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Eric Dumazet cfcdef5e30 rcu: Allow rcu_do_batch() to dynamically adjust batch sizes
Bimodal behavior of rcu_do_batch() is not really suited to Google
applications like gfe servers.

When a process with millions of sockets exits, closing all files
queues two rcu callbacks per socket.

This eventually reaches the point where RCU enters an emergency
mode, where rcu_do_batch() do not return until whole queue is flushed.

Each rcu callback lasts at least 70 nsec, so with millions of
elements, we easily spend more than 100 msec without rescheduling.

Goal of this patch is to avoid the infamous message like following
"need_resched set for > 51999388 ns (52 ticks) without schedule"

We dynamically adjust the number of elements we process, instead
of 10 / INFINITE choices, we use a floor of ~1 % of current entries.

If the number is above 1000, we switch to a time based limit of 3 msec
per batch, adjustable with /sys/module/rcutree/parameters/rcu_resched_ns

Signed-off-by: Eric Dumazet <edumazet@google.com>
[ paulmck: Forward-port and remove debug statements. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-08-13 14:38:24 -07:00
Documentation rcu/nocb: Rename rcu_nocb_leader_stride kernel boot parameter 2019-08-13 14:32:39 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch Merge branches 'consolidate.2019.08.01b', 'fixes.2019.08.12a', 'lists.2019.08.13a' and 'torture.2019.08.01b' into HEAD 2019-08-13 14:30:30 -07:00
block for-linus-20190726-2 2019-07-26 19:20:34 -07:00
certs Revert "Merge tag 'keys-acl-20190703' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs" 2019-07-10 18:43:43 -07:00
crypto USB / PHY patches for 5.3-rc1 2019-07-11 15:40:06 -07:00
drivers acpi: Use built-in RCU list checking for acpi_ioremaps list 2019-08-13 14:29:22 -07:00
fs SPDX fixes for 5.3-rc2 2019-07-28 10:00:06 -07:00
include rcu/nocb: Atomic ->len field in rcu_segcblist structure 2019-08-13 14:35:49 -07:00
init Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
ipc Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
kernel rcu: Allow rcu_do_batch() to dynamically adjust batch sizes 2019-08-13 14:38:24 -07:00
lib test_firmware: fix a memory leak bug 2019-07-25 14:39:52 +02:00
mm mm/vmalloc: Sync unmappings in __purge_vmap_area_lazy() 2019-07-22 10:18:30 +02:00
net ipv4: Add lockdep condition to fix for_each_entry() 2019-08-09 11:01:08 -07:00
samples treewide: remove SPDX "WITH Linux-syscall-note" from kernel-space headers again 2019-07-25 11:05:10 +02:00
scripts Kbuild fixes for v5.3 2019-07-28 10:35:04 -07:00
security meminit fix 2019-07-28 12:33:15 -07:00
sound sound fixes for 5.3-rc2 2019-07-26 10:23:45 -07:00
tools rcutorture: Test TREE03 with the threadirqs kernel boot parameter 2019-08-01 14:30:22 -07:00
usr kbuild: enable arch/s390/include/uapi/asm/zcrypt.h for uapi header test 2019-07-23 10:45:46 +02:00
virt Documentation: move Documentation/virtual to Documentation/virt 2019-07-24 10:52:11 +02:00
.clang-format Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-17 11:26:25 -07:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore .gitignore: Add compilation database file 2019-07-27 12:18:19 +09:00
.mailmap MAINTAINERS: Update my email address 2019-07-22 14:57:50 +01:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Remove references to dead website. 2019-07-19 12:22:04 -07:00
Kbuild Kbuild updates for v5.1 2019-03-10 17:48:21 -07:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS MAINTAINERS: Update e-mail address for Andrea Parri 2019-08-12 11:25:06 -07:00
Makefile Linux 5.3-rc2 2019-07-28 12:47:02 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.