From: Peter Zijlstra <peterz@infradead.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: "Arjan van de Ven" <arjan@linux.intel.com>,
"Fernando Luis Vázquez Cao" <fernando_b1@lab.ntt.co.jp>,
"Frederic Weisbecker" <fweisbec@gmail.com>,
"Ingo Molnar" <mingo@kernel.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
"Tetsuo Handa" <penguin-kernel@I-love.SAKURA.ne.jp>,
"Andrew Morton" <akpm@linux-foundation.org>
Subject: Re: [PATCH 2/4] nohz: Synchronize sleep time stats with seqlock
Date: Wed, 21 Aug 2013 16:23:56 +0200 [thread overview]
Message-ID: <20130821142356.GC31370@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20130821123311.GA31370@twins.programming.kicks-ass.net>
On Wed, Aug 21, 2013 at 02:33:11PM +0200, Peter Zijlstra wrote:
> On Wed, Aug 21, 2013 at 01:35:51PM +0200, Oleg Nesterov wrote:
> > On 08/21, Peter Zijlstra wrote:
>
> > > Yes its the right rq, but the wrong time.
> >
> > Hmm. Just in case, it is not that I think this patch really makes sense,
> > but I'd like to understand why do you think it is wrong.
>
> > But it is not "after it switches out", it is after it switched back.
>
> D'uh I was being particularly dense it seems :/
>
> Yes I think it is correct. You're now trading two atomic ops on a
> different cacheline than rq->lock for one atomic op on the rq->lock.
>
> Might be a win, esp. since hopefully there's a fair chance its the same
> runqueue.
The other consideration is that this adds two branches to the normal
schedule path. I really don't know what the regular ratio between
schedule() and io_schedule() is -- and I suspect it can very much depend
on workload -- but it might be a net loss due to that, even if it makes
io_schedule() 'lots' cheaper.
next prev parent reply other threads:[~2013-08-21 14:24 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-16 15:42 [PATCH RESEND 0/4] nohz: Fix racy sleeptime stats Frederic Weisbecker
2013-08-16 15:42 ` [PATCH 1/4] nohz: Only update sleeptime stats locally Frederic Weisbecker
2013-08-18 16:49 ` Oleg Nesterov
2013-08-18 21:38 ` Frederic Weisbecker
2013-08-18 17:04 ` Oleg Nesterov
2013-08-19 18:05 ` Stratos Karafotis
2013-08-16 15:42 ` [PATCH 2/4] nohz: Synchronize sleep time stats with seqlock Frederic Weisbecker
2013-08-16 16:02 ` Oleg Nesterov
2013-08-16 16:20 ` Frederic Weisbecker
2013-08-16 16:26 ` Oleg Nesterov
2013-08-16 16:46 ` Frederic Weisbecker
2013-08-16 16:49 ` Oleg Nesterov
2013-08-16 17:12 ` Frederic Weisbecker
2013-08-18 16:36 ` Oleg Nesterov
2013-08-18 21:25 ` Frederic Weisbecker
2013-08-19 10:58 ` Peter Zijlstra
2013-08-19 15:44 ` Arjan van de Ven
2013-08-19 15:47 ` Arjan van de Ven
2013-08-19 11:10 ` Peter Zijlstra
2013-08-19 11:15 ` Peter Zijlstra
2013-08-20 6:59 ` Fernando Luis Vázquez Cao
2013-08-20 8:44 ` Peter Zijlstra
2013-08-20 15:29 ` Frederic Weisbecker
2013-08-20 15:33 ` Arjan van de Ven
2013-08-20 15:35 ` Frederic Weisbecker
2013-08-20 15:41 ` Arjan van de Ven
