kernel/linux.git/include/linux/delayacct.h, branch v6.19.11

delayacct: add delay min to record delay peak

2025-01-13T04:21:16+00:00

Delay accounting can now calculate the average delay of processes, detect the overall system load, and also record the 'delay max' to identify potential abnormal delays. However, 'delay min' can help us identify another useful delay peak. By comparing the difference between 'delay max' and 'delay min', we can understand the optimization space for latency, providing a reference for the optimization of latency performance. Use case ========= bash-4.4# ./getdelays -d -t 242 print delayacct stats ON TGID 242 CPU count real total virtual total delay total delay average delay max delay min 39 156000000 156576579 2111069 0.054ms 0.212296ms 0.031307ms IO count delay total delay average delay max delay min 0 0 0.000ms 0.000000ms 0.000000ms SWAP count delay total delay average delay max delay min 0 0 0.000ms 0.000000ms 0.000000ms RECLAIM count delay total delay average delay max delay min 0 0 0.000ms 0.000000ms 0.000000ms THRASHING count delay total delay average delay max delay min 0 0 0.000ms 0.000000ms 0.000000ms COMPACT count delay total delay average delay max delay min 0 0 0.000ms 0.000000ms 0.000000ms WPCOPY count delay total delay average delay max delay min 156 11215873 0.072ms 0.207403ms 0.033913ms IRQ count delay total delay average delay max delay min 0 0 0.000ms 0.000000ms 0.000000ms Link: https://lkml.kernel.org/r/20241220173105906EOdsPhzjMLYNJJBqgz1ga@zte.com.cn Co-developed-by: Wang Yong Signed-off-by: Wang Yong Co-developed-by: xu xin Signed-off-by: xu xin Signed-off-by: Wang Yaxin Co-developed-by: Kun Jiang Signed-off-by: Kun Jiang Cc: Balbir Singh Cc: David Hildenbrand Cc: Fan Yu Cc: Peilin He Cc: tuqiang Cc: ye xingchen Cc: Yunkai Zhang Signed-off-by: Andrew Morton

delayacct: add delay max to record delay peak

2025-01-13T04:20:59+00:00

Introduce the use cases of delay max, which can help quickly detect potential abnormal delays in the system and record the types and specific details of delay spikes. Problem ======== Delay accounting can track the average delay of processes to show system workload. However, when a process experiences a significant delay, maybe a delay spike, which adversely affects performance, getdelays can only display the average system delay over a period of time. Yet, average delay is unhelpful for diagnosing delay peak. It is not even possible to determine which type of delay has spiked, as this information might be masked by the average delay. Solution ========= the 'delay max' can display delay peak since the system's startup, which can record potential abnormal delays over time, including the type of delay and the maximum delay. This is helpful for quickly identifying crash caused by delay. Use case ========= bash# ./getdelays -d -p 244 print delayacct stats ON PID 244 CPU count real total virtual total delay total delay average delay max 68 192000000 213676651 705643 0.010ms 0.306381ms IO count delay total delay average delay max 0 0 0.000ms 0.000000ms SWAP count delay total delay average delay max 0 0 0.000ms 0.000000ms RECLAIM count delay total delay average delay max 0 0 0.000ms 0.000000ms THRASHING count delay total delay average delay max 0 0 0.000ms 0.000000ms COMPACT count delay total delay average delay max 0 0 0.000ms 0.000000ms WPCOPY count delay total delay average delay max 235 15648284 0.067ms 0.263842ms IRQ count delay total delay average delay max 0 0 0.000ms 0.000000ms [wang.yaxin@zte.com.cn: update docs and fix some spelling errors] Link: https://lkml.kernel.org/r/20241213192700771XKZ8H30OtHSeziGqRVMs0@zte.com.cn Link: https://lkml.kernel.org/r/20241203164848805CS62CQPQWG9GLdQj2_BxS@zte.com.cn Co-developed-by: Wang Yong Signed-off-by: Wang Yong Co-developed-by: xu xin Signed-off-by: xu xin Co-developed-by: Wang Yaxin Signed-off-by: Wang Yaxin Signed-off-by: Kun Jiang Cc: Balbir Singh Cc: David Hildenbrand Cc: Fan Yu Cc: Peilin He Cc: tuqiang Cc: Yang Yang Cc: ye xingchen Cc: Yunkai Zhang Signed-off-by: Andrew Morton

