[vlc-devel] The "optimized" memory copies

Rémi Denis-Courmont remi at remlab.net
Wed Aug 19 21:01:51 CEST 2009


I've been benchmarking vlc_memset() and vlc_memcpy() against the built-in 
GCC-4.4 memset() and memcpy(). My system is swap-free (RAM size is 
preposterously large for my usage). Measurements were done on paged page-
aligned chunks of 256 megabytes each, against the thread time clock. CPU is a 
single Intel Pentium 4/HT.

It turns out that vlc_memset() was about 2% slower than plain memset()... so I 
kinda wonder why we bother with implementing it.

But then, vlc_memcpy() was an outrageous 35% slower than plain memcpy() on no-
first pass, and 200% (three times, yes!) slower on the first pass. Sorry but 

Rémi Denis-Courmont

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