Re: [PATCH 1/2] Make the batch size of the percpu_counterconfigurable

[Tim Chen]

On Tue, 2013-04-30 at 11:10 -0700, Eric Dumazet wrote:
> On Tue, 2013-04-30 at 09:23 -0700, Tim Chen wrote:
> > On Tue, 2013-04-30 at 13:32 +0000, Christoph Lameter wrote:
> > > On Mon, 29 Apr 2013, Tim Chen wrote:
> > > 
> > > > diff --git a/include/linux/percpu_counter.h b/include/linux/percpu_counter.h
> > > > index d5dd465..5ca7df5 100644
> > > > --- a/include/linux/percpu_counter.h
> > > > +++ b/include/linux/percpu_counter.h
> > > > @@ -22,6 +22,7 @@ struct percpu_counter {
> > > >  	struct list_head list;	/* All percpu_counters are on a list */
> > > >  #endif
> > > >  	s32 __percpu *counters;
> > > > +	int *batch ____cacheline_aligned_in_smp;
> > > >  };
> > > 
> > > What is this for and why does it have that alignmend?
> > 
> > I was assuming that if batch is frequently referenced, it probably
> > should not share a cache line with the counters field.
> 
> But 'counters' field has the same requirement. Its supposed to be read
> only field. 
> 
> So please remove this '____cacheline_aligned_in_smp', as it makes the
> whole struct percpu_counter at least two cache lines wide, for no
> obvious reason.
> 

Will do.

Thanks.

Tim

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