On Thu, Nov 21, 2013 at 09:22:24AM -0800, Yinghai Lu wrote:
> On Thu, Nov 21, 2013 at 7:03 AM, Peter Zijlstra <pet...@infradead.org> wrote:
> >>
> >> This one seems fix NULL reference in compute_group_power.
> >>
> >> but get following on current Linus tree plus tip/sched/urgent.
> >>
> >> divide error: 0000 [#1] SMP
> >> [ 28.190477] Modules linked in:
> >> [ 28.192012] CPU: 11 PID: 484 Comm: kworker/u324:0 Not tainted
> >> 3.12.0-yh-10487-g4b94e59-dirty #2044
> >> [ 28.210488] Hardware name: Oracle Corporation Sun Fire
> >> [ 28.229877] task: ffff88ff25205140 ti: ffff88ff2520a000 task.ti:
> >> ffff88ff2520a000
> >> [ 28.236139] RIP: 0010:[<ffffffff810d9ff4>] [<ffffffff810d9ff4>]
> >> find_busiest_group+0x2b4/0x8a0
> >
> > Hurmph.. what kind of hardware is that? and is there anything funny you
> > do to make it do this?
>
> intel nehanem-ex or westmere-ex 8 sockets system.
>
> I tried without my local patches, the problem is still there.
And I suppose a kernel before
863bffc80898 ("sched/fair: Fix group power_orig computation")
work fine, eh?
I'll further assume that your RIP points to:
sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr;
indicating that sds.total_pwr := 0.
update_sd_lb_stats() computes it like:
sds->total_pwr += sgs->group_power;
which comes out of update_sg_lb_stats() like:
sgs->group_power = group->sgp->power;
Which we compute in update_group_power() similarly to how we did before
863bffc80898.
Which leaves me a bit puzzled.
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