Re: [alsa-devel] Re: audio latencies, real-time scheduling etc.

Paul Barton-Davis (pbd@Op.Net)
Tue, 29 Jun 1999 21:49:58 -0400


[ linux-kernel folk: note the question in my first new paragraph ]

>>My tests shows that increasing the scheduling frequency to HZ=1000 ....
>
>I feel wary of increasing HZ, but maybe I'll try this out and see how
>it works for me.

First clarification: increasing HZ has big payoffs for a program like
your benchmark, which *isn't* burning CPU cycles generating audio in
real time. But it can be problematic for an application that can use
every available cycle for its own work, because the ten-fold increase
in timer interrupt frequency is going to steal cycles. Does anyone
have any idea how many (x86) cycles it takes to process a timer
interrupt that doesn't result in any change to the tasks running on
each CPU ?

>But I want audio latency to exceed the basic MIDI latency.

Second clarification: by "exceed" I meant "be better than" i.e. lower.

--p

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