From: Jeff Garzik <jgarzik@pobox.com>
To: Roland Dreier <roland@topspin.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Preempt? (was Re: Cannot enable DMA on SATA drive (SCSI-libsata, VIA SATA))
Date: Tue, 05 Oct 2004 21:11:59 -0400 [thread overview]
Message-ID: <4163465F.6070309@pobox.com> (raw)
In-Reply-To: <52is9or78f.fsf_-_@topspin.com>
Roland Dreier wrote:
> Jeff> I strongly recommend disabling kernel preemption. It is a
> Jeff> hack that hides bugs.
>
> Why do you say that? Preempt seems to be the cleanest way to low
> latency, and if anything it exposes locking bugs and races rather than
> hiding anything.
Clean? Hardly. It breaks up code paths that were never written to be
broken up. The proper fix is to locate and fix high latency code paths.
Preempt does nothing but hide those high latency code paths, and
discourage people from seeking a better solution.
Fix the drivers, rather than bandaid over them with preempt.
If all code paths in the kernel were low latency, then you would not
need preempt at all.
Jeff
next prev parent reply other threads:[~2004-10-06 1:12 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <4136E7EF00073144@mail-3.tiscali.it>
2004-10-06 0:30 ` Cannot enable DMA on SATA drive (SCSI-libsata, VIA SATA) Gianluca Cecchi
2004-10-06 0:54 ` Jeff Garzik
2004-10-06 1:00 ` Preempt? (was Re: Cannot enable DMA on SATA drive (SCSI-libsata, VIA SATA)) Roland Dreier
2004-10-06 1:11 ` Jeff Garzik [this message]
2004-10-06 1:28 ` Nick Piggin
2004-10-06 1:32 ` Nick Piggin
2004-10-06 1:40 ` Jeff Garzik
2004-10-06 1:52 ` Robert Love
2004-10-06 1:55 ` Jeff Garzik
2004-10-06 2:02 ` Nick Piggin
2004-10-06 2:07 ` Jeff Garzik
2004-10-06 2:28 ` Nick Piggin
2004-10-06 3:17 ` Andrea Arcangeli
2004-10-06 3:27 ` Jeff Garzik
2004-10-06 3:43 ` Nick Piggin
2004-10-06 3:59 ` Jeff Garzik
2004-10-06 4:05 ` Lee Revell
2004-10-06 4:22 ` Nick Piggin
2004-10-06 15:16 ` Aleksandar Milivojevic
2004-10-06 4:03 ` Andrea Arcangeli
2004-10-06 4:08 ` Jeff Garzik
2004-10-06 4:16 ` Lee Revell
2004-10-06 4:26 ` Nick Piggin
2004-10-06 4:46 ` Andrew Morton
2004-10-06 6:04 ` Jeff Garzik
2004-10-06 6:16 ` Andrew Morton
2004-10-06 13:38 ` Jeff Sipek
2004-10-06 4:12 ` Lee Revell
2004-10-06 3:34 ` Nick Piggin
2004-10-06 2:07 ` Robert Love
2004-10-06 2:30 ` Nick Piggin
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