________________________
109fa8 1 __________B_____________________________________________________
109fa9 1 ________________________________________________________________
109faa 1 __________B_____________________________________________________
109fab 1 _______S________________________________________________________
The compaction migration scanner is attempting to defragment this memory
since it is at the beginning of the zone. It has done so quite well,
all movable pages have been migrated. From pfn [0x109955, 0x109fab),
there are only buddy pages and pages without flags set.
These pages may be stranded on pcps that could otherwise allow this
memory to be coalesced if freed back to the zone free area. It is
possible that some of these pages may not be on pcps and that something
has called alloc_pages() and used the memory directly, but we rely on
the absence of __GFP_MOVABLE in these cases to allocate from
MIGATE_UNMOVABLE pageblocks to try to keep these MIGRATE_MOVABLE
pageblocks as free as possible.
These buddy and pcp pages, spanning 1,621 pages, could be coalesced and
allow for three transparent hugepages to be dynamically allocated.
Running the numbers for all such spans on the system, it was found that
there were over 400 such spans of only buddy pages and pages without
flags set at the time this /proc/kpageflags sample was collected.
Without this support, there were _no_ order-9 or order-10 pages free.
When kcompactd fails to defragment memory such that a cc.order page can
be allocated, drain all pcps for the zone back to the buddy allocator so
this stranding cannot occur. Compaction for that order will
subsequently be deferred, which acts as a ratelimit on this drain.
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1803010340100.88270@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
"mode" argument is not used by try_to_compact_pages() and sub functions
anymore, it has been replaced by "prio". Fix the comment to explain the
use of "prio" argument.
Link: http://lkml.kernel.org/r/1515801336-20611-1-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit f3c931633a59 ("mm, compaction: persistently skip hugetlbfs
pageblocks") has introduced pageblock_skip_persistent() checks into
migration and free scanners, to make sure pageblocks that should be
persistently skipped are marked as such, regardless of the
ignore_skip_hint flag.
Since the previous patch introduced a new no_set_skip_hint flag, the
ignore flag no longer prevents marking pageblocks as skipped. Therefore
we can remove the special cases. The relevant pageblocks will be marked
as skipped by the common logic which marks each pageblock where no page
could be isolated. This makes the code simpler.
Link: http://lkml.kernel.org/r/20171102121706.21504-3-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pageblock skip hints were added as a heuristic for compaction, which
shares core code with CMA. Since CMA reliability would suffer from the
heuristics, compact_control flag ignore_skip_hint was added for the CMA
use case. Since 6815bf3f23 ("mm/compaction: respect ignore_skip_hint
in update_pageblock_skip") the flag also means that CMA won't *update*
the skip hints in addition to ignoring them.
Today, direct compaction can also ignore the skip hints in the last
resort attempt, but there's no reason not to set them when isolation
fails in such case. Thus, this patch splits off a new no_set_skip_hint
flag to avoid the updating, which only CMA sets. This should improve
the heuristics a bit, and allow us to simplify the persistent skip bit
handling as the next step.
Link: http://lkml.kernel.org/r/20171102121706.21504-2-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
pageblock_skip_persistent() checks for HugeTLB pages of pageblock order.
When clearing pageblock skip bits for compaction, the bits are not
cleared for such pageblocks, because they cannot contain base pages
suitable for migration, nor free pages to use as migration targets.
This optimization can be simply extended to all compound pages of order
equal or larger than pageblock order, because migrating such pages (if
they support it) cannot help sub-pageblock fragmentation. This includes
THP's and also gigantic HugeTLB pages, which the current implementation
doesn't persistently skip due to a strict pageblock_order equality check
and not recognizing tail pages.
While THP pages are generally less "persistent" than HugeTLB, we can
still expect that if a THP exists at the point of
__reset_isolation_suitable(), it will exist also during the subsequent
compaction run. The time difference here could be actually smaller than
between a compaction run that sets a (non-persistent) skip bit on a THP,
and the next compaction run that observes it.
Link: http://lkml.kernel.org/r/20171102121706.21504-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It is pointless to migrate hugetlb memory as part of memory compaction
if the hugetlb size is equal to the pageblock order. No defragmentation
is occurring in this condition.
It is also pointless to for the freeing scanner to scan a pageblock
where a hugetlb page is pinned. Unconditionally skip these pageblocks,
and do so peristently so that they are not rescanned until it is
observed that these hugepages are no longer pinned.
It would also be possible to do this by involving the hugetlb subsystem
in marking pageblocks to no longer be skipped when they hugetlb pages
are freed. This is a simple solution that doesn't involve any
additional subsystems in pageblock skip manipulation.
[rientjes@google.com: fix build]
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1708201734390.117182@chino.kir.corp.google.com
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1708151639130.106658@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
Tested-by: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Kcompactd is needlessly ignoring pageblock skip information. It is
doing MIGRATE_SYNC_LIGHT compaction, which is no more powerful than
MIGRATE_SYNC compaction.
If compaction recently failed to isolate memory from a set of
pageblocks, there is nothing to indicate that kcompactd will be able to
do so, or that it is beneficial from attempting to isolate memory.
Use the pageblock skip hint to avoid rescanning pageblocks needlessly
until that information is reset.
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1708151638550.106658@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.
By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.
How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,
Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.
The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.
The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.
Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).
All documentation files were explicitly excluded.
The following heuristics were used to determine which SPDX license
identifiers to apply.
- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.
