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

[Jack O'Quin]

Werner Almesberger <wa@xxxxxxxxxxxxxxx> writes:

> [ Cc:s trimmed, added abiss-general ]
>
> Con Kolivas wrote:
>> Possibly reiserfs journal related. That has larger non-preemptible code 
>> sections.
>
> If I understand your workload right, it should consist mainly of
> computation, networking (?), and disk reads.

The jack_test3.2 is basically a multiprocess realtime audio test.  A
fair amount of computation, signifcant task switch overhead, but
most I/O is to the sound card.

There's some disk activity starting clients and probably some other
system activity in the background.

> I don't know much about ReiserFS, but in some experiments with ext3,
> using ABISS, we found that a reader application competing with best
> effort readers would experience worst-case delays of dozens of
> milliseconds.
>
> They were caused by journaled atime updates. Mounting the file
> system with "noatime" reduced delays to a few hundred microseconds
> (still worst-case).

Interesting. Worth a try to verify.  Con was seeing a 6msec delay
every 20 seconds.  This was devastating to the test, which tries to
run a full realtime audio cycle every 1.45msec.
-- 
  joq
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/