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Johannes Weiner 1a3e1f4096 mm: memcontrol: decouple reference counting from page accounting 
The reference counting of a memcg is currently coupled directly to how
many 4k pages are charged to it.  This doesn't work well with Roman's new
slab controller, which maintains pools of objects and doesn't want to keep
an extra balance sheet for the pages backing those objects.

This unusual refcounting design (reference counts usually track pointers
to an object) is only for historical reasons: memcg used to not take any
css references and simply stalled offlining until all charges had been
reparented and the page counters had dropped to zero.  When we got rid of
the reparenting requirement, the simple mechanical translation was to take
a reference for every charge.

More historical context can be found in commit e8ea14cc6e ("mm:
memcontrol: take a css reference for each charged page"), commit
64f2199389 ("mm: memcontrol: remove obsolete kmemcg pinning tricks") and
commit b2052564e6 ("mm: memcontrol: continue cache reclaim from offlined
groups").

The new slab controller exposes the limitations in this scheme, so let's
switch it to a more idiomatic reference counting model based on actual
kernel pointers to the memcg:

- The per-cpu stock holds a reference to the memcg its caching

- User pages hold a reference for their page->mem_cgroup. Transparent
  huge pages will no longer acquire tail references in advance, we'll
  get them if needed during the split.

- Kernel pages hold a reference for their page->mem_cgroup

- Pages allocated in the root cgroup will acquire and release css
  references for simplicity. css_get() and css_put() optimize that.

- The current memcg_charge_slab() already hacked around the per-charge
  references; this change gets rid of that as well.

- tcp accounting will handle reference in mem_cgroup_sk_{alloc,free}

Roman:
1) Rebased on top of the current mm tree: added css_get() in
   mem_cgroup_charge(), dropped mem_cgroup_try_charge() part
2) I've reformatted commit references in the commit log to make
   checkpatch.pl happy.

[hughd@google.com: remove css_put_many() from __mem_cgroup_clear_mc()]
  Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2007302011450.2347@eggly.anvils

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Link: http://lkml.kernel.org/r/20200623174037.3951353-6-guro@fb.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-08-07 11:33:24 -07:00
arch mm, treewide: rename kzfree() to kfree_sensitive() 2020-08-07 11:33:22 -07:00
block for-5.9/block-merge-20200804 2020-08-05 11:12:34 -07:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto mm, treewide: rename kzfree() to kfree_sensitive() 2020-08-07 11:33:22 -07:00
Documentation tmpfs: support 64-bit inums per-sb 2020-08-07 11:33:24 -07:00
drivers mm: memcg: convert vmstat slab counters to bytes 2020-08-07 11:33:24 -07:00
fs mm: memcg: convert vmstat slab counters to bytes 2020-08-07 11:33:24 -07:00
include mm: slub: implement SLUB version of obj_to_index() 2020-08-07 11:33:24 -07:00
init mm/slab: expand CONFIG_SLAB_FREELIST_HARDENED to include SLAB 2020-08-07 11:33:22 -07:00
ipc mmap locking API: use coccinelle to convert mmap_sem rwsem call sites 2020-06-09 09:39:14 -07:00
kernel mm: memcg: convert vmstat slab counters to bytes 2020-08-07 11:33:24 -07:00
lib mm, treewide: rename kzfree() to kfree_sensitive() 2020-08-07 11:33:22 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm mm: memcontrol: decouple reference counting from page accounting 2020-08-07 11:33:24 -07:00
net mm, treewide: rename kzfree() to kfree_sensitive() 2020-08-07 11:33:22 -07:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-08-05 20:13:21 -07:00
scripts mm, treewide: rename kzfree() to kfree_sensitive() 2020-08-07 11:33:22 -07:00
security mm, treewide: rename kzfree() to kfree_sensitive() 2020-08-07 11:33:22 -07:00
sound sound updates for 5.9 2020-08-06 14:27:31 -07:00
tools tools/testing/selftests/cgroup/cgroup_util.c: cg_read_strcmp: fix null pointer dereference 2020-08-07 11:33:21 -07:00
usr usr: Add support for zstd compressed initramfs 2020-07-31 11:49:08 +02:00
virt s390: implement diag318 2020-08-06 12:59:31 -07:00
.clang-format block: add bio_for_each_bvec_all() 2020-05-25 11:25:24 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: Add ZSTD-compressed files 2020-07-31 11:50:49 +02:00
.mailmap It's been a busy cycle for documentation - hopefully the busiest for a 2020-08-04 22:47:54 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS CREDITS: Replace HTTP links with HTTPS ones 2020-07-23 14:53:58 -06:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS TTY/Serial patches for 5.9-rc1 2020-08-06 14:56:11 -07:00
Makefile Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-08-05 20:13:21 -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.