Re: [PATCH] mm/memcg: add unlikely to mercg->move_charge_at_immigrate

[Kamezawa Hiroyuki]

(2012/06/18 22:19), Wanpeng Li wrote:
> On Mon, Jun 18, 2012 at 05:09:36PM +0400, Glauber Costa wrote:
> > On 06/18/2012 05:10 PM, Wanpeng Li wrote:
> > > From: Wanpeng Li<liwp@xxxxxxxxxxxxxxxxxx>
> > >
> > > move_charge_at_immigrate feature is disabled by default. Charges
> > > are moved only when you move mm->owner and it also add additional
> > > overhead.
> >
> > How big is this overhead?
> >
> > That's hardly a fast path. And if it happens to matter, it will be
> > just bigger when you enable it, and the compiler start giving the
> > wrong hints to the code.
>
> Thank you for your quick response.
>
> Oh, Maybe I should just write comments "move_charge_at_immigrate feature
> is disabled by default. So add "unlikely", in order to compiler can optimize."

This doesn't affect the performance. likely/unlikely which doesn't affect
performance is never welcomed.

Thanks,
-Kame

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