Re: [Q x86-64] on kernel_eflags

[H. Peter Anvin]

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

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/