Commit c25822cc authored by Fan Yu's avatar Fan Yu Committed by Andrew Morton
Browse files

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: default avatarFan Yu <fan.yu9@zte.com.cn>
Reviewed-by: default avatarxu xin <xu.xin16@zte.com.cn>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 0c10f9cd

Documentation/accounting/delay-accounting.rst

+58 −33
Original line number Diff line number Diff line
@@ -134,47 +134,72 @@ The above command can be used with -v to get more debug information. 


After the system starts, use `delaytop` to get the system-wide delay information,

which includes system-wide PSI information and Top-N high-latency tasks.

Note: PSI support requires `CONFIG_PSI=y` and `psi=1` for full functionality.



`delaytop` 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.

`delaytop` is an interactive tool for monitoring system pressure and task delays.

It supports multiple sorting options, display modes, and real-time keyboard controls.



Get PSI information and Top-N tasks delay, since system boot::

Basic usage with default settings (sorts by CPU delay, shows top 20 tasks, refreshes every 2 seconds)::



	bash# ./delaytop

	System Pressure Information: (avg10/avg60/avg300/total)

	CPU some:       0.0%/   0.0%/   0.0%/     345(ms)

	System Pressure Information: (avg10/avg60vg300/total)

	CPU some:       0.0%/   0.0%/   0.0%/  106137(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)

	IO full:        0.0%/   0.0%/   0.0%/    2240(ms)

	IO some:        0.0%/   0.0%/   0.0%/    2783(ms)

	IRQ full:       0.0%/   0.0%/   0.0%/       0(ms)

	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)

	----------------------------------------------------------------------------------------------

	  161    161  zombie_memcg_re   1.40    0.00    0.00    0.00    0.00    0.00    0.00    0.00

	  130    130  blkcg_punt_bio    1.37    0.00    0.00    0.00    0.00    0.00    0.00    0.00

	  444    444  scsi_tmf_0        0.73    0.00    0.00    0.00    0.00    0.00    0.00    0.00

	 1280   1280  rsyslogd          0.53    0.04    0.00    0.00    0.00    0.00    0.00    0.00

	   12     12  ksoftirqd/0       0.47    0.00    0.00    0.00    0.00    0.00    0.00    0.00

	 1277   1277  nbd-server        0.44    0.00    0.00    0.00    0.00    0.00    0.00    0.00

	  308    308  kworker/2:2-sys   0.41    0.00    0.00    0.00    0.00    0.00    0.00    0.00

	   55     55  netns             0.36    0.00    0.00    0.00    0.00    0.00    0.00    0.00

	 1187   1187  acpid             0.31    0.03    0.00    0.00    0.00    0.00    0.00    0.00

	 6184   6184  kworker/1:2-sys   0.24    0.00    0.00    0.00    0.00    0.00    0.00    0.00

	  186    186  kaluad            0.24    0.00    0.00    0.00    0.00    0.00    0.00    0.00

	   18     18  ksoftirqd/1       0.24    0.00    0.00    0.00    0.00    0.00    0.00    0.00

	  185    185  kmpath_rdacd      0.23    0.00    0.00    0.00    0.00    0.00    0.00    0.00

	  190    190  kstrp             0.23    0.00    0.00    0.00    0.00    0.00    0.00    0.00

	 2759   2759  agetty            0.20    0.03    0.00    0.00    0.00    0.00    0.00    0.00

	 1190   1190  kworker/0:3-sys   0.19    0.00    0.00    0.00    0.00    0.00    0.00    0.00

	 1272   1272  sshd              0.15    0.04    0.00    0.00    0.00    0.00    0.00    0.00

	 1156   1156  license           0.15    0.11    0.00    0.00    0.00    0.00    0.00    0.00

	  134    134  md                0.13    0.00    0.00    0.00    0.00    0.00    0.00    0.00

	 6142   6142  kworker/3:2-xfs   0.13    0.00    0.00    0.00    0.00    0.00    0.00    0.00



Dynamic interactive interface of delaytop::

	[o]sort [M]memverbose [q]quit

	Top 20 processes (sorted by cpu delay):

		PID      TGID  COMMAND           CPU(ms)   IO(ms)  IRQ(ms)  MEM(ms)

	------------------------------------------------------------------------

		110       110  kworker/15:0H-s   27.91     0.00     0.00     0.00

		57        57  cpuhp/7            3.18     0.00     0.00     0.00

		99        99  cpuhp/14           2.97     0.00     0.00     0.00

		51        51  cpuhp/6            0.90     0.00     0.00     0.00

		44        44  kworker/4:0H-sy    0.80     0.00     0.00     0.00

		60        60  ksoftirqd/7        0.74     0.00     0.00     0.00

		76        76  idle_inject/10     0.31     0.00     0.00     0.00

		100       100  idle_inject/14     0.30     0.00     0.00     0.00

		1309      1309  systemsettings     0.29     0.00     0.00     0.00

		45        45  cpuhp/5            0.22     0.00     0.00     0.00

		63        63  cpuhp/8            0.20     0.00     0.00     0.00

		87        87  cpuhp/12           0.18     0.00     0.00     0.00

		93        93  cpuhp/13           0.17     0.00     0.00     0.00

		1265      1265  acpid              0.17     0.00     0.00     0.00

		1552      1552  sshd               0.17     0.00     0.00     0.00

		2584      2584  sddm-helper        0.16     0.00     0.00     0.00

		1284      1284  rtkit-daemon       0.15     0.00     0.00     0.00

		1326      1326  nde-netfilter      0.14     0.00     0.00     0.00

		27        27  cpuhp/2            0.13     0.00     0.00     0.00

		631       631  kworker/11:2-rc    0.11     0.00     0.00     0.00



Interactive keyboard controls during runtime::



	o - Select sort field (CPU, IO, IRQ, Memory, etc.)

	M - Toggle display mode (Default/Memory Verbose)

	q - Quit



Available sort fields(use -s/--sort or interactive command)::



	cpu(c)       - CPU delay

	blkio(i)     - I/O delay

	irq(q)       - IRQ delay

	mem(m)       - Total memory delay

	swapin(s)    - Swapin delay (memory verbose mode only)

	freepages(r) - Freepages reclaim delay (memory verbose mode only)

	thrashing(t) - Thrashing delay (memory verbose mode only)

	compact(p)   - Compaction delay (memory verbose mode only)

	wpcopy(w)    - Write page copy delay (memory verbose mode only)



Advanced usage examples::



	# ./delaytop -s blkio

	Sorted by IO delay



	# ./delaytop -s mem -M

	Sorted by memory delay in memory verbose mode



	# ./delaytop -p pid

	Print delayacct stats