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Filename Latest commit message Latest commit date
Roman Gushchin 9b6f7e163c mm: rework memcg kernel stack accounting 
If CONFIG_VMAP_STACK is set, kernel stacks are allocated using
__vmalloc_node_range() with __GFP_ACCOUNT.  So kernel stack pages are
charged against corresponding memory cgroups on allocation and uncharged
on releasing them.

The problem is that we do cache kernel stacks in small per-cpu caches and
do reuse them for new tasks, which can belong to different memory cgroups.

Each stack page still holds a reference to the original cgroup, so the
cgroup can't be released until the vmap area is released.

To make this happen we need more than two subsequent exits without forks
in between on the current cpu, which makes it very unlikely to happen.  As
a result, I saw a significant number of dying cgroups (in theory, up to 2
* number_of_cpu + number_of_tasks), which can't be released even by
significant memory pressure.

As a cgroup structure can take a significant amount of memory (first of
all, per-cpu data like memcg statistics), it leads to a noticeable waste
of memory.

Link: http://lkml.kernel.org/r/20180827162621.30187-1-guro@fb.com
Fixes: ac496bf48d ("fork: Optimize task creation by caching two thread stacks per CPU if CONFIG_VMAP_STACK=y")
Signed-off-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Michal Hocko <mhocko@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-10-26 16:25:19 -07:00
arch xtensa: use generic vga.h 2018-10-26 16:25:18 -07:00
block
certs
crypto
Documentation slub: extend slub debug to handle multiple slabs 2018-10-26 16:25:19 -07:00
drivers Char/Misc driver patches for 4.20-rc1 2018-10-26 09:11:43 -07:00
firmware
fs fs/iomap.c: change return type to vm_fault_t 2018-10-26 16:25:18 -07:00
include mm: rework memcg kernel stack accounting 2018-10-26 16:25:19 -07:00
init
ipc
kernel mm: rework memcg kernel stack accounting 2018-10-26 16:25:19 -07:00
lib lib/test_kasan.c: add tests for several string/memory API functions 2018-10-26 16:25:18 -07:00
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mm slub: extend slub debug to handle multiple slabs 2018-10-26 16:25:19 -07:00
net
samples Char/Misc driver patches for 4.20-rc1 2018-10-26 09:11:43 -07:00
scripts scripts/tags.sh: add DECLARE_HASHTABLE() 2018-10-26 16:25:18 -07:00
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MAINTAINERS Char/Misc driver patches for 4.20-rc1 2018-10-26 09:11:43 -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.