Subject: Re: [PATCH V2] powerpc/irq: Enable some more exceptions in /proc/interrupts interface

From: Anshuman Khandual <[email-masked]>
Date: Mon, 13 Jul 2015 12:16:39 +0530

On 07/13/2015 11:11 AM, Michael Ellerman wrote:
> On Mon, 2015-07-13 at 10:54 +0530, Anshuman Khandual wrote:
>> On 07/10/2015 12:40 PM, Michael Neuling wrote:
>>> What's the performance impact of this?  If you run this test with --fp,
>>> --altivec or --vector what is the impact of adding this patch?
>>>
>>> http://ozlabs.org/~anton/junkcode/context_switch2.c
>>>
>>> eg 
>>>   ./context_switch2 --fp 0 0 
>>
>> Please find the results here which looks similar with or without
>> the patch being applied.
> 
> No they don't look similar with or without.
> 
>> (A) Floating point context switches (context_switch2 --fp 0 0)
> 
> If you just sort them you see:
> 
> 316478	after
> 316540	after
> 316650	after
> 318448	after
> 318904 before
> 320216 before
> 321206 before
> 321308 before
> 323460	after
> 324596 before
> 
> 
> It looks like ~1% degradation. Please run the test more times (maybe 1000) and
> see how the numbers look.

Average of 1000 iterations looks better.

With    the patch : 322599.57  (Average of 1000 results)
Without the patch : 320464.924 (Average of 1000 results)