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
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