Re: low priority soft RT?

Rik van Riel (riel@nl.linux.org)
Mon, 26 Jul 1999 22:40:25 +0200 (CEST)


On Mon, 26 Jul 1999, Stephen C. Tweedie wrote:
> On Sat, 24 Jul 1999 14:15:39 +0200 (CEST), Rik van Riel
> <riel@nl.linux.org> said:
>
> > Promotion to a higher scheduling class shouldn't be too
> > difficult.
>
> Sure, but when, exactly, will you do this? The condition I saw in
> your latest SCHED_IDLE patches are insufficient for the long term.
> Testing the lock_depth is not good enough: there are large parts
> of the VFS which now run without the kernel spinlock, but which
> can still hold or block on other resources (eg. page locks).

I completely agree on this one. We should probably mark a process
with "bonus" if another process tries to grab a lock that's held
by the first process.

It should involve no more than a little bit of code added to
the _slow_ patch -- keeping clean the fast path...

In the meantime, SCHED_IDLE should be controllable by root
(sysctl) as it is in my patch. It's a useful feature and
everybody should be able to make a decision about the risks
involved themselves (you can even start selected processes
under SCHED_IDLE and then disable it again).

Rik -- Open Source: you deserve to be in control of your data.
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