Re: [PATCH] cpuacct: VIRT_CPU_ACCOUNTING don't prevent percpu cputime count

[Bharata B Rao <bharata@linux.vnet.ibm.com>]

On Wed, Apr 29, 2009 at 03:38:54AM +0530, Balbir Singh wrote:
> * KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> [2009-04-28 15:53:32]:
> > 
> >  	do {
> > -		percpu_counter_add(&ca->cpustat[idx], val);
> > +		__percpu_counter_add(&ca->cpustat[idx], val, cpuacct_batch);
> 
> This will make the end result very off the real value due to large
> batch value per cpu. If we are going to go this route, we should
> probably consider using __percpu_counter_sum so that the batch value
> does not show data that is way off.

But __percpu_counter_sum takes fbc->lock spinlock and that is the cause of
the problem Kosaki mentions I believe.

Regards,
Bharata.