From: Scott Wood <swood@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Rik van Riel <riel@surriel.com>, Mel Gorman <mgorman@suse.de>,
linux-kernel@vger.kernel.org,
linux-rt-users <linux-rt-users@vger.kernel.org>
Subject: Re: [RFC PATCH 1/3] sched/fair: Call newidle_balance() from finish_task_switch()
Date: Tue, 28 Apr 2020 18:20:32 -0500 [thread overview]
Message-ID: <89043649a64fc97dd90eb25c85bcc8f65483cf4f.camel@redhat.com> (raw)
In-Reply-To: <20200428230204.GE16027@hirez.programming.kicks-ass.net>
On Wed, 2020-04-29 at 01:02 +0200, Peter Zijlstra wrote:
> On Tue, Apr 28, 2020 at 05:55:03PM -0500, Scott Wood wrote:
> > On Wed, 2020-04-29 at 00:09 +0200, Peter Zijlstra wrote:
> > > Also, if you move it this late, this is entirely the wrong place. If
> > > you
> > > do it after the context switch either use the balance_callback or put
> > > it
> > > in the idle path.
> > >
> > > But what Valentin said; this needs a fair bit of support, the whole
> > > reason we've never done this is to avoid that double context switch...
> > >
> >
> > balance_callback() enters with the rq lock held but BH not separately
>
> BH? softirqs you mean? Pray tell more.
In https://lore.kernel.org/lkml/5122CD9C.9070702@oracle.com/ the need to
keep softirqs disabled during rebalance was brought up, but simply wrapping
the lock dropping in local_bh_enable()/local_bh_disable() meant that
local_bh_enable() would be called with interrupts disabled, which isn't
allowed.
> > disabled, which interferes with the ability to enable interrupts but not
> > BH.
> > It also gets called from rt_mutex_setprio() and __sched_setscheduler(),
> > and
> > I didn't want the caller of those to be stuck with the latency.
>
> You're not reading it right.
Could you elaborate?
-Scott
next prev parent reply other threads:[~2020-04-28 23:20 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-28 5:02 [RFC PATCH 0/3] newidle_balance() latency mitigation Scott Wood
2020-04-28 5:02 ` [RFC PATCH 1/3] sched/fair: Call newidle_balance() from finish_task_switch() Scott Wood
2020-04-28 21:37 ` Valentin Schneider
2020-04-28 22:09 ` Peter Zijlstra
2020-04-28 22:55 ` Scott Wood
2020-04-28 23:02 ` Peter Zijlstra
2020-04-28 23:20 ` Scott Wood [this message]
2020-04-29 9:05 ` Peter Zijlstra
2020-04-30 1:31 ` Scott Wood
2020-05-11 10:58 ` Peter Zijlstra
2020-05-11 12:13 ` Peter Zijlstra
2020-04-28 22:33 ` Scott Wood
2020-04-29 12:00 ` Valentin Schneider
2020-04-29 8:27 ` Vincent Guittot
2020-04-30 1:36 ` Scott Wood
2020-04-28 5:02 ` [RFC PATCH 2/3] sched/fair: Enable interrupts when dropping lock in newidle_balance() Scott Wood
2020-04-28 5:02 ` [RFC PATCH 3/3] sched,rt: break out of load balancing if an RT task appears Scott Wood
2020-04-28 21:56 ` Valentin Schneider
2020-04-28 22:33 ` Scott Wood
2020-04-28 22:52 ` Scott Wood
2020-04-29 12:01 ` Valentin Schneider
2020-04-28 13:27 ` [RFC PATCH 0/3] newidle_balance() latency mitigation Steven Rostedt
2020-04-29 23:13 ` Valentin Schneider
2020-04-30 7:44 ` Vincent Guittot
2020-04-30 10:14 ` Valentin Schneider
2020-04-30 12:42 ` Vincent Guittot
2020-04-30 13:56 ` Valentin Schneider
2020-04-30 12:48 ` 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=89043649a64fc97dd90eb25c85bcc8f65483cf4f.camel@redhat.com \
--to=swood@redhat.com \
--cc=dietmar.eggemann@arm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-rt-users@vger.kernel.org \
--cc=mgorman@suse.de \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=riel@surriel.com \
--cc=rostedt@goodmis.org \
--cc=valentin.schneider@arm.com \
--cc=vincent.guittot@linaro.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).