kernel/linux.git/Documentation/accounting, branch master

delayacct: add timestamp of delay max

2026-02-01T00:16:06+00:00

Problem ======= Commit 658eb5ab916d ("delayacct: add delay max to record delay peak") introduced the delay max for getdelays, which records abnormal latency peaks and helps us understand the magnitude of such delays. However, the peak latency value alone is insufficient for effective root cause analysis. Without the precise timestamp of when the peak occurred, we still lack the critical context needed to correlate it with other system events. Solution ======== To address this, we need to additionally record a precise timestamp when the maximum latency occurs. By correlating this timestamp with system logs and monitoring metrics, we can identify processes with abnormal resource usage at the same moment, which can help us to pinpoint root causes. Use Case ======== bash-4.4# ./getdelays -d -t 227 print delayacct stats ON TGID 227 CPU count real total virtual total delay total delay average delay max delay min delay max timestamp 46 188000000 192348334 4098012 0.089ms 0.429260ms 0.051205ms 2026-01-15T15:06:58 IO count delay total delay average delay max delay min delay max timestamp 0 0 0.000ms 0.000000ms 0.000000ms N/A SWAP count delay total delay average delay max delay min delay max timestamp 0 0 0.000ms 0.000000ms 0.000000ms N/A RECLAIM count delay total delay average delay max delay min delay max timestamp 0 0 0.000ms 0.000000ms 0.000000ms N/A THRAS HING count delay total delay average delay max delay min delay max timestamp 0 0 0.000ms 0.000000ms 0.000000ms N/A COMPACT count delay total delay average delay max delay min delay max timestamp 0 0 0.000ms 0.000000ms 0.000000ms N/A WPCOPY count delay total delay average delay max delay min delay max timestamp 182 19413338 0.107ms 0.547353ms 0.022462ms 2026-01-15T15:05:24 IRQ count delay total delay average delay max delay min delay max timestamp 0 0 0.000ms 0.000000ms 0.000000ms N/A Link: https://lkml.kernel.org/r/20260119100241520gWubW8-5QfhSf9gjqcc_E@zte.com.cn Signed-off-by: Wang Yaxin Cc: Fan Yu Cc: Jonathan Corbet Cc: xu xin Cc: Yang Yang Signed-off-by: Andrew Morton

Documentation: taskstats: Reindent payload kinds list

2025-11-10T19:52:12+00:00

Payload kinds list text is indented at the first text column, rather than aligned to the list number. As an effect, the third item becomes sublist of second item's third sublist item (TASKTYPE_TYPE_STATS). Reindent the list text. Signed-off-by: Bagas Sanjaya Reviewed-by: Randy Dunlap Tested-by: Randy Dunlap Signed-off-by: Jonathan Corbet Message-ID: <20251104130751.22755-1-bagasdotme@gmail.com>

docs: update delaytop documentation for new interactive features

2025-09-14T00:32:56+00:00

This commit updates the delaytop documentation to reflect the newly added features: 1) Added comprehensive description of interactive keyboard controls 2) Documented all available sort fields 3) Added examples for advanced usage scenarios 4) Included PSI availability note Link: https://lkml.kernel.org/r/20250907001457696qAqUGGkV1VfEO6OkVMovW@zte.com.cn Signed-off-by: Fan Yu Reviewed-by: xu xin Signed-off-by: Andrew Morton

delaytop: enhance error logging and add PSI feature description

2025-08-02T19:01:41+00:00

This patch improves error diagnostics and documentation for delaytop: 1) Enhanced error logging: - Added explicit error messages in critical failure paths - Implemented BOOL_FPRINT macro for robust output handling 2) PSI feature documentation: - Updated header comment to reflect PSI monitoring capability - Improved output formatting for PSI information System Pressure Information: (avg10/avg60/avg300/total) CPU some: 0.0%/ 0.0%/ 0.0%/ 345(ms) CPU full: 0.0%/ 0.0%/ 0.0%/ 0(ms) Memory full: 0.0%/ 0.0%/ 0.0%/ 0(ms) Memory some: 0.0%/ 0.0%/ 0.0%/ 0(ms) IO full: 0.0%/ 0.0%/ 0.0%/ 65(ms) IO some: 0.0%/ 0.0%/ 0.0%/ 79(ms) IRQ full: 0.0%/ 0.0%/ 0.0%/ 0(ms) Link: https://lkml.kernel.org/r/202507281628341752gMXCMN7S-Vz_LHYHum9r@zte.com.cn Signed-off-by: Fan Yu Signed-off-by: Wang Yaxin Acked-by: Yang Yang Cc: Fan Yu Cc: Jonathan Corbet Cc: xu xin Signed-off-by: Andrew Morton

docs: update docs after introducing delaytop

2025-07-20T02:08:29+00:00

The "getdelays" can only display the latency of a single task by specifying a PID, we introduce the "delaytop" with the following capabilities: 1. system view: monitors latency metrics (CPU, I/O, memory, IRQ, etc.) for all system processes 2. supports field-based sorting (e.g., default sort by CPU latency in descending order) 3. dynamic interactive interface: focus on specific processes with --pid; limit displayed entries with --processes 20; control monitoring duration with --iterations; Link: https://lkml.kernel.org/r/2025071013514177028RdjISjqeIOnTCRvGAwy@zte.com.cn Signed-off-by: Fan Yu Signed-off-by: Wang Yaxin Signed-off-by: Jiang Kun Cc: Balbir Singh Cc: David Hildenbrand Cc: Peilin He Cc: Qiang Tu Cc: wangyong Cc: xu xin Cc: Yang Yang Cc: Yunkai Zhang Signed-off-by: Andrew Morton

