Re: HT scheduler: is it really correct? or is it feature of HT?

[Tetsuji \"Maverick\" Rai]

But I would like a kernel to let boinc (the "nice=19" processes) fill
the idle time as much as possible.  The current kernel scheduler seems
very sensitive to low-nice (higher priority) processes.

How can I change this sensitivity?   I'm looking at kernel/sched.c,
but it's more complicated than a few years ago when I hacked this
before :) and that I'm using HT (SMP)..  Will you tell me any hint
where to modify, and/or what to take care of?  or any pointer to
proper resources on the Internet?

When I use gnome desktop with a system monitor applet, I see there's
always some idle part and top also shows the idle time on gnome even
if I don't run any specific applications besides system daemons and
gnome background processes.  However without gnome/X window, top shows
no or very small idle power (as a matter of course.)  So I want the
kernel to be less sensitive.  Maybe it will utilize more cpu power.

best regards,

On 5/19/05, Con Kolivas <kernel@xxxxxxxxxxx> wrote:
> On Thu, 19 May 2005 04:58 pm, Tetsuji "Maverick" Rai wrote:
> > On 5/19/05, Con Kolivas <kernel@xxxxxxxxxxx> wrote:
> > > ------------snip---------------
> > > Hyperthread sibling cpus share cpu power. If you let a nice 19 task run
> > > full power on the sibling cpu of a nice 0 task it will drain performance
> > > from the nice 0 task and make it run approximately 40% slower. The only
> > > way around this is to temporarily make the sibling run idle so that a
> > > nice 0 task gets the appropriate proportion of cpu resources compared to
> > > a nice 19 task. It is intentional and quite unique to the linux cpu
> > > scheduler as far as I can tell. On any other scheduler or OS a nice 19
> > > "background" task will make your machine run much slower.
> > >
> > Thanks.   I understood it's a feature of linux kernel and am satisfied
> > with it.  Actually on Windows xp my application sometimes slows down
> > maybe due to inpropoer scheduler.
> 
> Well I invented it so it's very unlikely that Windows* will have it (?yet) :D
> 
> Cheers,
> Con
> 


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