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xen-devel
Re: [Xen-devel] [PATCH] x86: don't map more than the allocated spacefor
>>> Keir Fraser <keir.fraser@xxxxxxxxxxxxx> 20.05.09 15:56 >>>
>On 20/05/2009 06:28, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:
>
>> Also, make frame_table a 'mostly read' variable. Actually, I don't
>> really understand why this has to be a variable on x86 at all -
>> address calculations involving it could be cheaper if this was just
>> a #define. Perhaps kexec is the only thing that needs this to be a
>> variable, but if that indeed is the only reason, kexec should define
>> its own static variable.
>
>Would it really be much cheaper? Pointer load versus a 64-bit constant? If
>you're sure it would be an improvement I would take a patch.
Certainly not much (especially with it now sitting in __read_mostly), but the
official latencies are still <= 1 vs >= 2, and additionally memory clobbers
wouldn't matter anymore for the compiler's scheduling decisions.
Since I wasn't sure, I didn't submit a patch right away...
Jan
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