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Re: [PATCH] powerpc: strcasestr optimization
- From: Steven Munroe <munroesj at linux dot vnet dot ibm dot com>
- To: OndÅej BÃlka <neleai at seznam dot cz>
- Cc: Rajalakshmi Srinivasaraghavan <raji at linux dot vnet dot ibm dot com>, GNU C Library <libc-alpha at sourceware dot org>, Steve Munroe <sjmunroe at us dot ibm dot com>
- Date: Mon, 01 Jun 2015 09:36:47 -0500
- Subject: Re: [PATCH] powerpc: strcasestr optimization
- Authentication-results: sourceware.org; auth=none
- References: <55687597 dot 1060101 at linux dot vnet dot ibm dot com> <556C36D8 dot 2070208 at linux dot vnet dot ibm dot com> <20150601122830 dot GA14649 at domone>
- Reply-to: munroesj at linux dot vnet dot ibm dot com
On Mon, 2015-06-01 at 14:28 +0200, OndÅej BÃlka wrote:
> On Mon, Jun 01, 2015 at 04:11:28PM +0530, Rajalakshmi Srinivasaraghavan wrote:
> >
> > This patch optimizes strcasestr function for power >= 7 systems.
> > This patch uses optimized strlen and strnlen for calculating
> > string length and the average improvement of this optimization is ~40%.
> > This patch is tested on powerpc64 and powerpc64le.
> > Attached the benchresults with this new patch.
> >
> Thats not enough. As strcasestr that I submited is around three times
> slower your implementation would likely be regression over generic one.
>
> A problem here is that you use moronic algorithm. Fix algorithm first
> before trying to optimize it.
>
This is not very helpful. You are demanding changes without clear
explanation and justification.
What is wrong with Raja's algorithm? What is insufficient in the
benchmark data she has provided? And why do you think your specific
design applies to PowerISA and POWER7/POWER8 micro-architecture.
What data do you have that justified this objection?