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

[Tetsuji \"Maverick\" Rai]

I've done a temporary minor hacking, which tells kernel only the half
value of nice in all processes.  Actually idle percentage was lowered,
but the response of the main application became slower (as a matter of
course.)

I'm not sure which is better..if possible I want to take advantages of
each one :)   Am I expecting too much?

regards,
---------------------my minor hacking--------------
maverick:/usr/src/linux/kernel% diff sched.c sched.c.orig
57d56
< /*
61,68d59
< */
< /*
<  * hacked by Tetsuji Maverick Rai
<  */
< #define NICE_TO_PRIO(nice)    (MAX_RT_PRIO + (nice/2) + 20)
< #define PRIO_TO_NICE(prio)    (((prio) - MAX_RT_PRIO - 20)*2)
< #define TASK_NICE(p)          PRIO_TO_NICE((p)->static_prio)
<
--------------------


On 5/19/05, Tetsuji Maverick Rai <tetsuji.rai@xxxxxxxxx> wrote:
> 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
> >
> 
-- 
Luckiest in the world / Weapon of Mass Distraction
http://maverick6664.bravehost.com/
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