Commit ec710aa8 authored by wangyong's avatar wangyong Committed by Linus Torvalds
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Documentation/accounting/delay-accounting.rst: add thrashing page cache and direct compact 

Add thrashing page cache and direct compact related descriptions and
update the usage of getdelays userspace utility.

The following patches modifications have been updated:
https://lore.kernel.org/all/20190312102002.31737-4-jinpuwang@gmail.com/
https://lore.kernel.org/all/1638619795-71451-1-git-send-email-
wang.yong12@zte.com.cn/

Link: https://lkml.kernel.org/r/1639583021-92977-1-git-send-email-wang.yong12@zte.com.cn


Signed-off-by: default avatarwangyong <wang.yong12@zte.com.cn>
Reviewed-by: default avatarYang Yang <yang.yang29@zte.com.cn>
Reported-by: default avatarZeal Robot <zealci@zte.com.cn>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1193829d

Documentation/accounting/delay-accounting.rst

+27 −28
Original line number Diff line number Diff line
@@ -13,6 +13,8 @@ a) waiting for a CPU (while being runnable) 
b) completion of synchronous block I/O initiated by the task

c) swapping in pages

d) memory reclaim

e) thrashing page cache

f) direct compact



and makes these statistics available to userspace through

the taskstats interface.
@@ -41,11 +43,12 @@ generic data structure to userspace corresponding to per-pid and per-tgid 
statistics. The delay accounting functionality populates specific fields of

this structure. See



     include/linux/taskstats.h

     include/uapi/linux/taskstats.h



for a description of the fields pertaining to delay accounting.

It will generally be in the form of counters returning the cumulative

delay seen for cpu, sync block I/O, swapin, memory reclaim etc.

delay seen for cpu, sync block I/O, swapin, memory reclaim, thrash page

cache, direct compact etc.



Taking the difference of two successive readings of a given

counter (say cpu_delay_total) for a task will give the delay
@@ -88,41 +91,37 @@ seen. 


General format of the getdelays command::



	getdelays [-t tgid] [-p pid] [-c cmd...]



	getdelays [-dilv] [-t tgid] [-p pid]



Get delays, since system boot, for pid 10::



	# ./getdelays -p 10

	# ./getdelays -d -p 10

	(output similar to next case)



Get sum of delays, since system boot, for all pids with tgid 5::



	# ./getdelays -t 5





	CPU	count	real total	virtual total	delay total

		7876	92005750	100000000	24001500

	IO	count	delay total

		0	0

	SWAP	count	delay total

		0	0

	RECLAIM	count	delay total

		0	0

	# ./getdelays -d -t 5

	print delayacct stats ON

	TGID	5



Get delays seen in executing a given simple command::



  # ./getdelays -c ls /

	CPU             count     real total  virtual total    delay total  delay average

	                    8        7000000        6872122        3382277          0.423ms

	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

	                    0              0              0ms



  bin   data1  data3  data5  dev  home  media  opt   root  srv        sys  usr

  boot  data2  data4  data6  etc  lib   mnt    proc  sbin  subdomain  tmp  var

Get IO accounting for pid 1, it works only with -p::



	# ./getdelays -i -p 1

	printing IO accounting

	linuxrc: read=65536, write=0, cancelled_write=0



  CPU	count	real total	virtual total	delay total

	6	4000250		4000000		0

  IO	count	delay total

	0	0

  SWAP	count	delay total

	0	0

  RECLAIM	count	delay total

	0	0
 
The above command can be used with -v to get more debug information.