On Wed, 2008-01-23 at 13:18 +0100, Michel Dänzer wrote:
> On Tue, 2008-01-22 at 15:56 +0100, Michel Dänzer wrote:
> > On Fri, 2008-01-18 at 13:34 +0100, Michel Dänzer wrote:
> > > This is on a PowerBook5,8.
> > >
> > > In a nutshell, things seem more sluggish in general than with 2.6.23.
> > > But in particular, processes running at nice levels >0 can get most of
> > > the CPU cycles available, slowing down processes running at nice level
> > > 0.
> >
> > The canonical test case I've come up with is to run an infinite loop
> > with
> >
> > sudo -u nobody nice -n 19 sh -c 'while true; do true; done'
> >
> > This makes my X session (X server running at nice level -1, clients at
> > 0) unusably sluggish (it can even take several seconds to process ctrl-c
> > to interrupt the infinite loop) with 2.6.24-rc but works as expected
> > with 2.6.23.
> >
> > Anybody else seeing this?
> >
> >
> > > I've seen this since .24-rc5 (the first .24-rc I tried), and it's still
> > > there with -rc8. I'd be surprised if this kind of behaviour remained
> > > unfixed for that long if it affected x86, so I presume it's powerpc
> > > specific.
> >
> > Or maybe not... I've bisected this down to the scheduler changes
> > between
> > df3d80f5a5c74168be42788364d13cf6c83c7b9c/23fd50450a34f2558070ceabb0bfebc1c9604af5
> > and b5869ce7f68b233ceb81465a7644be0d9a5f3dbb .
>
> Finished bisecting now. And the winner is...
>
> 810e95ccd58d91369191aa4ecc9e6d4a10d8d0c8 is first bad commit
> commit 810e95ccd58d91369191aa4ecc9e6d4a10d8d0c8
> Author: Peter Zijlstra <[EMAIL PROTECTED]>
> Date: Mon Oct 15 17:00:14 2007 +0200
>
> sched: another wakeup_granularity fix
>
> unit mis-match: wakeup_gran was used against a vruntime
>
> Signed-off-by: Peter Zijlstra <[EMAIL PROTECTED]>
> Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]>
>
> :040000 040000 61242d589b0082a417657807ed6329321340f7f3
> bff39e49275324e15f37d2163157733580b7df1a M kernel
>
>
> Unfortunately, I don't understand how that can cause the misbehaviour
> described above, and 2.6.24-rc8
> (667984d9e481e43a930a478c588dced98cb61fea) with the patch below still
> shows the problem. Any ideas Peter or Ingo (or anyone, really :)?
>
>
> diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
> index da7c061..a7cc22a 100644
> --- a/kernel/sched_fair.c
> +++ b/kernel/sched_fair.c
> @@ -843,7 +843,6 @@ static void check_preempt_wakeup(struct rq *rq, struct
> task_struct *p)
> struct task_struct *curr = rq->curr;
> struct cfs_rq *cfs_rq = task_cfs_rq(curr);
> struct sched_entity *se = &curr->se, *pse = &p->se;
> - unsigned long gran;
>
> if (unlikely(rt_prio(p->prio))) {
> update_rq_clock(rq);
> @@ -866,11 +865,8 @@ static void check_preempt_wakeup(struct rq *rq, struct
> task_struct *p)
> pse = parent_entity(pse);
> }
>
> - gran = sysctl_sched_wakeup_granularity;
> - if (unlikely(se->load.weight != NICE_0_LOAD))
> - gran = calc_delta_fair(gran, &se->load);
>
> - if (pse->vruntime + gran < se->vruntime)
> + if (pse->vruntime + sysctl_sched_wakeup_granularity < se->vruntime)
> resched_task(curr);
> }
>
Most curious; are you sure its not a bisection problem?
Does ppc32 (or your instance thereof) have a high resolution
sched_clock()?
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