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Re: [lkp] [x86/build] b2c51106c75: -18.1% will-it-scale.per_process_ops

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  Re: [lkp] [x86/build] b2c51106c75: -18.1%  will-it-scale.per_process_ops Ingo Molnar <mingo@kernel.org> - 2015-08-05 10:40 +0200
    Re: [lkp] [x86/build] b2c51106c75: -18.1% will-it-scale.per_process_ops Andy Lutomirski <luto@amacapital.net> - 2015-08-10 22:50 +0200

#1200531 — Re: [lkp] [x86/build] b2c51106c75: -18.1% will-it-scale.per_process_ops

* kernel test robot <ying.huang@intel.com> wrote:

> FYI, we noticed the below changes on
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/asm
> commit b2c51106c7581866c37ffc77c5d739f3d4b7cbc9 ("x86/build: Fix detection of GCC -mpreferred-stack-boundary support")

Does the performance regression go away reproducibly if you do:

   git revert b2c51106c7581866c37ffc77c5d739f3d4b7cbc9

?

Thanks,

	Ingo
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#1204545 — Re: [lkp] [x86/build] b2c51106c75: -18.1% will-it-scale.per_process_ops

On Wed, Aug 5, 2015 at 1:38 AM, Ingo Molnar <mingo@kernel.org> wrote:
>
> * kernel test robot <ying.huang@intel.com> wrote:
>
>> FYI, we noticed the below changes on
>>
>> git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/asm
>> commit b2c51106c7581866c37ffc77c5d739f3d4b7cbc9 ("x86/build: Fix detection of GCC -mpreferred-stack-boundary support")
>
> Does the performance regression go away reproducibly if you do:
>
>    git revert b2c51106c7581866c37ffc77c5d739f3d4b7cbc9
>
> ?

FWIW, I spot-checked the generated code.  All I saw were the deletion
of some dummy subtraction from rsp to align the stack for children,
changes of stack frame offsets, and a couple instances in which
instructions got reordered.

--Andy
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