From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Gilad Ben-Yossef <gilad@benyossef.com>,
linux-kernel@vger.kernel.org,
Frederic Weisbecker <fweisbec@gmail.com>,
Russell King <linux@arm.linux.org.uk>,
Chris Metcalf <cmetcalf@tilera.com>,
linux-mm@kvack.org, Christoph Lameter <cl@linux-foundation.org>,
Matt Mackall <mpm@selenic.com>
Subject: Re: [PATCH 5/5] slub: Only IPI CPUs that have per cpu obj to flush
Date: Mon, 26 Sep 2011 09:36:05 +0200 [thread overview]
Message-ID: <1317022565.9084.60.camel@twins> (raw)
In-Reply-To: <CAOJsxLEHHJyPnCngQceRW04PLKFa3RUQEbc3rLwiOPXa7XZNeQ@mail.gmail.com>
On Mon, 2011-09-26 at 09:54 +0300, Pekka Enberg wrote:
>
> AFAICT, flush_all() isn't all that performance sensitive. Why do we
> want to reduce IPIs here?
Because it can wake up otherwise idle CPUs, wasting power. Or for the
case I care more about, unnecessarily perturb a CPU that didn't actually
have anything to flush but was running something, introducing jitter.
on_each_cpu() things are bad when you have a ton of CPUs (which is
pretty normal these days).
WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Gilad Ben-Yossef <gilad@benyossef.com>,
linux-kernel@vger.kernel.org,
Frederic Weisbecker <fweisbec@gmail.com>,
Russell King <linux@arm.linux.org.uk>,
Chris Metcalf <cmetcalf@tilera.com>,
linux-mm@kvack.org, Christoph Lameter <cl@linux-foundation.org>,
Matt Mackall <mpm@selenic.com>
Subject: Re: [PATCH 5/5] slub: Only IPI CPUs that have per cpu obj to flush
Date: Mon, 26 Sep 2011 09:36:05 +0200 [thread overview]
Message-ID: <1317022565.9084.60.camel@twins> (raw)
In-Reply-To: <CAOJsxLEHHJyPnCngQceRW04PLKFa3RUQEbc3rLwiOPXa7XZNeQ@mail.gmail.com>
On Mon, 2011-09-26 at 09:54 +0300, Pekka Enberg wrote:
>
> AFAICT, flush_all() isn't all that performance sensitive. Why do we
> want to reduce IPIs here?
Because it can wake up otherwise idle CPUs, wasting power. Or for the
case I care more about, unnecessarily perturb a CPU that didn't actually
have anything to flush but was running something, introducing jitter.
on_each_cpu() things are bad when you have a ton of CPUs (which is
pretty normal these days).
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2011-09-26 7:36 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-25 8:54 [PATCH 0/5] Reduce cross CPU IPI interference Gilad Ben-Yossef
2011-09-25 8:54 ` Gilad Ben-Yossef
2011-09-25 8:54 ` [PATCH 1/5] smp: Introduce a generic on_each_cpu_mask function Gilad Ben-Yossef
2011-09-25 8:54 ` Gilad Ben-Yossef
2011-09-25 11:37 ` Sasha Levin
2011-09-25 11:37 ` Sasha Levin
2011-09-26 8:48 ` Peter Zijlstra
2011-09-26 8:48 ` Peter Zijlstra
2011-09-25 8:54 ` [PATCH 2/5] arm: Move arm over to generic on_each_cpu_mask Gilad Ben-Yossef
2011-09-25 8:54 ` Gilad Ben-Yossef
2011-09-25 8:54 ` [PATCH 3/5] tile: Move tile to use " Gilad Ben-Yossef
2011-09-25 8:54 ` Gilad Ben-Yossef
2011-09-25 8:54 ` [PATCH 4/5] mm: Only IPI CPUs to drain local pages if they exist Gilad Ben-Yossef
2011-09-25 8:54 ` Gilad Ben-Yossef
2011-09-26 1:52 ` Shaohua Li
2011-09-26 1:52 ` Shaohua Li
2011-09-26 6:47 ` Gilad Ben-Yossef
2011-09-26 6:47 ` Gilad Ben-Yossef
2011-09-26 15:24 ` Christoph Lameter
2011-09-26 15:24 ` Christoph Lameter
2011-09-27 7:27 ` Gilad Ben-Yossef
2011-09-27 7:27 ` Gilad Ben-Yossef
2011-09-27 16:13 ` Christoph Lameter
2011-09-27 16:13 ` Christoph Lameter
2011-09-26 7:28 ` Peter Zijlstra
2011-09-26 7:28 ` Peter Zijlstra
2011-09-26 8:39 ` Gilad Ben-Yossef
2011-09-26 8:39 ` Gilad Ben-Yossef
2011-09-26 7:29 ` Peter Zijlstra
2011-09-26 7:29 ` Peter Zijlstra
2011-09-25 8:54 ` [PATCH 5/5] slub: Only IPI CPUs that have per cpu obj to flush Gilad Ben-Yossef
2011-09-25 8:54 ` Gilad Ben-Yossef
2011-09-26 6:54 ` Pekka Enberg
2011-09-26 6:54 ` Pekka Enberg
2011-09-26 7:36 ` Peter Zijlstra [this message]
2011-09-26 7:36 ` Peter Zijlstra
2011-09-26 8:07 ` Gilad Ben-Yossef
2011-09-26 8:07 ` Gilad Ben-Yossef
2011-09-26 10:03 ` Pekka Enberg
2011-09-26 10:03 ` Pekka Enberg
2011-09-26 8:10 ` Gilad Ben-Yossef
2011-09-26 8:10 ` Gilad Ben-Yossef
2011-09-26 7:33 ` Peter Zijlstra
2011-09-26 7:33 ` Peter Zijlstra
2011-09-26 8:35 ` Gilad Ben-Yossef
2011-09-26 8:35 ` Gilad Ben-Yossef
2011-09-26 9:28 ` Pekka Enberg
2011-09-26 9:28 ` Pekka Enberg
2011-09-26 9:45 ` Peter Zijlstra
2011-09-26 9:45 ` Peter Zijlstra
2011-09-26 12:05 ` Gilad Ben-Yossef
2011-09-26 12:05 ` Gilad Ben-Yossef
2011-09-26 13:49 ` Gilad Ben-Yossef
2011-09-26 13:49 ` Gilad Ben-Yossef
2011-09-26 7:20 ` [PATCH 0/5] Reduce cross CPU IPI interference Peter Zijlstra
2011-09-26 7:20 ` Peter Zijlstra
2011-09-26 8:43 ` Gilad Ben-Yossef
2011-09-26 8:43 ` Gilad Ben-Yossef
2011-09-26 8:46 ` Peter Zijlstra
2011-09-26 8:46 ` Peter Zijlstra
2011-09-28 13:00 ` Chris Metcalf
2011-09-28 13:00 ` Chris Metcalf
2011-10-02 8:44 ` Gilad Ben-Yossef
2011-10-02 8:44 ` Gilad Ben-Yossef
2011-10-02 14:58 ` Chris Metcalf
2011-10-02 14:58 ` Chris Metcalf
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=1317022565.9084.60.camel@twins \
--to=a.p.zijlstra@chello.nl \
--cc=cl@linux-foundation.org \
--cc=cmetcalf@tilera.com \
--cc=fweisbec@gmail.com \
--cc=gilad@benyossef.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux@arm.linux.org.uk \
--cc=mpm@selenic.com \
--cc=penberg@cs.helsinki.fi \
/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.