Merge tag 'mm-nonmm-stable-2025-01-24-23-16' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2025-01-27T01:50:53+00:00

Pull non-MM updates from Andrew Morton: "Mainly individually changelogged singleton patches. The patch series in this pull are: - "lib min_heap: Improve min_heap safety, testing, and documentation" from Kuan-Wei Chiu provides various tightenings to the min_heap library code - "xarray: extract __xa_cmpxchg_raw" from Tamir Duberstein preforms some cleanup and Rust preparation in the xarray library code - "Update reference to include/asm-" from Geert Uytterhoeven fixes pathnames in some code comments - "Converge on using secs_to_jiffies()" from Easwar Hariharan uses the new secs_to_jiffies() in various places where that is appropriate - "ocfs2, dlmfs: convert to the new mount API" from Eric Sandeen switches two filesystems to the new mount API - "Convert ocfs2 to use folios" from Matthew Wilcox does that - "Remove get_task_comm() and print task comm directly" from Yafang Shao removes now-unneeded calls to get_task_comm() in various places - "squashfs: reduce memory usage and update docs" from Phillip Lougher implements some memory savings in squashfs and performs some maintainability work - "lib: clarify comparison function requirements" from Kuan-Wei Chiu tightens the sort code's behaviour and adds some maintenance work - "nilfs2: protect busy buffer heads from being force-cleared" from Ryusuke Konishi fixes an issues in nlifs when the fs is presented with a corrupted image - "nilfs2: fix kernel-doc comments for function return values" from Ryusuke Konishi fixes some nilfs kerneldoc - "nilfs2: fix issues with rename operations" from Ryusuke Konishi addresses some nilfs BUG_ONs which syzbot was able to trigger - "minmax.h: Cleanups and minor optimisations" from David Laight does some maintenance work on the min/max library code - "Fixes and cleanups to xarray" from Kemeng Shi does maintenance work on the xarray library code" * tag 'mm-nonmm-stable-2025-01-24-23-16' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (131 commits) ocfs2: use str_yes_no() and str_no_yes() helper functions include/linux/lz4.h: add some missing macros Xarray: use xa_mark_t in xas_squash_marks() to keep code consistent Xarray: remove repeat check in xas_squash_marks() Xarray: distinguish large entries correctly in xas_split_alloc() Xarray: move forward index correctly in xas_pause() Xarray: do not return sibling entries from xas_find_marked() ipc/util.c: complete the kernel-doc function descriptions gcov: clang: use correct function param names latencytop: use correct kernel-doc format for func params minmax.h: remove some #defines that are only expanded once minmax.h: simplify the variants of clamp() minmax.h: move all the clamp() definitions after the min/max() ones minmax.h: use BUILD_BUG_ON_MSG() for the lo < hi test in clamp() minmax.h: reduce the #define expansion of min(), max() and clamp() minmax.h: update some comments minmax.h: add whitespace around operators and after commas nilfs2: do not update mtime of renamed directory that is not moved nilfs2: handle errors that nilfs_prepare_chunk() may return CREDITS: fix spelling mistake ...

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

Documentation/accounting: Fix typo in taskstats-struct.rst

2024-12-13T15:44:29+00:00

Corrected a typo in the 'taskstats-struct.rst' documentation. The macro name 'TAKSTATS_VERSION' was mistakenly mentioned instead of the correct 'TASKSTATS_VERSION'. The corrected line now references the proper macro 'TASKSTATS_VERSION', defined in ''. Signed-off-by: Sarveshwaar SS Signed-off-by: Jonathan Corbet Link: https://lore.kernel.org/r/20241208083320.16190-1-sarvesh20123@gmail.com

docs: psi: use correct config name

2023-07-31T15:54:17+00:00

Commit 2ce7135adc9a ("psi: cgroup support") adds documentation which refers to CONFIG_CGROUP, but the correct name is CONFIG_CGROUPS. Correct the reference to CONFIG_CGROUPS. Co-developed-by: Sabina Trendota Signed-off-by: Sabina Trendota Signed-off-by: Ramazan Safiullin Signed-off-by: Jonathan Corbet Link: https://lore.kernel.org/r/20230728115600.231068-1-ram.safiullin2001@gmail.com