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Re: [PATCH] Simplify strncat.
- From: Adhemerval Zanella <azanella at linux dot vnet dot ibm dot com>
- To: libc-alpha at sourceware dot org
- Date: Wed, 17 Dec 2014 16:31:25 -0200
- Subject: Re: [PATCH] Simplify strncat.
- Authentication-results: sourceware.org; auth=none
- References: <20141216202438 dot GA5612 at domone> <20141216203638 dot D237C2C2448 at topped-with-meat dot com> <20141217163206 dot GA26604 at domone>
On 17-12-2014 14:32, OndÅej BÃlka wrote:
> On Tue, Dec 16, 2014 at 12:36:38PM -0800, Roland McGrath wrote:
>> Use '\0', not '\000'.
>> IIRC we have a general policy about having a benchtests case and citing
>> numbers on that.
> That is not policy as benchtest results on string function are still
> meaningless. Here I could simply improve benchtest score by inlining
> strnlen and memcpy implementations, for example with
> #define memcpy memcpy2
> #include <string/memcpy.c>
> As it avoids call overhead. However it would be big mistake to do that
> "optimization" as strncat is cold function while memcpy is likely in
> memory it degrade performance due to additonal icache misses.
This is a fair criticize, but benchtests from string functions are far for
'meanigless'. On powerpc side, for instance, I noted unaligned cases
that current code for strcpy was outperforming. It leads to check more
result using different workloads and profiler and code a better strategy.
Which resulted in a better implementation in the end (patch just posted).
Better would be to characterize a better string benchtest and provide