Re: [patch] voluntary-preempt-2.6.8.1-P3

Florian Schmidt
2004-08-18T12:53:23Z

On Wed, 18 Aug 2004 14:27:03 +0200
Ingo Molnar <mingo@elte.hu> wrote:

>
> * Florian Schmidt <mista.tapas@gmx.net> wrote:
>
> > Hi, it applied against 2.6.8.1 with some offsets and some buzz [?].
> > Well anyways it compiled fine and the copy_page_range latency is
> > gone.. Now i also see the extracty entropy thing, too..
>
> could you try the attached patch that changes SHA_CODE_SIZE to 3 -
> does this reduce the latency caused by extract_entropy?

will do..

>
> > Btw: one question: at one point in time the IRQ handlers were in the
> > SCHED_FIFO scheduling class. Why has this changed?
>
> so that they dont starve the audio threads by default - the audio IRQ
> has to get another priority anyway. Maybe we could try a default
> SCHED_FIFO prio lower than the typical rt_priority of jackd - e.g. 30?

Oh, upon rereading the chrt manpage i found out why i failed to set them
to SCHED_FIFO manually. So it was my error. I thought the
scheduling of the IRQ handlers was not changable at runtime. Thus my
question to make them SCHED_FIFO by default.

Well, i still think they should be SCHED_FIFO by default, so no user
process that is not itself SCHED_FIFO can starve them [X11 was able to
starve mouse irq's on my system with the defualt IRQ handlers
running SCHED_OTHER FWIW]. To make starving of user-SCHED_FIFO processes
unprobably maybe use a default static prio of 0.

Afaik jackd uses priorities > 0 for its audio threads when runing
SCHED_FIFO anyways..

But since the user will have to tweak his IRQ handlers manually anyways
[set soundcard irq higher prio than the rest, etc..], it doesn't really
make a difference.

Flo

--
Palimm Palimm!