delayacct: track delays from IRQ/SOFTIRQ

2023-04-18T23:39:34+00:00

Delay accounting does not track the delay of IRQ/SOFTIRQ. While IRQ/SOFTIRQ could have obvious impact on some workloads productivity, such as when workloads are running on system which is busy handling network IRQ/SOFTIRQ. Get the delay of IRQ/SOFTIRQ could help users to reduce such delay. Such as setting interrupt affinity or task affinity, using kernel thread for NAPI etc. This is inspired by "sched/psi: Add PSI_IRQ to track IRQ/SOFTIRQ pressure"[1]. Also fix some code indent problems of older code. And update tools/accounting/getdelays.c: / # ./getdelays -p 156 -di print delayacct stats ON printing IO accounting PID 156 CPU count real total virtual total delay total delay average 15 15836008 16218149 275700790 18.380ms IO count delay total delay average 0 0 0.000ms SWAP count delay total delay average 0 0 0.000ms RECLAIM count delay total delay average 0 0 0.000ms THRASHING count delay total delay average 0 0 0.000ms COMPACT count delay total delay average 0 0 0.000ms WPCOPY count delay total delay average 36 7586118 0.211ms IRQ count delay total delay average 42 929161 0.022ms [1] commit 52b1364ba0b1("sched/psi: Add PSI_IRQ to track IRQ/SOFTIRQ pressure") Link: https://lkml.kernel.org/r/202304081728353557233@zte.com.cn Signed-off-by: Yang Yang Cc: Jiang Xuexin Cc: wangyong Cc: junhua huang Cc: Balbir Singh Cc: Ingo Molnar Cc: Jonathan Corbet Cc: Juri Lelli Cc: Peter Zijlstra Signed-off-by: Andrew Morton

delayacct: support re-entrance detection of thrashing accounting

2022-09-27T02:46:07+00:00

Once upon a time, we only support accounting thrashing of page cache. Then Joonsoo introduced workingset detection for anonymous pages and we gained the ability to account thrashing of them[1]. For page cache thrashing accounting, there is no suitable place to do it in fs level likes swap_readpage(). So we have to do it in folio_wait_bit_common(). Then for anonymous pages thrashing accounting, we have to do it in both swap_readpage() and folio_wait_bit_common(). This likes PSI, so we should let thrashing accounting supports re-entrance detection. This patch is to prepare complete thrashing accounting, and is based on patch "filemap: make the accounting of thrashing more consistent". [1] commit aae466b0052e ("mm/swap: implement workingset detection for anonymous LRU") Link: https://lkml.kernel.org/r/20220815071134.74551-1-yang.yang29@zte.com.cn Signed-off-by: Yang Yang Signed-off-by: CGEL ZTE Reviewed-by: Ran Xiaokai Reviewed-by: wangyong Acked-by: Joonsoo Kim Signed-off-by: Andrew Morton

delayacct: track delays from write-protect copy

2022-06-01T22:55:25+00:00

Delay accounting does not track the delay of write-protect copy. When tasks trigger many write-protect copys(include COW and unsharing of anonymous pages[1]), it may spend a amount of time waiting for them. To get the delay of tasks in write-protect copy, could help users to evaluate the impact of using KSM or fork() or GUP. Also update tools/accounting/getdelays.c: / # ./getdelays -dl -p 231 print delayacct stats ON listen forever PID 231 CPU count real total virtual total delay total delay average 6247 1859000000 2154070021 1674255063 0.268ms IO count delay total delay average 0 0 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 0 0 0ms COMPACT count delay total delay average 3 72758 0ms WPCOPY count delay total delay average 3635 271567604 0ms [1] commit 31cc5bc4af70("mm: support GUP-triggered unsharing of anonymous pages") Link: https://lkml.kernel.org/r/20220409014342.2505532-1-yang.yang29@zte.com.cn Signed-off-by: Yang Yang Reviewed-by: David Hildenbrand Reviewed-by: Jiang Xuexin Reviewed-by: Ran Xiaokai Reviewed-by: wangyong Cc: Jonathan Corbet Cc: Balbir Singh Cc: Mike Kravetz Cc: Stephen Rothwell Signed-off-by: Andrew Morton

