From: Chen Yu <yu.c.chen@intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Vincent Guittot <vincent.guittot@linaro.org>,
Tim Chen <tim.c.chen@intel.com>,
Mel Gorman <mgorman@techsingularity.net>,
Juri Lelli <juri.lelli@redhat.com>,
Rik van Riel <riel@surriel.com>, Aaron Lu <aaron.lu@intel.com>,
Abel Wu <wuyun.abel@bytedance.com>,
K Prateek Nayak <kprateek.nayak@amd.com>,
Yicong Yang <yangyicong@hisilicon.com>,
"Gautham R . Shenoy" <gautham.shenoy@amd.com>,
Ingo Molnar <mingo@redhat.com>,
"Dietmar Eggemann" <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Valentin Schneider <vschneid@redhat.com>,
<linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH] sched/fair: Choose the CPU where short task is running during wake up
Date: Sat, 17 Sep 2022 21:55:45 +0800 [thread overview]
Message-ID: <YyXR4YgHeTR4Negc@chenyu5-mobl1> (raw)
In-Reply-To: <YyRhvEGS4ivPGf+z@hirez.programming.kicks-ass.net>
On 2022-09-16 at 13:45:00 +0200, Peter Zijlstra wrote:
> On Fri, Sep 16, 2022 at 12:54:07AM +0800, Chen Yu wrote:
> > And the rq lock bottleneck is composed of two paths(perf profile):
> >
> > (path1):
> > raw_spin_rq_lock_nested.constprop.0;
> > try_to_wake_up;
> > default_wake_function;
> > autoremove_wake_function;
> > __wake_up_common;
> > __wake_up_common_lock;
> > __wake_up_sync_key;
> > pipe_write;
> > new_sync_write;
> > vfs_write;
> > ksys_write;
> > __x64_sys_write;
> > do_syscall_64;
> > entry_SYSCALL_64_after_hwframe;write
>
> Can you please addr2line -i the raw_spin_rq_lock callsite so we know which is
> the one causing grief?
>
> Specifically; I'm worried about PSI, psi_ttwu_dequeue() can cause ttwu()
> to take _2_ rq->lock, which absolutely blows for this case.
Above perf profile result was captured with 'psi=0' appended in the boot
commandline, and with NO_TTWU_QUEUE on 6.0-rc4. To narrow down we disabled
psi the first time we saw a rq lock contention. But even with psi=0 we still
observe the rq lock contention.
To confirm this, the 'perf report -F+period,srcline' was used to leverage
addr2line to parse the line. However it seems that with DWARF v4 enabled
in the kernel, the rq lock issue could not be reproduced. So I hacked the
code to make ttwu_queue() non-static, and perf profile shows that it grabs
the rq lock:
raw_spin_rq_lock_nested.constprop.0;
ttwu_queue; <----------
try_to_wake_up;
default_wake_function;
autoremove_wake_function;
__wake_up_common;
__wake_up_common_lock;
__wake_up_sync_key;
pipe_write;
vfs_write;
ksys_write;
__x64_sys_write;
do_syscall_64;
entry_SYSCALL_64_after_hwframe;
write
Then if TTWU_QUEUE is enabled, the rq lock contention issue could
not be reproduced, but long idle duration was still observed due to
sched_ttwu_pending(as descibed in the commit log).
thanks,
Chenyu
next prev parent reply other threads:[~2022-09-17 13:56 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-15 16:54 [RFC PATCH] sched/fair: Choose the CPU where short task is running during wake up Chen Yu
2022-09-15 17:10 ` Tim Chen
2022-09-16 10:49 ` Chen Yu
2022-09-16 11:45 ` Peter Zijlstra
2022-09-17 13:55 ` Chen Yu [this message]
2022-09-16 11:47 ` Peter Zijlstra
2022-09-17 14:15 ` Chen Yu
2022-09-26 5:50 ` K Prateek Nayak
2022-09-26 14:39 ` Gautham R. Shenoy
2022-09-29 16:58 ` K Prateek Nayak
2022-09-30 17:26 ` Chen Yu
2022-09-29 5:25 ` Chen Yu
2022-09-29 6:59 ` Honglei Wang
2022-09-29 17:34 ` K Prateek Nayak
2022-09-30 0:58 ` Honglei Wang
2022-09-30 16:03 ` Chen Yu
2022-09-29 17:19 ` K Prateek Nayak
2022-09-29 8:00 ` Vincent Guittot
2022-09-30 16:53 ` Chen Yu
2022-10-03 12:42 ` Vincent Guittot
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=YyXR4YgHeTR4Negc@chenyu5-mobl1 \
--to=yu.c.chen@intel.com \
--cc=aaron.lu@intel.com \
--cc=bristot@redhat.com \
--cc=bsegall@google.com \
--cc=dietmar.eggemann@arm.com \
--cc=gautham.shenoy@amd.com \
--cc=juri.lelli@redhat.com \
--cc=kprateek.nayak@amd.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mgorman@techsingularity.net \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=riel@surriel.com \
--cc=rostedt@goodmis.org \
--cc=tim.c.chen@intel.com \
--cc=vincent.guittot@linaro.org \
--cc=vschneid@redhat.com \
--cc=wuyun.abel@bytedance.com \
--cc=yangyicong@hisilicon.com \
/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).