Re: [PATCH] Optimize prefixcmp()

From: René Scharfe <rene.scharfe@lsrfire.ath.cx>
Date: Jan 3, 2008, 00:45 UTC
Message-ID: <477C301A.9020001@lsrfire.ath.cx>
In-Reply-To: <7v1w90xdpe.fsf@gitster.siamese.dyndns.org>

Junio C Hamano schrieb:

Show 18 quoted lines

> René Scharfe <rene.scharfe@lsrfire.ath.cx> writes:
> 
>> prefixcmp() was already optimized before -- only for a different use
>> case.  At a number of callsites the prefix is a string literal, which
>> allowed the compiler to perform the strlen() call at compile time.
>>
>> The patch increases the text size considerably: the file "git" is
>> 2,620,938 without and 2,640,450 with the patch in my build (there are
>> 136 callsites in builtin*.c).  The new version of prefixcmp() shouldn't
>> be inlined any more, as the benefit of doing so is gone.
> 
> Yuck, you are absolutely right.  The late thread may have been
> well intentioned but resulted in this regression.  Sorry about
> that.
> 
> I presume that all callers with constant prefix are outside
> performance critical parts?  Can we simply uninline the function
> in that case?

Most of them seem to be non-critical performance-wise. They are part of code to parse parameters or config files. Exceptions are the commit message parsing code used for --pretty=format (which can't be an issue given that prefixcmp() was made the way it's now to speed up this code path) and half of the callsites in fast-import.c.

René