lkml.org 
[lkml]   [2007]   [Jan]   [13]   [last100]   RSS Feed
Views: [more markup]  [less markup]  [headers]  [forward] 
 
Messages in this thread
/
DateFri, 12 Jan 2007 23:36:43 -0800
FromRavikiran G Thirumalai <>
SubjectRe: High lock spin time for zone->lru_lock under extreme conditions
On Sat, Jan 13, 2007 at 03:39:45PM +1100, Nick Piggin wrote:
> Ravikiran G Thirumalai wrote:> >Hi,> >We noticed high interrupt hold off times while running some memory 
> >intensive> >tests on a Sun x4600 8 socket 16 core x86_64 box.  We noticed softlockups,> > [...]> > >We did not use any lock debugging options and used plain old rdtsc to
> >measure cycles.  (We disable cpu freq scaling in the BIOS). All we did was
> >this:> >> >void __lockfunc _spin_lock_irq(spinlock_t *lock)> >{> >        local_irq_disable();
> >        ------------------------> rdtsc(t1);
> >        preempt_disable();
> >        spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
> >        _raw_spin_lock(lock);
> >        ------------------------> rdtsc(t2);
> >        if (lock->spin_time < (t2 - t1))
> >                lock->spin_time = t2 - t1;
> >}
> >
> >On some runs, we found that the zone->lru_lock spun for 33 seconds or more
> >while the maximal CS time was 3 seconds or so.> > What is the "CS time"?

Critical Section :).  This is the maximal time interval I measured  from 
t2 above to the time point we release the spin lock.  This is the hold 
time I guess.

> > It would be interesting to know how long the maximal lru_lock *hold* time 
> is,> which could give us a better indication of whether it is a hardware problem.
> > For example, if the maximum hold time is 10ms, that it might indicate a
> hardware fairness problem.

The maximal hold time was about 3s.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-01-13 08:31    [from the cache]
©2003-2008