WSL2-Linux-Kernel

The source for the Linux kernel used in Windows Subsystem for Linux 2 (WSL2)

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Feng Tang c571686a92 mm/util.c: remove the VM_WARN_ONCE for vm_committed_as underflow check This check was added by commit `82f71ae4a2` ("mm: catch memory commitment underflow") in 2014 to have a safety check for issues which have been fixed. And there has been few report caught by it, as described in its commit log: : This shouldn't happen any more - the previous two patches fixed : the committed_as underflow issues. But it was really found by Qian Cai when he used the LTP memory stress suite to test a RFC patchset, which tries to improve scalability of per-cpu counter 'vm_committed_as', by chosing a bigger 'batch' number for loose overcommit policies (OVERCOMMIT_ALWAYS and OVERCOMMIT_GUESS), while keeping current number for OVERCOMMIT_NEVER. With that patchset, when system firstly uses a loose policy, the 'vm_committed_as' count could be a big negative value, as its big 'batch' number allows a big deviation, then when the policy is changed to OVERCOMMIT_NEVER, the 'batch' will be decreased to a much smaller value, thus hits this WARN check. To mitigate this, one proposed solution is to queue work on all online CPUs to do a local sync for 'vm_committed_as' when changing policy to OVERCOMMIT_NEVER, plus some global syncing to garante the case won't be hit. But this solution is costy and slow, given this check hasn't shown real trouble or benefit, simply drop it from one hot path of MM. And perf stats does show some tiny saving for removing it. Reported-by: Qian Cai <cai@lca.pw> Signed-off-by: Feng Tang <feng.tang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Qian Cai <cai@lca.pw> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: Andi Kleen <andi.kleen@intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Kees Cook <keescook@chromium.org> Link: http://lkml.kernel.org/r/20200603094804.GB89848@shbuild999.sh.intel.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2020-06-04 19:06:20 -07:00
Documentation	kcov: collect coverage from interrupts	2020-06-04 19:06:20 -07:00
LICENSES	…
arch	media updates for v5.8-rc1	2020-06-03 20:59:38 -07:00
block	…
certs	…
crypto	…
drivers	usb: core: kcov: collect coverage from usb complete callback	2020-06-04 19:06:20 -07:00
fs	Merge branch 'akpm' (patches from Andrew)	2020-06-03 20:24:15 -07:00
include	kcov: collect coverage from interrupts	2020-06-04 19:06:20 -07:00
init	Merge branch 'akpm' (patches from Andrew)	2020-06-03 20:24:15 -07:00
ipc	…
kernel	kcov: collect coverage from interrupts	2020-06-04 19:06:20 -07:00
lib	kcov: collect coverage from interrupts	2020-06-04 19:06:20 -07:00
mm	mm/util.c: remove the VM_WARN_ONCE for vm_committed_as underflow check	2020-06-04 19:06:20 -07:00
net	…
samples	…
scripts	…
security	…
sound	…
tools	Merge branch 'akpm' (patches from Andrew)	2020-06-03 20:24:15 -07:00
usr	…
virt	…
.clang-format	…
.cocciconfig	…
.get_maintainer.ignore	…
.gitattributes	…
.gitignore	…
.mailmap	…
COPYING	…
CREDITS	…
Kbuild	…
Kconfig	…
MAINTAINERS	media updates for v5.8-rc1	2020-06-03 20:59:38 -07:00
Makefile	…
README	…

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.