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af827e0904
The scan implementation for MGLRU was missing proportional reclaim
pressure for memcg, which contradicts the description in
Documentation/admin-guide/cgroup-v2.rst (memory.{low,min} section).
This issue can be observed in kselftest cgroup:test_memcontrol
(specifically test_memcg_min and test_memcg_low). The following table
shows the actual values observed in my local test env (on xfs) and the
error "e", which is the symmetric absolute percentage error from the ideal
values of 29M for c[0] and 21M for c[1].
test_memcg_min
| MGLRU enabled | MGLRU enabled | MGLRU disabled
| Without patch | With patch |
-----|-----------------|-----------------|---------------
c[0] | 25964544 (e=8%) | 28770304 (e=3%) | 27820032 (e=4%)
c[1] | 26214400 (e=9%) | 23998464 (e=4%) | 24776704 (e=6%)
test_memcg_low
| MGLRU enabled | MGLRU enabled | MGLRU disabled
| Without patch | With patch |
-----|-----------------|-----------------|---------------
c[0] | 26214400 (e=7%) | 27930624 (e=4%) | 27688960 (e=5%)
c[1] | 26214400 (e=9%) | 24764416 (e=6%) | 24920064 (e=6%)
Factor out the proportioning logic to a new function and have MGLRU reuse
it. While at it, update the eviction behavior via debugfs 'lru_gen'
interface ('-' command with an explicit 'nr_to_reclaim' parameter) to
ensure eviction is limited to the specified number.
Link: https://lkml.kernel.org/r/20250530162353.541882-1-den@valinux.co.jp
Signed-off-by: Koichiro Den <koichiro.den@canonical.com>
Reviewed-by: Yuanchu Xie <yuanchu@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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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 reStructuredText 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.