Subject: Re: [linux-audio-dev] State of kernel?
From: Benno Senoner (sbenno_AT_gardena.net)
Date: Fri Oct 13 2000 - 04:38:58 EEST
On Tue, 10 Oct 2000, Roger Larsson wrote:
>
> Conclusion: finer grained locking will improve both SMP performance for
> computers with lots of processors and make low latency kernels possible.
> Note: you need to add an extra check for if scheduling is required when
> you leave a lock - some do not want this overhead and the kernel will
> probably end up with several compilation options.
>
> SMP / UP
> standard / preemtive
>
> with the combinations of SMP-standard, UP-preemtive, UP-standard being
> the most common.
Roger, does SMP-preemptive make sense ?
what if one wants low latencies on a SMP box ?
Will SMP-standard be enough ?
I mean: assume you have 2 CPUs:
there are 3 threads running, two of them holding a lock, and
a third SCHED_FIFO thread (the famous audio thread with 1msec fragments), which
wants to be scheduled, but is unable to do so, because both CPUs must "wait"
until the next lock release.
Am I saying nonsense ?
Can you explain the behaviour ?
Plus I would be interesed in an analogous case ( dual CPU box) where
there are two threads holding a lonck and two audio threads running (assume
we have two soundcards in our box and each audio thread outputs the data on a
separate soundcard with small buffersizes)
thanks for infos,
Benno.
>
>
> /RogerL
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