Re: [PATCH] powerpc64: strrchr optimization for power8

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

On 02/20/2017 09:36 PM, Carlos O'Donell wrote:
> On 02/20/2017 11:01 AM, Rajalakshmi Srinivasaraghavan wrote:
> > On 02/20/2017 07:12 PM, Carlos O'Donell wrote:
> > > On 02/14/2017 06:05 AM, Rajalakshmi Srinivasaraghavan wrote:
> > > > P7 code is used for <=32B strings and for > 32B vectorized loops are used.
> > > > This shows as an average 25% improvement depending on the position of search
> > > > character.  The performance is same for shorter strings.
> > > > Tested on ppc64 and ppc64le.
> > > What did you use to test the 25% improvement?
> > This improvement is seen when compared to power7. Benchtest is
> > modified to use length from 0 to 400  to find the average for
> > different lengths.
> Could you post your modifications for review an explain your
> process in a little more detail. I'm curious about the changes
> you made.

I modified benchtest/bench-strrchr.c to measure only the following loop
and commented the existing 'for' loops.

  for (i = 0; i < 400; ++i)
    {
      do_test (0, i, i + 1, 0, SMALL_CHAR);
      do_test (i, i, i + 1, 0, BIG_CHAR);
    }

Then the benchtests generated is copied to a spreadsheet to
calculate the improvement.

Attached is the benchtests result for ppc64le.
Note: The numbers vary slightly from run to run. 	

--
Thanks
Rajalakshmi S

Attachment: bench-result
Description: Text document