Re: [PATCH]sched: Isochronous class v2 for unprivileged soft rt scheduling

["Jack O'Quin" <joq@xxxxxx>]

Paul Davis <paul@xxxxxxxxxxxxxxxxxxxxx> writes:

>>That's discouraging about reiserfs.  Is it version 3 or 4?  Earlier
>>versions showed good realtime responsiveness for audio testers.  It
>>had a reputation for working much better at lower latency than ext3.
>
> over on #ardour last week, we saw appalling performance from
> reiserfs. a 120GB filesystem with 11GB of space failed to be able to
> deliver enough read/write speed to keep up with a 16 track
> session. When the filesystem was cleared to provide 36GB of space,
> things improved. The actual recording takes place using writes of
> 256kB, and no more than a few hundred MB was being written during the
> failed tests.
>
> everything i read about reiser suggests it is unsuitable for audio
> work: it is optimized around the common case of filesystems with many
> small files. the filesystems where we record audio is typically filled
> with a relatively small number of very, very large files.

I was not speaking of its disk performance, but rather of low-latency
CPU performance.  In 2.4 with the low-latency patches, reiserfs did
that fairly well.

I know its design is not focused on streaming large blocks of data to
disk.  But, when you're recording clicks every 20 seconds, disk
throughput is definitely a secondary consideration.

Looks like we need to do another study to determine which filesystem
works best for multi-track audio recording and playback.  XFS looks
promising, but only if they get the latency right.  Any experience
with that?
-- 
  joq
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