user/sven/linux.git/kernel/delayacct.c, branch v5.15.34

delayacct: Add sysctl to enable at runtime

2021-05-12T09:43:25Z

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

2021-05-12T09:43:25Z

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

delayacct: Add static_branch in scheduler hooks

2021-05-12T09:43:25Z

Cheaper when delayacct is disabled. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Thomas Gleixner Reviewed-by: Ingo Molnar Acked-by: Balbir Singh Acked-by: Johannes Weiner Link: https://lkml.kernel.org/r/20210505111525.248028369@infradead.org

sched: Simplify sched_info_on()

2021-05-12T09:43:24Z

The situation around sched_info is somewhat complicated, it is used by sched_stats and delayacct and, indirectly, kvm. If SCHEDSTATS=Y (but disabled by default) sched_info_on() is unconditionally true -- this is the case for all distro kernel configs I checked. If for some reason SCHEDSTATS=N, but TASK_DELAY_ACCT=Y, then sched_info_on() can return false when delayacct is disabled, presumably because there would be no other users left; except kvm is. Instead of complicating matters further by accurately accounting sched_stat and kvm state, simply unconditionally enable when SCHED_INFO=Y, matching the common distro case. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Thomas Gleixner Reviewed-by: Ingo Molnar Acked-by: Johannes Weiner Link: https://lkml.kernel.org/r/20210505111525.121458839@infradead.org

delayacct: Use sched_clock()

2021-05-12T09:43:23Z

Like all scheduler statistics, use sched_clock() based time. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Rik van Riel Reviewed-by: Thomas Gleixner Reviewed-by: Ingo Molnar Acked-by: Johannes Weiner Acked-by: Balbir Singh Link: https://lkml.kernel.org/r/20210505111525.001031466@infradead.org

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 25

2019-05-21T09:52:39Z

Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation either version 2 of the license or at your option any later version this program is distributed in the hope that it would be useful but without any warranty without even the implied warranty of merchantability or fitness for a particular purpose see the gnu general public license for more details extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 6 file(s). Signed-off-by: Thomas Gleixner Reviewed-by: Steve Winslow Reviewed-by: Kate Stewart Reviewed-by: Jilayne Lovejoy Reviewed-by: Allison Randal Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190519154043.007767574@linutronix.de Signed-off-by: Greg Kroah-Hartman

delayacct: track delays from thrashing cache pages

2018-10-26T23:26:32Z

Delay accounting already measures the time a task spends in direct reclaim and waiting for swapin, but in low memory situations tasks spend can spend a significant amount of their time waiting on thrashing page cache. This isn't tracked right now. To know the full impact of memory contention on an individual task, measure the delay when waiting for a recently evicted active cache page to read back into memory. Also update tools/accounting/getdelays.c: [hannes@computer accounting]$ sudo ./getdelays -d -p 1 print delayacct stats ON PID 1 CPU count real total virtual total delay total delay average 50318 745000000 847346785 400533713 0.008ms IO count delay total delay average 435 122601218 0ms SWAP count delay total delay average 0 0 0ms RECLAIM count delay total delay average 0 0 0ms THRASHING count delay total delay average 19 12621439 0ms Link: http://lkml.kernel.org/r/20180828172258.3185-4-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Acked-by: Peter Zijlstra (Intel) Tested-by: Daniel Drake Tested-by: Suren Baghdasaryan Cc: Christopher Lameter Cc: Ingo Molnar Cc: Johannes Weiner Cc: Mike Galbraith Cc: Peter Enderborg Cc: Randy Dunlap Cc: Shakeel Butt Cc: Tejun Heo Cc: Vinayak Menon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

delayacct: Use raw_spinlocks

2018-04-27T12:34:51Z

try_to_wake_up() might invoke delayacct_blkio_end() while holding the pi_lock (which is a raw_spinlock_t). delayacct_blkio_end() acquires task_delay_info.lock which is a spinlock_t. This causes a might sleep splat on -RT where non raw spinlocks are converted to 'sleeping' spinlocks. task_delay_info.lock is only held for a short amount of time so it's not a problem latency wise to make convert it to a raw spinlock. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Cc: Balbir Singh Link: https://lkml.kernel.org/r/20180423161024.6710-1-bigeasy@linutronix.de

delayacct: Account blkio completion on the correct task

2018-01-16T02:29:36Z

Before commit: e33a9bba85a8 ("sched/core: move IO scheduling accounting from io_schedule_timeout() into scheduler") delayacct_blkio_end() was called after context-switching into the task which completed I/O. This resulted in double counting: the task would account a delay both waiting for I/O and for time spent in the runqueue. With e33a9bba85a8, delayacct_blkio_end() is called by try_to_wake_up(). In ttwu, we have not yet context-switched. This is more correct, in that the delay accounting ends when the I/O is complete. But delayacct_blkio_end() relies on 'get_current()', and we have not yet context-switched into the task whose I/O completed. This results in the wrong task having its delay accounting statistics updated. Instead of doing that, pass the task_struct being woken to delayacct_blkio_end(), so that it can update the statistics of the correct task. Signed-off-by: Josh Snyder Acked-by: Tejun Heo Acked-by: Balbir Singh Cc: Cc: Brendan Gregg Cc: Jens Axboe Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-block@vger.kernel.org Fixes: e33a9bba85a8 ("sched/core: move IO scheduling accounting from io_schedule_timeout() into scheduler") Link: http://lkml.kernel.org/r/1513613712-571-1-git-send-email-joshs@netflix.com Signed-off-by: Ingo Molnar

sched/headers: Prepare to move cputime functionality from into

2017-03-02T07:42:39Z

Introduce a trivial, mostly empty header to prepare for the moving of cputime functionality out of sched.h. Update all code that relies on these facilities. Acked-by: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar