On Thu, 20 Feb 2003, Abramo Bagnara wrote:
> Now I'm able to get the same results you see.
>
> However I think that we need to extract some results from this data.
>
> I'll leave alone MMX optimizations because I want to compare apples with
> apples.
>
> The distributed saturation (also when it's missing the check/repeat
> concurrency correctness part) costs more than 4 times the ticks needed
> for a (fully correct wrt concurrency) saturate once approach for the
> case 2048 8 32768.
>
> CPU clock: 1460477150.884593
> mix_areas0: 86747 0.031975%
> mix_areas1: 259424 0.095623% (0)
> mix_areas1_mmx: 253894 0.093585% (0)
> mix_areas2: 132321 0.048773% (365)
> mix_areas3: 332411 0.122526% (0)
>
> The server based approach has an added cost of an extra context switch
> every period (about 1500 cycles on my machine i.e.), but this is fully
> amortized by such an huge difference.
>
> What's your opinion?
Interesting is that my Intel P3 CPU has slightly different times:
pnote:/home/perex/alsa/alsa-lib/test # ./code 2048 8 32768
Scheduler set to Round Robin with priority 99...
CPU clock: 847.292487Mhz (UP)
Summary (the best times):
mix_areas_srv : 576382 0.366206%
mix_areas0 : 556852 0.353798%
mix_areas1 : 867989 0.551480%
mix_areas1_mmx: 625144 0.397187%
mix_areas2 : 903335 0.573937%
areas1/srv ratio : 1.505927
areas1_mmx/srv ratio : 1.084600
I think that we can lose more in the client/server model. Also, note that
we can use even futexes (if there's a hope that the possible context
switch is acceptable) and then we can remove the cmpxchg trick and
write-retry trick and use MMX for parallel saturation of two samples (this
last can be used in the client/server model, too, indeed).
Jaroslav
-----
Jaroslav Kysela <[EMAIL PROTECTED]>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs
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