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Re: [PATCH] powerpc: strstr optimization
- From: "Carlos O'Donell" <carlos at redhat dot com>
- To: munroesj at linux dot vnet dot ibm dot com
- Cc: OndÅej BÃlka <neleai at seznam dot cz>, Rajalakshmi Srinivasaraghavan <raji at linux dot vnet dot ibm dot com>, libc-alpha at sourceware dot org, sjmunroe at us dot ibm dot com
- Date: Thu, 21 May 2015 11:58:16 -0400
- Subject: Re: [PATCH] powerpc: strstr optimization
- Authentication-results: sourceware.org; auth=none
- References: <1429254584-124997-1-git-send-email-raji at linux dot vnet dot ibm dot com> <20150501120510 dot GB2203 at domone> <554704A1 dot 3010007 at linux dot vnet dot ibm dot com> <20150505211414 dot GA18085 at domone> <554A1703 dot 5090707 at linux dot vnet dot ibm dot com> <20150512084906 dot GA25772 at domone> <555DF4E2 dot 3040503 at redhat dot com> <1432222026 dot 16998 dot 7 dot camel at sjmunroe-ThinkPad-W500>
On 05/21/2015 11:27 AM, Steven Munroe wrote:
> On Thu, 2015-05-21 at 11:08 -0400, Carlos O'Donell wrote:
>> On 05/12/2015 04:49 AM, OndÅej BÃlka wrote:
>>>>> Following function should beat it.
>>>>>
>>>>> char *strstr (char *s, char *n)
>>>>> {
>>>>> if (n[0] == 0)
>>>>> return s;
>>>>> while (s = strchr (s, n[0]))
>>>>> {
>>>>> long i;
>>>>> for (i=1; n[i] && n[i] == s[i]; i++);
>>>>> if (n[i] == 0)
>>>>> return s;
>>>>> s++;
>>>>> }
>>>>> }
>>>> Calling strchr in a loop is not showing improvement when compared
>>>> to the proposed patch.
>>>>>
>>> Evidence?
>>>
>>
>> I agree with Ondrej here. What tests are you doing to show there is
>> no performance improvement? Can we see those tests? Can you contribute
>> them to the microbenchmark so other Power vendors can use them against
>> their particular hardware to validate performance?
>>
>
> I thought this was addressed with
> https://www.sourceware.org/ml/libc-alpha/2015-05/msg00276.html
>
> Which includes results from benchtest/bench-strstr.c.
>
> Why do we need another micro-benchmark for this?
You don't. The above addresses my complaints. I must have missed
the other post upthread.
Cheers,
Carlos.