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SubjectRe: [PATCH 2/2] x86/asm/entry/32: Remove unnecessary optimization in stub32_clone
On 04/22/2015 07:10 PM, Josh Triplett wrote:
> On Wed, Apr 22, 2015 at 09:54:24AM -0700, Andy Lutomirski wrote:
>> On Wed, Apr 22, 2015 at 9:40 AM, Denys Vlasenko <dvlasenk@redhat.com> wrote:
>>> Really swap arguments #4 and #5 in stub32_clone instead of "optimizing"
>>> it into a move.
>>>
>>> Yes, tls_val is currently unused. Yes, on some CPUs XCHG is a little bit
>>> more expensive than MOV. But a cycle or two on an expensive syscall like
>>> clone() is way below noise floor, and obfuscation of logic introduced
>>> by this optimization is simply not worth it.
>>
>> Ditto re: Josh's patch.
>
> I do think my two-patch HAVE_COPY_THREAD_TLS series should go in fixing
> this, but I'd like to see the final version of Denys' comment added on
> top of it (with an update to the type and name of the tls argument to
> match the changes to sys_clone).
>
> Denys, would you consider submitting a patch adding your comment on top
> of the two-patch series I just sent?

Okay.



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