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List:       linux-audio-dev
Subject:    Re: [linux-audio-dev] huge latency peaks with 2.4.10-smp kernel
From:       Kai Vehmanen <kai.vehmanen () wakkanet ! fi>
Date:       2001-10-19 10:31:10
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On Fri, 19 Oct 2001, Takashi Iwai wrote:

[preemptive kernel patch] 
> However even PE patched kernel can cause unacceptably high latency.
> PE patch checks context switching with help of spinlock/unlock hacks.
> Thus it cannot overcome the long spinlock itself, which can be seen in
> VM and fs.  Consequently PE patch requires also the LL'ish
> preemption/scheduling checks inside the long locked loops to reduce
> the high peaks.

And given that a) PE-patch "just" uses the existing SMP-lock points,
and b) I just reported +3000msec breaks running a SMP-kernel.

But of course, it's clear that if a piece of kernel code halts an
SMP-machine for that long, it's not just a low-latency issue anymore - the
code-path in question needs tuning.

-- 
 http://www.eca.cx
 Audio software for Linux!

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