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authorYang Yang2022-06-01 15:55:25 -0700
committerakpm2022-06-01 15:55:25 -0700
commit662ce1dc9caf493c309200edbe38d186f1ea20d0 (patch)
treee49eeda0a61590b5843d47d1be17dbb18cf3aaa1 /Documentation
parent54eb8462f21fb170a05ad64620f0d8d0cf2b7fb5 (diff)
delayacct: track delays from write-protect copy
Delay accounting does not track the delay of write-protect copy. When tasks trigger many write-protect copys(include COW and unsharing of anonymous pages[1]), it may spend a amount of time waiting for them. To get the delay of tasks in write-protect copy, could help users to evaluate the impact of using KSM or fork() or GUP. Also update tools/accounting/getdelays.c: / # ./getdelays -dl -p 231 print delayacct stats ON listen forever PID 231 CPU count real total virtual total delay total delay average 6247 1859000000 2154070021 1674255063 0.268ms 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 3 72758 0ms WPCOPY count delay total delay average 3635 271567604 0ms [1] commit 31cc5bc4af70("mm: support GUP-triggered unsharing of anonymous pages") Link: https://lkml.kernel.org/r/20220409014342.2505532-1-yang.yang29@zte.com.cn Signed-off-by: Yang Yang <yang.yang29@zte.com.cn> Reviewed-by: David Hildenbrand <david@redhat.com> Reviewed-by: Jiang Xuexin <jiang.xuexin@zte.com.cn> Reviewed-by: Ran Xiaokai <ran.xiaokai@zte.com.cn> Reviewed-by: wangyong <wang.yong12@zte.com.cn> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Balbir Singh <bsingharora@gmail.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/accounting/delay-accounting.rst5
1 files changed, 4 insertions, 1 deletions
diff --git a/Documentation/accounting/delay-accounting.rst b/Documentation/accounting/delay-accounting.rst
index 197fe319cbec..241d1a87f2cd 100644
--- a/Documentation/accounting/delay-accounting.rst
+++ b/Documentation/accounting/delay-accounting.rst
@@ -15,6 +15,7 @@ c) swapping in pages
d) memory reclaim
e) thrashing page cache
f) direct compact
+g) write-protect copy
and makes these statistics available to userspace through
the taskstats interface.
@@ -48,7 +49,7 @@ this structure. See
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, thrash page
-cache, direct compact etc.
+cache, direct compact, write-protect copy etc.
Taking the difference of two successive readings of a given
counter (say cpu_delay_total) for a task will give the delay
@@ -117,6 +118,8 @@ Get sum of delays, since system boot, for all pids with tgid 5::
0 0 0ms
COMPACT count delay total delay average
0 0 0ms
+ WPCOPY count delay total delay average
+ 0 0 0ms
Get IO accounting for pid 1, it works only with -p::