Re: [PATCH v2 1/2] mm/slub: optimize alloc/free fastpath by removing preemption on/off

[Eric Dumazet]

On Thu, 2015-01-15 at 23:07 -0500, Steven Rostedt wrote:
> On Thu, 15 Jan 2015 21:57:58 -0600 (CST)
> Christoph Lameter <cl@xxxxxxxxx> wrote:
> 
> > > I get:
> > >
> > > 		mov    %gs:0x18(%rax),%rdx
> > >
> > > Looks to me that %gs is used.
> > 
> > %gs is used as a segment prefix. That does not add significant cycles.
> > Retrieving the content of %gs and loading it into another register
> > would be expensive in terms of cpu cycles.
> 
> OK, maybe that's what I saw in my previous benchmarks. Again, that was
> a while ago.

I made same observation about 3 years ago, on old cpus.


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