kernel/linux.git/Documentation/accounting, branch v5.15.208

sched/psi: report zeroes for CPU full at the system level

2022-06-09T08:22:48+00:00

[ Upstream commit 890d550d7dbac7a31ecaa78732aa22be282bb6b8 ] 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 e7fcd7622823 ("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: e7fcd7622823 ("psi: Add PSI_CPU_FULL state") Reported-by: Martin Steigerwald Suggested-by: Johannes Weiner Signed-off-by: Chengming Zhou Signed-off-by: Peter Zijlstra (Intel) Acked-by: Johannes Weiner Link: https://lore.kernel.org/r/20220408121914.82855-1-zhouchengming@bytedance.com Signed-off-by: Sasha Levin

psi: Fix uaf issue when psi trigger is destroyed while being polled

2022-02-01T16:27:01+00:00

commit a06247c6804f1a7c86a2e5398a4c1f1db1471848 upstream. With write operation on psi files replacing old trigger with a new one, the lifetime of its waitqueue is totally arbitrary. Overwriting an existing trigger causes its waitqueue to be freed and pending poll() will stumble on trigger->event_wait which was destroyed. Fix this by disallowing to redefine an existing psi trigger. If a write operation is used on a file descriptor with an already existing psi trigger, the operation will fail with EBUSY error. Also bypass a check for psi_disabled in the psi_trigger_destroy as the flag can be flipped after the trigger is created, leading to a memory leak. Fixes: 0e94682b73bf ("psi: introduce psi monitor") Reported-by: syzbot+cdb5dd11c97cc532efad@syzkaller.appspotmail.com Suggested-by: Linus Torvalds Analyzed-by: Eric Biggers Signed-off-by: Suren Baghdasaryan Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Eric Biggers Acked-by: Johannes Weiner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20220111232309.1786347-1-surenb@google.com Signed-off-by: Greg Kroah-Hartman

delayacct: Add sysctl to enable at runtime

2021-05-12T09:43:25+00:00

Just like sched_schedstats, allow runtime enabling (and disabling) of delayacct. This is useful if one forgot to add the delayacct boot time option. Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/YJkhebGJAywaZowX@hirez.programming.kicks-ass.net

delayacct: Default disabled

2021-05-12T09:43:25+00:00

Assuming this stuff isn't actually used much; disable it by default and avoid allocating and tracking the task_delay_info structure. taskstats is changed to still report the regular sched and sched_info and only skip the missing task_delay_info fields instead of not reporting anything. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Thomas Gleixner Reviewed-by: Ingo Molnar Link: https://lkml.kernel.org/r/20210505111525.308018373@infradead.org

Documentation: Replace lkml.org links with lore

2021-01-11T19:47:38+00:00

Replace the lkml.org links with lore to better use a single source that's more likely to stay available long-term. Done by bash script: cvt_lkml_to_lore () { tmpfile=$(mktemp ./.cvt_links.XXXXXXX) header=$(echo $1 | sed 's@/lkml/@/lkml/headers/@') wget -qO - $header > $tmpfile if [[ $? == 0 ]] ; then link=$(grep -i '^Message-Id:' $tmpfile | head -1 | \ sed -r -e 's/^\s*Message-Id:\s*<\s*//' -e 's/\s*>\s*$//' -e 's@^@https://lore.kernel.org/r/@') # echo "testlink: $link" if [ -n "$link" ] ; then wget -qO - $link > /dev/null if [[ $? == 0 ]] ; then echo $link fi fi fi rm -f $tmpfile } git grep -P -o "\bhttps?://(?:www.)?lkml.org/lkml[\/\w]+" $@ | while read line ; do echo $line file=$(echo $line | cut -f1 -d':') link=$(echo $line | cut -f2- -d':') newlink=$(cvt_lkml_to_lore $link) if [[ -n "$newlink" ]] ; then sed -i -e "s#\b$link\b#$newlink#" $file fi done Link: https://lore.kernel.org/patchwork/patch/1265849/#1462688 Signed-off-by: Joe Perches Link: https://lore.kernel.org/r/77cdb7f32cfb087955bfc3600b86c40bed5d4104.camel@perches.com Signed-off-by: Jonathan Corbet

doc: cgroup: improve formatting of references

2020-03-02T19:57:03+00:00

Annotate references to other documents to make them clickable. Signed-off-by: Jakub Kicinski Acked-by: Johannes Weiner Link: https://lore.kernel.org/r/20200228000653.1572553-6-kuba@kernel.org Signed-off-by: Jonathan Corbet

docs: add some documentation dirs to the driver-api book

2019-07-15T14:03:02+00:00

Those are subsystem docs, with a mix of kABI and user-faced docs. While they're not split, keep the dirs where they are, adding just a pointer to the main index. Signed-off-by: Mauro Carvalho Chehab

docs: accounting: convert to ReST

2019-07-15T12:20:25+00:00

Rename the accounting documentation files to ReST, add an index for them and adjust in order to produce a nice html output via the Sphinx build system. At its new index.rst, let's add a :orphan: while this is not linked to the main index.rst file, in order to avoid build warnings. Signed-off-by: Mauro Carvalho Chehab

psi: introduce psi monitor

2019-05-15T02:52:48+00:00

Psi monitor aims to provide a low-latency short-term pressure detection mechanism configurable by users. It allows users to monitor psi metrics growth and trigger events whenever a metric raises above user-defined threshold within user-defined time window. Time window and threshold are both expressed in usecs. Multiple psi resources with different thresholds and window sizes can be monitored concurrently. Psi monitors activate when system enters stall state for the monitored psi metric and deactivate upon exit from the stall state. While system is in the stall state psi signal growth is monitored at a rate of 10 times per tracking window. Min window size is 500ms, therefore the min monitoring interval is 50ms. Max window size is 10s with monitoring interval of 1s. When activated psi monitor stays active for at least the duration of one tracking window to avoid repeated activations/deactivations when psi signal is bouncing. Notifications to the users are rate-limited to one per tracking window. Link: http://lkml.kernel.org/r/20190319235619.260832-8-surenb@google.com Signed-off-by: Suren Baghdasaryan Signed-off-by: Johannes Weiner Cc: Dennis Zhou Cc: Ingo Molnar Cc: Jens Axboe Cc: Li Zefan Cc: Peter Zijlstra Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

psi: clarify the units used in pressure files

2019-04-06T02:02:31+00:00

The output of the PSI files show a bunch of numbers with no unit. The psi.txt documentation file also does not indicate what units are used. One can only find out by looking at the source code. The units are percentage for the averages and useconds for the total. Make the information easier to find by documenting the units in psi.txt. Link: http://lkml.kernel.org/r/20190402193810.3450-1-longman@redhat.com Signed-off-by: Waiman Long Acked-by: Johannes Weiner Cc: "Peter Zijlstra (Intel)" Cc: Tejun Heo Cc: Jonathan Corbet Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds