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Date: Wed, 24 Apr 2002 08:04:03 +0300 (WET)
From: Sami Korhonen <ssakorho AT messi DOT uku DOT fi>
To: cygwin AT cygwin DOT com
Subject: 1.3.10 memcmp() bug
Message-ID: <Pine.A41.4.20.0204240757560.120142-100000@messi.uku.fi>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII

 I wasnt sure wheter I should post about this on gcc bug report list or
here. Anyways, it seems that using -O2 flag with gcc causes huge slowdown
in memcmp(). However i dont see performance drop under linux, so I suppose
it is cygwin issue.

$ gcc memtest.c -O2 -o memtest ; ./memtest.exe
Amount of memory to scan (mbytes)? 100
Memory block size (default 1024)? 1024
Allocating memory
Testing memory - read (1 byte at time)
Complete: 889.73MB/sec
Testing memory - read (4 bytes at time)
Complete: 3313.07MB/sec
Freeing memory

$ gcc memtest.c -o memtest ; ./memtest.exe
Amount of memory to scan (mbytes)? 100
Memory block size (default 1024)? 1024
Allocating memory
Testing memory - read (1 byte at time)
Complete: 2517.94MB/sec
Testing memory - read (4 bytes at time)
Complete: 2933.50MB/sec
Freeing memory


'1 byte at time' is using memcmp() to compare two blocks.


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