From: Nick Piggin <npiggin@suse.de>
To: Lee Revell <rlrevell@joe-job.com>
Cc: Davide Libenzi <davidel@xmailserver.org>,
Oleg Nesterov <oleg@tv-sign.ru>,
Ravikiran G Thirumalai <kiran@scalex86.org>,
Ingo Molnar <mingo@elte.hu>,
Nikita Danilov <nikita@clusterfs.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [patch] queued spinlocks (i386)
Date: Fri, 30 Mar 2007 04:17:17 +0200 [thread overview]
Message-ID: <20070330021717.GF19407@wotan.suse.de> (raw)
In-Reply-To: <75b66ecd0703291906q265f9cc7g486cf65484ba8393@mail.gmail.com>
On Thu, Mar 29, 2007 at 10:06:41PM -0400, Lee Revell wrote:
> On 3/29/07, Davide Libenzi <davidel@xmailserver.org> wrote:
> >On Thu, 29 Mar 2007, Oleg Nesterov wrote:
> >
> >> On 03/28, Nick Piggin wrote:
> >> >
> >> > Well with my queued spinlocks, all that lockbreak stuff can just come
> >out
> >> > of the spin_lock, break_lock out of the spinlock structure, and
> >> > need_lockbreak just becomes (lock->qhead - lock->qtail > 1).
> >>
> >> Q: queued spinlocks are not CONFIG_PREEMPT friendly,
> >
> >Why? Is CONFIG_PREEMPT friendly to anyone? :)
>
> Until someone fixes all the places in the kernel where scheduling can
> be held off for tens of milliseconds, CONFIG_PREEMPT will be an
> absolute requirement for many applications like audio and gaming.
There's nothing wrong with CONFIG_PREEMPT for those users. We have
a few other performance concessions activated with CONFIG_PREEMPT on.
I think a usual upper of a few miliseconds (especially for SMP) is
reasonable for a non preempt kernel.
next prev parent reply other threads:[~2007-03-30 2:17 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-25 15:54 [patch] queued spinlocks (i386) Oleg Nesterov
2007-03-27 15:22 ` Andi Kleen
2007-03-28 7:04 ` Nick Piggin
2007-03-29 18:42 ` Oleg Nesterov
2007-03-29 22:16 ` Davide Libenzi
2007-03-30 2:06 ` Lee Revell
2007-03-30 2:17 ` Nick Piggin [this message]
2007-03-30 4:44 ` Lee Revell
2007-03-30 1:53 ` Nick Piggin
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