Messages in this thread | | | From | Ian Campbell <> | Date | Wed, 06 Jul 2011 10:25:38 +0100 | Subject | Re: [Q x86-64] on kernel_eflags |
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On Tue, 2011-07-05 at 10:47 -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.
FWIW the variable in this particular case isn't actually marked as __read_mostly...
Ian. -- Ian Campbell
* Simunye is on a oc3->oc12 simmy: bite me. :) daemon: okay :)
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