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docs: update delaytop documentation for new interactive features
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 <fan.yu9@zte.com.cn>
Reviewed-by: xu xin <xu.xin16@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
authored by
Fan Yu
and committed by
Andrew Morton
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Documentation/accounting/delay-accounting.rst
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Documentation/accounting/delay-accounting.rst
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After the system starts, use `delaytop` to get the system-wide delay information,
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which includes system-wide PSI information and Top-N high-latency tasks.
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Note: PSI support requires `CONFIG_PSI=y` and `psi=1` for full functionality.
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`delaytop` supports sorting by CPU latency in descending order by default,
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displays the top 20 high-latency tasks by default, and refreshes the latency
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data every 2 seconds by default.
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`delaytop` is an interactive tool for monitoring system pressure and task delays.
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It supports multiple sorting options, display modes, and real-time keyboard controls.
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Get PSI information and Top-N tasks delay, since system boot::
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Basic usage with default settings (sorts by CPU delay, shows top 20 tasks, refreshes every 2 seconds)::
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bash# ./delaytop
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System Pressure Information: (avg10/avg60/avg300/total)
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CPU some: 0.0%/ 0.0%/ 0.0%/ 345(ms)
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System Pressure Information: (avg10/avg60vg300/total)
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CPU some: 0.0%/ 0.0%/ 0.0%/ 106137(ms)
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CPU full: 0.0%/ 0.0%/ 0.0%/ 0(ms)
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Memory full: 0.0%/ 0.0%/ 0.0%/ 0(ms)
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Memory some: 0.0%/ 0.0%/ 0.0%/ 0(ms)
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IO full: 0.0%/ 0.0%/ 0.0%/ 65(ms)
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IO some: 0.0%/ 0.0%/ 0.0%/ 79(ms)
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IO full: 0.0%/ 0.0%/ 0.0%/ 2240(ms)
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IO some: 0.0%/ 0.0%/ 0.0%/ 2783(ms)
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IRQ full: 0.0%/ 0.0%/ 0.0%/ 0(ms)
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Top 20 processes (sorted by CPU delay):
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PID TGID COMMAND CPU(ms) IO(ms) SWAP(ms) RCL(ms) THR(ms) CMP(ms) WP(ms) IRQ(ms)
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----------------------------------------------------------------------------------------------
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161 161 zombie_memcg_re 1.40 0.00 0.00 0.00 0.00 0.00 0.00 0.00
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130 130 blkcg_punt_bio 1.37 0.00 0.00 0.00 0.00 0.00 0.00 0.00
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444 444 scsi_tmf_0 0.73 0.00 0.00 0.00 0.00 0.00 0.00 0.00
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1280 1280 rsyslogd 0.53 0.04 0.00 0.00 0.00 0.00 0.00 0.00
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12 12 ksoftirqd/0 0.47 0.00 0.00 0.00 0.00 0.00 0.00 0.00
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1277 1277 nbd-server 0.44 0.00 0.00 0.00 0.00 0.00 0.00 0.00
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308 308 kworker/2:2-sys 0.41 0.00 0.00 0.00 0.00 0.00 0.00 0.00
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55 55 netns 0.36 0.00 0.00 0.00 0.00 0.00 0.00 0.00
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1187 1187 acpid 0.31 0.03 0.00 0.00 0.00 0.00 0.00 0.00
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6184 6184 kworker/1:2-sys 0.24 0.00 0.00 0.00 0.00 0.00 0.00 0.00
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186 186 kaluad 0.24 0.00 0.00 0.00 0.00 0.00 0.00 0.00
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18 18 ksoftirqd/1 0.24 0.00 0.00 0.00 0.00 0.00 0.00 0.00
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185 185 kmpath_rdacd 0.23 0.00 0.00 0.00 0.00 0.00 0.00 0.00
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190 190 kstrp 0.23 0.00 0.00 0.00 0.00 0.00 0.00 0.00
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2759 2759 agetty 0.20 0.03 0.00 0.00 0.00 0.00 0.00 0.00
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1190 1190 kworker/0:3-sys 0.19 0.00 0.00 0.00 0.00 0.00 0.00 0.00
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1272 1272 sshd 0.15 0.04 0.00 0.00 0.00 0.00 0.00 0.00
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1156 1156 license 0.15 0.11 0.00 0.00 0.00 0.00 0.00 0.00
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134 134 md 0.13 0.00 0.00 0.00 0.00 0.00 0.00 0.00
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6142 6142 kworker/3:2-xfs 0.13 0.00 0.00 0.00 0.00 0.00 0.00 0.00
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[o]sort [M]memverbose [q]quit
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Top 20 processes (sorted by cpu delay):
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PID TGID COMMAND CPU(ms) IO(ms) IRQ(ms) MEM(ms)
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------------------------------------------------------------------------
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110 110 kworker/15:0H-s 27.91 0.00 0.00 0.00
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57 57 cpuhp/7 3.18 0.00 0.00 0.00
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99 99 cpuhp/14 2.97 0.00 0.00 0.00
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51 51 cpuhp/6 0.90 0.00 0.00 0.00
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44 44 kworker/4:0H-sy 0.80 0.00 0.00 0.00
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60 60 ksoftirqd/7 0.74 0.00 0.00 0.00
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76 76 idle_inject/10 0.31 0.00 0.00 0.00
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100 100 idle_inject/14 0.30 0.00 0.00 0.00
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1309 1309 systemsettings 0.29 0.00 0.00 0.00
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45 45 cpuhp/5 0.22 0.00 0.00 0.00
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63 63 cpuhp/8 0.20 0.00 0.00 0.00
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87 87 cpuhp/12 0.18 0.00 0.00 0.00
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93 93 cpuhp/13 0.17 0.00 0.00 0.00
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1265 1265 acpid 0.17 0.00 0.00 0.00
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1552 1552 sshd 0.17 0.00 0.00 0.00
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2584 2584 sddm-helper 0.16 0.00 0.00 0.00
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1284 1284 rtkit-daemon 0.15 0.00 0.00 0.00
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1326 1326 nde-netfilter 0.14 0.00 0.00 0.00
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27 27 cpuhp/2 0.13 0.00 0.00 0.00
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631 631 kworker/11:2-rc 0.11 0.00 0.00 0.00
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Dynamic interactive interface of delaytop::
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Interactive keyboard controls during runtime::
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o - Select sort field (CPU, IO, IRQ, Memory, etc.)
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M - Toggle display mode (Default/Memory Verbose)
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q - Quit
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Available sort fields(use -s/--sort or interactive command)::
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cpu(c) - CPU delay
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blkio(i) - I/O delay
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irq(q) - IRQ delay
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mem(m) - Total memory delay
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swapin(s) - Swapin delay (memory verbose mode only)
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freepages(r) - Freepages reclaim delay (memory verbose mode only)
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thrashing(t) - Thrashing delay (memory verbose mode only)
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compact(p) - Compaction delay (memory verbose mode only)
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wpcopy(w) - Write page copy delay (memory verbose mode only)
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Advanced usage examples::
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# ./delaytop -s blkio
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Sorted by IO delay
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# ./delaytop -s mem -M
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Sorted by memory delay in memory verbose mode
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# ./delaytop -p pid
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Print delayacct stats