From: Peter Zijlstra <peterz@infradead.org>
To: Matt Mackall <mpm@selenic.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Marin Mitov <mitov@issp.bas.bg>,
linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
Andi Kleen <ak@suse.de>
Subject: Re: is minimum udelay() not respected in preemptible SMP kernel-2.6.23?
Date: Thu, 08 Nov 2007 10:11:21 +0100 [thread overview]
Message-ID: <1194513081.6289.130.camel@twins> (raw)
In-Reply-To: <20071108002027.GV17536@waste.org>
On Wed, 2007-11-07 at 18:20 -0600, Matt Mackall wrote:
> This and other cases
> (lots of per_cpu users, IIRC) actually want a migrate_disable() which
> is a proper subset.
The disadvantage of migrate_disable() is that it complicates the
load-balancer but more importantly, that it does bring a form of
latencies with it that are hard to measure. Using preempt_disable() for
these current per-cpu users basically forces them to keep it short.
Which is a GOOD (tm) thing.
If we go overboard with this migrate_disable() stuff we can end up with
a very hard to analyse system that sporadically does weird stuff.
So, please, don't start that again.
Also see:
http://lkml.org/lkml/2007/7/23/338
next prev parent reply other threads:[~2007-11-08 9:11 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-07 17:21 is minimum udelay() not respected in preemptible SMP kernel-2.6.23? Marin Mitov
2007-11-07 20:30 ` Andrew Morton
2007-11-07 23:10 ` Andi Kleen
2007-11-08 0:20 ` Matt Mackall
2007-11-08 0:31 ` Andi Kleen
2007-11-08 1:03 ` Matt Mackall
2007-11-08 1:20 ` Andi Kleen
2007-11-08 2:44 ` Matt Mackall
2007-11-08 11:46 ` Avi Kivity
2007-11-08 15:10 ` Matt Mackall
2007-11-08 9:11 ` Peter Zijlstra [this message]
2007-11-08 15:43 ` Matt Mackall
2007-11-08 11:24 ` Marin Mitov
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=1194513081.6289.130.camel@twins \
--to=peterz@infradead.org \
--cc=ak@suse.de \
--cc=akpm@linux-foundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
--cc=mitov@issp.bas.bg \
--cc=mpm@selenic.com \
--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.