Re: [Xen-devel] [PATCH] xen/credit2: Drop unnecessary bit test

[Dario Faggioli <dfaggioli@xxxxxxxx>]

On Thu, 2018-01-11 at 17:36 +0000, Andrew Cooper wrote:
> It is generally worth doing a read to conditionally avoid a locked
> RMW,
> in the case that you expect the locked RMW to be unnecessary (i.e.
> the
> modification is already present).
> 
> The same is not true for plain memory reads and writes.  The overhead
> of
> the conditional jump far outweighs the saving of possibly not
> dirtying
> the cache line.
> 
Sure.

> The reason I noticed this is because (with my bitops change), the
> compiler optimised the if out entirely.
> 
Ah, interesting. :-)

It's not necessary, as George Acked it already, but feel free to add a:

Reviewed-by: Dario Faggioli <dfaggioli@xxxxxxxx>

Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
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Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Software Engineer @ SUSE https://www.suse.com/

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