Re: Audio skips when RAM is ~full

From: Anthony DiSante
Date: Sat Nov 01 2003 - 07:50:23 EST

Willy Tarreau wrote:
Actually, I don't scan the disk to find random albums; I have a text file that contains a list of every album's full path, and I pick a random line from that file. So only the selected album's directory gets scanned. And the mp3 partition is mounted read-only (I should have mentioned that before), so the atimes shouldn't be getting written as it is.

OK, so it's not a disk IO problem at all. It's really related to the sound
driver it seems. Now that you say it, I remember having noticed skips on
my laptop with a via 82cxxx chip after tens of minutes playing. At first
I thought it was related to other activity on the system, but it did exactly
what you describe, play seconds 1, 2, then 5 without a hole between them.
There may be a problem with the way the audio buffer gets allocated or freed.

Yeah... in my experience, the whole ac'97 deal is pretty buggy (for one thing, with both ALSA and OSS drivers, output is distorted unless I keep the volume below ~70%...). But as I said, the skipping only happens when the memory is full, or getting close to full. If I select specific albums to play instead of using my random function, I can usually play a few albums and there aren't any skips, not until the memory gets pretty full.

So I'm guessing that there isn't actually a way to manually move buffer-data out of RAM?

Yes, there is. I have a quick'n'dirty program which does exactly that.
Basically, you tell it how many kB you want to free, then it allocates
and uses that amount of memory, frees it and exits. Buffered data gets
flushed very quickly. I sometimes give it a try before starting to work
on large kernel trees, because it helps the entire directories to fit in

Here it is if you're interested. Don't start it without an argument, it
will try to allocate 4G !

4G!! (Note to self: s/ffffffff/0000ffff/...) Thanks a lot, I'll give this a try. It certainly works here on my home system.

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