Subject: [linux-audio-dev] Re: costs of IPC
From: Abramo Bagnara (abramo_AT_alsa-project.org)
Date: Sat May 12 2001 - 11:32:20 EEST
Paul Davis wrote:
>
> Abramo wondered about how the benchmark I referenced worked:
>
> To quote from the lat_ctx man page:
>
> lat_ctx measures context switching time for any reasonable
> number of processes of any reasonable size. The processes are
> connected in a ring of Unix pipes. Each process reads a token
> from its pipe, possibly does some work, and then writes the
> token to the next process.
>
> Processes may vary in number. Smaller numbers of processes
> result in faster context switches. More than 20 processes is
> not supported.
>
> Processes may vary in size. A size of zero is the baseline
> process that does nothing except pass the token on to the next
> process. A process size of greater than zero means that the
> process does some work before passing on the token. The work is
> simulated as the summing up of an array of the specified
> size. The summing is an unrolled loop of about a 2.7 thousand
> instructions.
>
> The effect is that both the data and the instruction cache get
> polluted by some amount before the token is passed on. The data
> cache gets polluted by approximately the process ``size''. The
> instruction cache gets polluted by a constant amount,
> approximately 2.7 thousand instructions.
Paul, I'm a wrong if I affirm that the same instruction/data cache
pollution is caused by plugin/component invocation in one-process
approach?
-- Abramo Bagnara mailto:abramo_AT_alsa-project.orgOpera Unica Phone: +39.546.656023 Via Emilia Interna, 140 48014 Castel Bolognese (RA) - Italy
ALSA project http://www.alsa-project.org It sounds good!
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