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Shakeel Butt 60cada258d memcg: optimize memcg_rstat_updated
Currently the kernel maintains the stats updates per-memcg which is needed
to implement stats flushing threshold.  On the update side, the update is
added to the per-cpu per-memcg update of the given memcg and all of its
ancestors.  However when the given memcg has passed the flushing
threshold, all of its ancestors should have passed the threshold as well. 
There is no need to traverse up the memcg tree to maintain the stats
updates.

Perf profile collected from our fleet shows that memcg_rstat_updated is
one of the most expensive memcg function i.e.  a lot of cumulative CPU is
being spent on it.  So, even small micro optimizations matter a lot.  This
patch is microbenchmarked with multiple instances of netperf on a single
machine with locally running netserver and we see couple of percentage of
improvement.

Link: https://lkml.kernel.org/r/20250410025752.92159-1-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2025-05-11 17:48:29 -07:00
arch riscv: mm: call PUD/P4D ctor in special kernel pgtable alloc 2025-05-11 17:48:23 -07:00
block block-6.15-20250509 2025-05-09 10:34:50 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: scompress - increment scomp_scratch_users when already allocated 2025-04-25 10:33:30 +08:00
Documentation fs/proc: extend the PAGEMAP_SCAN ioctl to report guard regions 2025-05-11 17:48:16 -07:00
drivers zram: modernize writeback interface 2025-05-11 17:48:09 -07:00
fs fs/proc/page: refactor to reduce code duplication 2025-05-11 17:48:20 -07:00
include maple_tree: add sufficient height 2025-05-11 17:48:29 -07:00
init rust: clean Rust 1.88.0's unnecessary_transmutes lint 2025-05-07 00:11:47 +02:00
io_uring io_uring/sqpoll: Increase task_work submission batch size 2025-05-09 07:56:53 -06:00
ipc treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
kernel kernel/events/uprobes: uprobe_write_opcode() rewrite 2025-05-11 17:48:18 -07:00
lib maple_tree: reorder mas->store_type case statements 2025-05-11 17:48:29 -07:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm memcg: optimize memcg_rstat_updated 2025-05-11 17:48:29 -07:00
net net: export a helper for adding up queue stats 2025-05-08 11:56:12 +02:00
rust task: rust: rework how current is accessed 2025-05-11 17:48:25 -07:00
samples samples/bpf: Fix compilation failure for samples/bpf on LoongArch Fedora 2025-04-25 09:32:02 -07:00
scripts scripts: Do not strip .rela.dyn section 2025-05-08 12:01:01 +00:00
security Landlock fix for v6.15-rc4 2025-04-24 12:59:05 -07:00
sound ASoC: Fixes for v6.15 2025-05-01 10:22:20 +02:00
tools selftests/mm: restore default nr_hugepages value during cleanup in hugetlb_reparenting_test.sh 2025-05-11 17:48:29 -07:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-05 04:06:45 +09:00
virt ARM: 2025-04-08 13:47:55 -07:00
.clang-format clang-format: Update the ForEachMacros list for v6.15-rc1 2025-04-13 11:03:59 +02:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: Create intermediate vmlinux build with relocations preserved 2025-03-17 00:29:50 +09:00
.mailmap Input updates for v6.15-rc5 2025-05-11 10:29:29 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: update SLAB ALLOCATOR maintainers 2025-04-17 20:10:06 -07:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS tools/testing/selftests: assert that anon merge cases behave as expected 2025-05-11 17:48:26 -07:00
Makefile Linux 6.15-rc6 2025-05-11 14:54:11 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

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.