kernel/delayacct: move delayacct sysctls to its own file

2022-04-06T20:43:44+00:00

kernel/sysctl.c is a kitchen sink where everyone leaves their dirty dishes, this makes it very difficult to maintain. To help with this maintenance let's start by moving sysctls to places where they actually belong. The proc sysctl maintainers do not want to know what sysctl knobs you wish to add for your own piece of code, we just care about the core logic. All filesystem syctls now get reviewed by fs folks. This commit follows the commit of fs, move the delayacct sysctl to its own file, kernel/delayacct.c. Signed-off-by: tangmeng Signed-off-by: Luis Chamberlain

delayacct: track delays from memory compact

2022-01-20T06:52:55+00:00

Delay accounting does not track the delay of memory compact. When there is not enough free memory, tasks can spend a amount of their time waiting for compact. To get the impact of tasks in direct memory compact, measure the delay when allocating memory through memory compact. Also update tools/accounting/getdelays.c: / # ./getdelays_next -di -p 304 print delayacct stats ON printing IO accounting PID 304 CPU count real total virtual total delay total delay average 277 780000000 849039485 18877296 0.068ms IO count delay total delay average 0 0 0ms SWAP count delay total delay average 0 0 0ms RECLAIM count delay total delay average 5 11088812685 2217ms THRASHING count delay total delay average 0 0 0ms COMPACT count delay total delay average 3 72758 0ms watch: read=0, write=0, cancelled_write=0 Link: https://lkml.kernel.org/r/1638619795-71451-1-git-send-email-wang.yong12@zte.com.cn Signed-off-by: wangyong Reviewed-by: Jiang Xuexin Reviewed-by: Zhang Wenya Reviewed-by: Yang Yang Reviewed-by: Balbir Singh Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

delayacct: cleanup flags in struct task_delay_info and functions use it

2022-01-20T06:52:55+00:00

Flags in struct task_delay_info is used to distinguish the difference between swapin and blkio delay acountings. But after patch "delayacct: support swapin delay accounting for swapping without blkio", there is no need to do that since swapin and blkio delay accounting use their own functions. Link: https://lkml.kernel.org/r/20211124065958.36703-1-yang.yang29@zte.com.cn Signed-off-by: Yang Yang Cc: Balbir Singh Cc: Ingo Molnar Cc: Johannes Weiner Cc: Peter Zijlstra Cc: Zeal Robot Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

delayacct: fix incomplete disable operation when switch enable to disable

2022-01-20T06:52:55+00:00

When a task is created after delayacct is enabled, kernel will do all the delay accountings for that task. The problems is if user disables delayacct by set /proc/sys/kernel/task_delayacct to zero, only blkio delay accounting is disabled. Now disable all the kinds of delay accountings when /proc/sys/kernel/task_delayacct sets to zero. Link: https://lkml.kernel.org/r/20211123140342.32962-1-ran.xiaokai@zte.com.cn Signed-off-by: Yang Yang Reported-by: Zeal Robot Cc: Balbir Singh Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Johannes Weiner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

delayacct: support swapin delay accounting for swapping without blkio

2022-01-20T06:52:55+00:00

Currently delayacct accounts swapin delay only for swapping that cause blkio. If we use zram for swapping, tools/accounting/getdelays can't get any SWAP delay. It's useful to get zram swapin delay information, for example to adjust compress algorithm or /proc/sys/vm/swappiness. Reference to PSI, it accounts any kind of swapping by doing its work in swap_readpage(), no matter whether swapping causes blkio. Let delayacct do the similar work. Link: https://lkml.kernel.org/r/20211112083813.8559-1-yang.yang29@zte.com.cn Signed-off-by: Yang Yang Reported-by: Zeal Robot Cc: Balbir Singh Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Johannes Weiner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds