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Chengming Zhou dc4d1f3b53 sched/psi: report zeroes for CPU full at the system level 
[ Upstream commit 890d550d7d ]

Martin find it confusing when look at the /proc/pressure/cpu output,
and found no hint about that CPU "full" line in psi Documentation.

% cat /proc/pressure/cpu
some avg10=0.92 avg60=0.91 avg300=0.73 total=933490489
full avg10=0.22 avg60=0.23 avg300=0.16 total=358783277

The PSI_CPU_FULL state is introduced by commit e7fcd76228
("psi: Add PSI_CPU_FULL state"), which mainly for cgroup level,
but also counted at the system level as a side effect.

Naturally, the FULL state doesn't exist for the CPU resource at
the system level. These "full" numbers can come from CPU idle
schedule latency. For example, t1 is the time when task wakeup
on an idle CPU, t2 is the time when CPU pick and switch to it.
The delta of (t2 - t1) will be in CPU_FULL state.

Another case all processes can be stalled is when all cgroups
have been throttled at the same time, which unlikely to happen.

Anyway, CPU_FULL metric is meaningless and confusing at the
system level. So this patch will report zeroes for CPU full
at the system level, and update psi Documentation accordingly.

Fixes: e7fcd76228 ("psi: Add PSI_CPU_FULL state")
Reported-by: Martin Steigerwald <Martin.Steigerwald@proact.de>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/r/20220408121914.82855-1-zhouchengming@bytedance.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
 		2022-06-09 10:22:48 +02:00
Documentation sched/psi: report zeroes for CPU full at the system level 2022-06-09 10:22:48 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
arch signal: Deliver SIGTRAP on perf event asynchronously if blocked 2022-06-09 10:22:48 +02:00
block iocost: don't reset the inuse weight of under-weighted debtors 2022-05-09 09:14:31 +02:00
certs certs: Add support for using elliptic curve keys for signing modules 2021-08-23 19:55:42 +03:00
crypto crypto: ecrdsa - Fix incorrect use of vli_cmp 2022-06-06 08:43:39 +02:00
drivers drm/mediatek: dpi: Use mt8183 output formats for mt8192 2022-06-09 10:22:48 +02:00
fs smb3: check for null tcon 2022-06-09 10:22:43 +02:00
include signal: Deliver SIGTRAP on perf event asynchronously if blocked 2022-06-09 10:22:48 +02:00
init random: handle latent entropy and command line from random_init() 2022-05-30 09:29:16 +02:00
ipc ipc/sem: do not sleep with a spin lock held 2022-02-08 18:34:03 +01:00
kernel sched/psi: report zeroes for CPU full at the system level 2022-06-09 10:22:48 +02:00
lib lib/crypto: add prompts back to crypto libraries 2022-06-06 08:43:37 +02:00
mm zsmalloc: fix races between asynchronous zspage free and page migration 2022-06-06 08:43:39 +02:00
net NFC: NULL out the dev->rfkill to prevent UAF 2022-06-09 10:22:46 +02:00
samples x86: Prepare inline-asm for straight-line-speculation 2022-05-15 20:18:50 +02:00
scripts x86: Add straight-line-speculation mitigation 2022-05-15 20:18:51 +02:00
security lockdown: also lock down previous kgdb use 2022-05-25 09:57:37 +02:00
sound ASoC: mediatek: Fix missing of_node_put in mt2701_wm8960_machine_probe 2022-06-09 10:22:45 +02:00
tools libbpf: Don't error out on CO-RE relos for overriden weak subprogs 2022-06-09 10:22:46 +02:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt KVM: avoid NULL pointer dereference in kvm_dirty_ring_push 2022-04-13 20:59:26 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +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: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
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 MAINTAINERS: add git tree for random.c 2022-05-30 09:28:59 +02:00
Makefile Linux 5.15.45 2022-06-06 08:43:42 +02:00
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.