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Subject: Re: [patch] voluntary-preempt-2.6.8-rc3-O5
From: Lee Revell <rlrevell@joe-job.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Florian Schmidt <mista.tapas@gmx.net>,
       linux-kernel <linux-kernel@vger.kernel.org>,
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On Thu, 2004-08-12 at 20:04, Lee Revell wrote:

> So, it seems that if a SCHED_FIFO process opens a PCM device using mmap, 
> then mlockall's the memory, then another process mlockall's memory, the 
> result is an xrun 100% of the time.
> 

I have found that around 1400 KB is a magic number on my system, this
triggers the preempt violation/xrun about 50% of the time.  1300 never
triggers it, 1500 always triggers it.

Also the amount of memory being mlockall'ed does not affect the length
of the preemption violation - if we hit it at all, there's a 10ms
latency, whether we lock 1400KB or 100MB.

Hopefully O6 will give enough info to track this down.

Lee