Re: [PATCH] PowerPC:strrchr() optimization

[Rajalakshmi Srinivasaraghavan <raji at linux dot vnet dot ibm dot com>]

On 02/12/2014 11:04 PM, OndÅej BÃlka wrote:
> On Mon, Feb 10, 2014 at 11:43:09AM +0530, Rajalakshmi Srinivasaraghavan wrote:
> > Hi All
> >
> > This patch optimizes strrchr() for ppc64. I have attached the benchtest
> > output to show the performance improvement.This is coded with strchr.S as reference and uses
> > cmpb instruction for speed improvement.
> Hi,
>
> There is one thing to check as strrchr could be genericaly implemented
> by other primitives.
>
> I send a patch for that, could you check how does that compare?
>
> https://sourceware.org/ml/libc-alpha/2013-10/msg00201.html
>
> Benchmarking strrchr is bit tricky as performance depends on frequency
> of searched character. I did profiling and most common usecase is
> finding trailing / in pathnames. Typically a result is between 10 and 20
> characters from start. See following for more statistic.
>
> http://kam.mff.cuni.cz/~ondra/benchmark_string/i7_ivy_bridge/strrchr_profile/results_gcc/result.html

Hi

I have applied your changes in strrchr.c and  modified the benchtest to 
search '/' character (with more than one occurances in various positions).
Proposed ppc64 optimization is still running better than default. I have 
attached the results.

--
Thanks
Raji

Attachment: strrchr_results.txt
Description: Text document