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docs: update docs after introducing delaytop

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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 <fan.yu9@zte.com.cn>
Signed-off-by: Wang Yaxin <wang.yaxin@zte.com.cn>
Signed-off-by: Jiang Kun <jiang.kun2@zte.com.cn>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Peilin He <he.peilin@zte.com.cn>
Cc: Qiang Tu <tu.qiang35@zte.com.cn>
Cc: wangyong <wang.yong12@zte.com.cn>
Cc: xu xin <xu.xin16@zte.com.cn>
Cc: Yang Yang <yang.yang29@zte.com.cn>
Cc: Yunkai Zhang <zhang.yunkai@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Wang Yaxin 2025-07-10 13:51:41 +08:00 committed by Andrew Morton
parent 6b47c9f8ee
commit 320bf1709a
1 changed files with 47 additions and 0 deletions
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47
Documentation/accounting/delay-accounting.rst
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@ -131,3 +131,50 @@ Get IO accounting for pid 1, it works only with -p::
linuxrc: read=65536, write=0, cancelled_write=0
The above command can be used with -v to get more debug information.
After the system starts, use `delaytop` to get the Top-N high-latency tasks.
this tool supports sorting by CPU latency in descending order by default,
displays the top 20 high-latency tasks by default, and refreshes the latency
data every 2 seconds by default.
Get Top-N tasks delay, since system boot::
bash# ./delaytop
Top 20 processes (sorted by CPU delay):
PID TGID COMMAND CPU(ms) IO(ms) SWAP(ms) RCL(ms) THR(ms) CMP(ms) WP(ms) IRQ(ms)
---------------------------------------------------------------------------------------------
32 32 kworker/2:0H-sy 23.65 0.00 0.00 0.00 0.00 0.00 0.00 0.00
497 497 kworker/R-scsi_ 1.20 0.00 0.00 0.00 0.00 0.00 0.00 0.00
495 495 kworker/R-scsi_ 1.13 0.00 0.00 0.00 0.00 0.00 0.00 0.00
494 494 scsi_eh_0 1.12 0.00 0.00 0.00 0.00 0.00 0.00 0.00
485 485 kworker/R-ata_s 0.90 0.00 0.00 0.00 0.00 0.00 0.00 0.00
574 574 kworker/R-kdmfl 0.36 0.00 0.00 0.00 0.00 0.00 0.00 0.00
34 34 idle_inject/3 0.33 0.00 0.00 0.00 0.00 0.00 0.00 0.00
1123 1123 nde-netfilter 0.28 0.00 0.00 0.00 0.00 0.00 0.00 0.00
60 60 ksoftirqd/7 0.25 0.00 0.00 0.00 0.00 0.00 0.00 0.00
114 114 kworker/0:2-cgr 0.25 0.00 0.00 0.00 0.00 0.00 0.00 0.00
496 496 scsi_eh_1 0.24 0.00 0.00 0.00 0.00 0.00 0.00 0.00
51 51 cpuhp/6 0.24 0.00 0.00 0.00 0.00 0.00 0.00 0.00
1667 1667 atd 0.24 0.00 0.00 0.00 0.00 0.00 0.00 0.00
45 45 cpuhp/5 0.23 0.00 0.00 0.00 0.00 0.00 0.00 0.00
1102 1102 nde-backupservi 0.22 0.00 0.00 0.00 0.00 0.00 0.00 0.00
1098 1098 systemsettings 0.21 0.00 0.00 0.00 0.00 0.00 0.00 0.00
1100 1100 audit-monitor 0.20 0.00 0.00 0.00 0.00 0.00 0.00 0.00
53 53 migration/6 0.20 0.00 0.00 0.00 0.00 0.00 0.00 0.00
1482 1482 sshd 0.19 0.00 0.00 0.00 0.00 0.00 0.00 0.00
39 39 cpuhp/4 0.19 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Dynamic interactive interface of delaytop::
# ./delaytop -p pid
Print delayacct stats
# ./delaytop -P num
Display the top N tasks
# ./delaytop -n num
Set delaytop refresh frequency (num times)
# ./delaytop -d secs
Specify refresh interval as secs