Re: [PATCH] cfq + io priorities

[Pavel Machek <pavel@suse.cz>]

Hi!

> > OK, I ask THE question : why not using the normal nice level, via
> > current->static_prio ?
> > This way, cdrecord would be RT even in IO, and nice -19 updatedb would have
> > a minimal impact on the system.
> 
> I don't want to tie io prioritites to cpu priorities, that's a design
> decision.

OTOH it might make sense to make "nice" command set
both by default.

> > > these end values are "special" - 0 means the process is only allowed to
> > > do io if the disk is idle, and 20 means the process io is considered
> > 
> > So a process with ioprio == 0 can be forever starved. As it's not
> 
> Yes

If semaphore is held over disk io somewhere (quota code? journaling?)
you have ugly possibility of priority inversion there.

> > Thanks for making something I have been dreaming of for a long time :)
> 
> Me too :)

Yep, another thanx from me...
-- 
				Pavel
Written on sharp zaurus, because my Velo1 broke. If you have Velo you don't need...