Subject: [linux-audio-dev] Re: new preemptive kernel-patch from Montavista available
From: Andrew Morton (andrewm_AT_uow.edu.au)
Date: Thu Nov 23 2000 - 15:18:20 EET
Benno Senoner wrote:
>
> Hi,
> Andrew Morton informed me that Montavista has released a new
> preemptive kernel, which seems to achieve 2msec latencies when
> running latencytest. (I haven't tested it yet).
> I'm attaching Nigel's message below.
OK, I've had a quick poke through it.
It's definitely a work-in-progress. The decision to not
do any form of context switch (preemptive or cooperative) when the
"big kernel lock" is held means that it's fairly easy to get large
scheduling dropouts - I saw one of 70 milliseconds quite early
into testing.
Also the performance is down a bit - a bonnie++ benchmark run
goes from 6min13 to 6min31. A kernel compile from 6min11 to 6min45.
The patch is fairly x86-specific and doesn't address SMP.
But it's way too early to judge these things. I think MontaVista
are waiting until the filesystem guys completely remove the big lock in
the 2.5 stream.
Plus if I were them I wouldn't invest the effort of doing the SMP and
non-x86 work unless they got some sort of buy-in beforehand from
Linus (good luck...).
I don't think MontaVista are targetting this as a 2.4 kernel feature,
but I've Cc:'ed Nigel and George so they can speak for themselves.
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