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SubjectRe: [Q x86-64] on kernel_eflags
On Tue, Jul 05, 2011 at 10:47:10AM -0700, H. Peter Anvin wrote:
> On 07/05/2011 03:47 AM, Cyrill Gorcunov wrote:
> >
> > Should not every cpu has own copy of kernel_eflags? Just
> > to be consistent in style? Or this would be space waisting
> > and an optimization is done here?
> >
>
> Not specific to this particular case, but in general: a shared variable
> that used often but rarely written to will automatically replicate
> itself in the caches of multiple processors. This is the purpose of the
> read_mostly segment (writes are permitted but expected to be rare),
> which exists to make sure that a frequently written variable doesn't
> randomly end up in the cache line next to a read-mostly variable.
>
> -hpa
>

yeah, thanks peter!

Cyrill


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