Re: Feedback on preemptible kernel patch

Dieter Nützel
2001-09-20T06:40:54Z

Am Mittwoch, 19. September 2001 01:31 schrieb Robert Love:
> On Tue, 2001-09-18 at 14:18, Roger Larsson wrote:
> > Do you run with the playback process reniced -N?
> > It should really run with a low SCHED_FIFO or SCHED_RT policy.
> > But renicing it with a negative value gives some of the benefits...
> > (but you need to run as root)
> > In addition to this the program might need to lock its pages down - the
> > only thing I can think of that could cause several seconds delay would
> > be if it has been swapped out...
>
> Certainly giving it a higher priority should improve results (especially
> with preemption), but the application should receive a fair amount of
> process attention as it is, as it is TASK_RUNNABLE at all times and the
> disk I/O should be routinely preempted. I am interested how much
> renicing it helps, though.

Nearly zero :-)

> Now, if it has to swap pages, that is a very good point. I tend to
> blame this, or perhaps something with a long held lock (the audio
> driver?) for the blips.

System didn't go into swap during whole test, sorry.

> Its so hard to tell swap/VM issues now with all the VM work, sadly...:)

I point to the second;-)

-Dieter