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

From: Andy Lutomirski
Date: Mon Aug 10 2015 - 16:40:11 EST

On Wed, Aug 5, 2015 at 1:38 AM, Ingo Molnar <mingo@xxxxxxxxxx> wrote:
> * kernel test robot <ying.huang@xxxxxxxxx> wrote:
>> FYI, we noticed the below changes on
>> 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.

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