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Filename Latest commit message Latest commit date
Michal Koutný aeeddba9b4 mm/page_counter.c: fix protection usage propagation
commit a6f23d14ec7d7d02220ad8bb2774be3322b9aeec upstream.

When workload runs in cgroups that aren't directly below root cgroup and
their parent specifies reclaim protection, it may end up ineffective.

The reason is that propagate_protected_usage() is not called in all
hierarchy up.  All the protected usage is incorrectly accumulated in the
workload's parent.  This means that siblings_low_usage is overestimated
and effective protection underestimated.  Even though it is transitional
phenomenon (uncharge path does correct propagation and fixes the wrong
children_low_usage), it can undermine the intended protection
unexpectedly.

We have noticed this problem while seeing a swap out in a descendant of a
protected memcg (intermediate node) while the parent was conveniently
under its protection limit and the memory pressure was external to that
hierarchy.  Michal has pinpointed this down to the wrong
siblings_low_usage which led to the unwanted reclaim.

The fix is simply updating children_low_usage in respective ancestors also
in the charging path.

Fixes: 230671533d ("mm: memory.low hierarchical behavior")
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: <stable@vger.kernel.org>	[4.18+]
Link: http://lkml.kernel.org/r/20200803153231.15477-1-mhocko@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-08-21 13:05:27 +02:00
arch MIPS: qi_lb60: Fix routing to audio amplifier 2020-08-21 13:05:26 +02:00
block
certs
crypto
Documentation dt-bindings: iio: io-channel-mux: Fix compatible string in example code 2020-08-21 13:05:23 +02:00
drivers driver core: Avoid binding drivers to dead devices 2020-08-21 13:05:26 +02:00
fs ocfs2: change slot number type s16 to u16 2020-08-21 13:05:26 +02:00
include net/compat: Add missing sock updates for SCM_RIGHTS 2020-08-21 13:05:25 +02:00
init
ipc
kernel genirq/PM: Always unlock IRQ descriptor in rearm_wake_irq() 2020-08-21 13:05:20 +02:00
lib
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mm mm/page_counter.c: fix protection usage propagation 2020-08-21 13:05:27 +02:00
net mac80211: fix misplaced while instead of if 2020-08-21 13:05:26 +02:00
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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.