From: Milian Wolff <milian.wolff@kdab.com>
To: perf group <linux-perf-users@vger.kernel.org>
Subject: What unit is used by "period" for sleep time profiling?
Date: Tue, 23 Feb 2016 15:08:20 +0100 [thread overview]
Message-ID: <2312924.dtc4z5l04H@milian-kdab2> (raw)
[-- Attachment #1: Type: text/plain, Size: 1637 bytes --]
Hey all,
following the "profiling sleep times" steps on the perf wiki at [1], we can
get some "Period" numbers. The wiki e.g. shows a number of "502408738". To
match the results to the code snippet, I believe the unit is 0.1ns - can
somebody confirm that please? I.e. 79.59% of should match 40ms, and 20.15%
should match the 10ms.
Where does this odd unit come from, and could I patch perf to display readable
times instead?
To make things worse, I actually have trouble reproducing the values shown in
the wiki - is there an off-by-one error somewhere?
time perf record -e ... sleep 5
real 0m5.224s
user 0m0.033s
sys 0m0.130s
perf inject ...
perf report --stdio --show-total-period -i perf.data
# Children Self Period Trace output
# ........ ........ ............ .........................................
#
100.00% 100.00% 40004252280 sleep:27134 [120] S ==> swapper/0:0 [120]
|
---__schedule
schedule
do_nanosleep
hrtimer_nanosleep
sys_nanosleep
entry_SYSCALL_64_fastpath
__nanosleep
0x4040ff
0x403f58
0x4016da
__libc_start_main
0x4017c9
My above formula would now tell me that sleep only slept for 4s, not 5s...
That looks very wrong!
[1]: https://perf.wiki.kernel.org/index.php/Tutorial#Profiling_sleep_times
--
Milian Wolff | milian.wolff@kdab.com | Software Engineer
KDAB (Deutschland) GmbH&Co KG, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt Experts
[-- Attachment #2: smime.p7s --]
[-- Type: application/pkcs7-signature, Size: 5903 bytes --]
next reply other threads:[~2016-02-23 14:08 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-23 14:08 Milian Wolff [this message]
2016-02-23 17:45 ` What unit is used by "period" for sleep time profiling? Taeung Song
2016-02-23 19:29 ` Milian Wolff
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=2312924.dtc4z5l04H@milian-kdab2 \
--to=milian.wolff@kdab.com \
--cc=linux-perf-users@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).