Re: Memory allocation and the "prealloc" procfile

[Takashi Iwai <tiwai@suse.de>]

At Mon, 04 Apr 2005 10:03:37 +0100,
Andy Robinson wrote:
> 
> I'm using Mandrake 10.1 on a DELL Precision M60.
> Soundcard is Intel 82801DB-ICH4
> ALSA version 1.0.6
> 
> By default, /proc/asound/card0/pcm0p/sub0/prealloc contains the number
> 64 and SNDCTL_DSP_GETOSPACE reports a total of 16k bytes output space
> available. If I
> echo 128 >/proc/asound/card0/pcm0p/sub0/prealloc
> then SNDCTL_DSP_GETOSPACE reports a total of 32k bytes.
> 
> My question is, what is the rest of the "prealloc" memory being used
> for? And how can I change the amounts used for whatever other purposes,
> so as to get a bigger SNDCTL_DSP_GETOSPACE buffer? It's not such a
> problem for me but one of my users reports that with a 128k "prealloc",
> he still gets only 4k from SNDCTL_DSP_GETOSPACE. Is it perhaps an ALSA
> version issue?

It might be.  It's worth to try the latest ALSA version, anyway.

If you want a bigger buffer, you can call SNDCTL_DSP_SETFRAGMENT ioctl
to specify the fragments and its size explicitly.


Takashi


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