For non */uapi/* files that summary was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139
and resulted in the first patch in this series.
If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930
and resulted in the second patch in this series.
- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:
SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1
and that resulted in the third patch in this series.
- when the two scanners agreed on the detected license(s), that became
the concluded license(s).
- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.
- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).
- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.
- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.
In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.
Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.
Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.
In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.
Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct
This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.
These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Andrea brought to my attention that the L->{L,S} guarantees are
completely bogus for this case. I was looking at the diagram, from the
offending commit, when that _is_ the race, we had the load reordered
already.
What we need is at least S->L semantics, thus simply use
wq_has_sleeper() to serialize the call for good.
Link: http://lkml.kernel.org/r/20170914175313.GB811@linux-80c1.suse
Fixes: 46acef048a (mm,compaction: serialize waitqueue_active() checks)
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Reported-by: Andrea Parri <parri.andrea@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
__reset_isolation_suitable walks the whole zone pfn range and it tries
to jump over holes by checking the zone for each page. It might still
stumble over offline pages, though. Skip those by checking
pfn_to_online_page()
Link: http://lkml.kernel.org/r/20170515085827.16474-9-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Daniel Kiper <daniel.kiper@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Reza Arbab <arbab@linux.vnet.ibm.com>
Cc: Tobias Regnery <tobias.regnery@gmail.com>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The main goal of direct compaction is to form a high-order page for
allocation, but it should also help against long-term fragmentation when
possible.
Most lower-than-pageblock-order compactions are for non-movable
allocations, which means that if we compact in a movable pageblock and
terminate as soon as we create the high-order page, it's unlikely that
the fallback heuristics will claim the whole block. Instead there might
be a single unmovable page in a pageblock full of movable pages, and the
next unmovable allocation might pick another pageblock and increase
long-term fragmentation.
To help against such scenarios, this patch changes the termination
criteria for compaction so that the current pageblock is finished even
though the high-order page already exists. Note that it might be
possible that the high-order page formed elsewhere in the zone due to
parallel activity, but this patch doesn't try to detect that.
This is only done with sync compaction, because async compaction is
limited to pageblock of the same migratetype, where it cannot result in
a migratetype fallback. (Async compaction also eagerly skips
order-aligned blocks where isolation fails, which is against the goal of
migrating away as much of the pageblock as possible.)
As a result of this patch, long-term memory fragmentation should be
reduced.
In testing based on 4.9 kernel with stress-highalloc from mmtests
configured for order-4 GFP_KERNEL allocations, this patch has reduced
the number of unmovable allocations falling back to movable pageblocks
by 20%. The number
Link: http://lkml.kernel.org/r/20170307131545.28577-9-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The migrate scanner in async compaction is currently limited to
MIGRATE_MOVABLE pageblocks. This is a heuristic intended to reduce
latency, based on the assumption that non-MOVABLE pageblocks are
unlikely to contain movable pages.
However, with the exception of THP's, most high-order allocations are
not movable. Should the async compaction succeed, this increases the
chance that the non-MOVABLE allocations will fallback to a MOVABLE
pageblock, making the long-term fragmentation worse.
This patch attempts to help the situation by changing async direct
compaction so that the migrate scanner only scans the pageblocks of the
requested migratetype. If it's a non-MOVABLE type and there are such
pageblocks that do contain movable pages, chances are that the
allocation can succeed within one of such pageblocks, removing the need
for a fallback. If that fails, the subsequent sync attempt will ignore
this restriction.
In testing based on 4.9 kernel with stress-highalloc from mmtests
configured for order-4 GFP_KERNEL allocations, this patch has reduced
the number of unmovable allocations falling back to movable pageblocks
by 30%. The number of movable allocations falling back is reduced by
12%.
Link: http://lkml.kernel.org/r/20170307131545.28577-8-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Preparation patch. We are going to need migratetype at lower layers
than compact_zone() and compact_finished().
Link: http://lkml.kernel.org/r/20170307131545.28577-7-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Preparation for making the decisions more complex and depending on
compact_control flags. No functional change.
Link: http://lkml.kernel.org/r/20170307131545.28577-6-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When detecting whether compaction has succeeded in forming a high-order
page, __compact_finished() employs a watermark check, followed by an own
search for a suitable page in the freelists. This is not ideal for two
reasons:
- The watermark check also searches high-order freelists, but has a
less strict criteria wrt fallback. It's therefore redundant and waste
of cycles. This was different in the past when high-order watermark
check attempted to apply reserves to high-order pages.
- The watermark check might actually fail due to lack of order-0 pages.
Compaction can't help with that, so there's no point in continuing
because of that. It's possible that high-order page still exists and
it terminates.
This patch therefore removes the watermark check. This should save some
cycles and terminate compaction sooner in some cases.
Link: http://lkml.kernel.org/r/20170307131545.28577-3-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
By reviewing code, I find that if the migrate target is a large free
page and we ignore suitable, it may splite large target free page into
smaller block which is not good for defrag. So move the ignore block
suitable after check large free page.
As Vlastimil pointed out in RFC version that this patch is just based on
logical analyses which might be better for future-proofing the function
and it is most likely won't have any visible effect right now, for
direct compaction shouldn't have to be called if there's a
>=pageblock_order page already available.
Link: http://lkml.kernel.org/r/1489490743-5364-1-git-send-email-xieyisheng1@huawei.com
Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Hanjun Guo <guohanjun@huawei.com>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Suzuki K Poulose