2013-08-20 15:31 ` Arjan van de Ven
2013-08-20 16:01 ` Peter Zijlstra
2013-08-20 16:33 ` Oleg Nesterov
2013-08-20 17:54 ` Peter Zijlstra
2013-08-20 18:25 ` Oleg Nesterov
2013-08-21 8:31 ` Peter Zijlstra
2013-08-21 11:35 ` Oleg Nesterov
2013-08-21 12:33 ` Peter Zijlstra
2013-08-21 14:23 ` Peter Zijlstra [this message]
2013-08-21 16:41 ` Oleg Nesterov
2013-10-01 14:05 ` Frederic Weisbecker
2013-10-01 14:26 ` Frederic Weisbecker
2013-10-01 14:27 ` Frederic Weisbecker
2013-10-01 14:49 ` Frederic Weisbecker
2013-10-01 15:00 ` Peter Zijlstra
2013-10-01 15:21 ` Frederic Weisbecker
2013-10-01 15:56 ` Peter Zijlstra
2013-10-01 16:47 ` Frederic Weisbecker
2013-10-01 16:59 ` Peter Zijlstra
2013-10-02 12:45 ` Frederic Weisbecker
2013-10-02 12:50 ` Peter Zijlstra
2013-10-02 14:35 ` Arjan van de Ven
2013-10-02 16:01 ` Frederic Weisbecker
2013-08-21 12:48 ` Peter Zijlstra
2013-08-21 17:09 ` Oleg Nesterov
2013-08-21 18:31 ` Peter Zijlstra
2013-08-21 18:32 ` Oleg Nesterov
2013-08-20 22:18 ` Frederic Weisbecker
2013-08-21 11:49 ` Oleg Nesterov
2013-08-20 6:21 ` Fernando Luis Vázquez Cao
2013-08-20 21:55 ` Frederic Weisbecker
2013-08-16 16:32 ` Frederic Weisbecker
2013-08-16 16:33 ` Oleg Nesterov
2013-08-16 16:49 ` Frederic Weisbecker
2013-08-16 16:37 ` Frederic Weisbecker
2013-08-18 16:54 ` Oleg Nesterov
2013-08-18 21:40 ` Frederic Weisbecker
2013-08-16 15:42 ` [PATCH 3/4] nohz: Consolidate sleep time stats read code Frederic Weisbecker
2013-08-18 17:00 ` Oleg Nesterov
2013-08-18 21:47 ` Frederic Weisbecker
2013-08-16 15:42 ` [PATCH 4/4] nohz: Convert a few places to use local per cpu accesses Frederic Weisbecker
2013-08-16 16:00 ` Peter Zijlstra
2013-08-16 16:12 ` Frederic Weisbecker
2013-08-16 16:19 ` Oleg Nesterov
2013-08-16 16:34 ` Frederic Weisbecker
2013-08-20 18:15 ` [PATCH RESEND 0/4] nohz: Fix racy sleeptime stats Oleg Nesterov
2013-08-21 8:28 ` Peter Zijlstra
2013-08-21 11:42 ` Oleg Nesterov
-- strict thread matches above, loose matches on Subject: below --
2014-05-07 13:41 [PATCH 1/4] nohz: Only update sleeptime stats locally Denys Vlasenko
2014-05-07 13:41 ` [PATCH 2/4] nohz: Synchronize sleep time stats with seqlock Denys Vlasenko
2014-04-24 18:45 [PATCH 1/4] nohz: Only update sleeptime stats locally Denys Vlasenko
2014-04-24 18:45 ` [PATCH 2/4] nohz: Synchronize sleep time stats with seqlock Denys Vlasenko
2013-08-09 0:54 [PATCH 0/4] nohz: Fix racy sleeptime stats Frederic Weisbecker
2013-08-09 0:54 ` [PATCH 2/4] nohz: Synchronize sleep time stats with seqlock Frederic Weisbecker
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=20130821142356.GC31370@twins.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=akpm@linux-foundation.org \
--cc=arjan@linux.intel.com \
--cc=fernando_b1@lab.ntt.co.jp \
--cc=fweisbec@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=oleg@redhat.com \
--cc=penguin-kernel@I-love.SAKURA.ne.jp \
--cc=tglx@linutronix.de \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.