Re: [patch] CFS scheduler, v3

On Tue, 24 Apr 2007, Siddha, Suresh B wrote:

> On Tue, Apr 24, 2007 at 10:47:45AM -0700, Christoph Lameter wrote:
> > On Tue, 24 Apr 2007, Siddha, Suresh B wrote:
> > > Anyhow, this is a straight forward optimization and needs to be done. Do you
> > > have any specific concerns?
> > 
> > Yes there should not be contention on per cpu data in principle. The 
> > point of per cpu data is for the cpu to have access to contention free 
> > cachelines.
> > 
> > If the data is contented then it should be moved out of per cpu data and properly 
> > placed to minimize contention. Otherwise we will get into cacheline 
> > aliases (__read_mostly in per cpu??) etc etc in the per cpu areas.
> 
> yes, we were planning to move this to a different percpu section, where
> all the elements in this new section will be cacheline aligned(both
> at the start, aswell as end)

I would not call this a per cpu area. It is used by multiple cpus it 
seems. But for 0.5%? on what benchmark? Is is really worth it?

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