From 8f2b21a80f80eb76b93be5bb96eb2ff113ae3c49 Mon Sep 17 00:00:00 2001 From: Michael Niedermayer Date: Sun, 15 Sep 2002 10:02:15 +0000 Subject: [PATCH] fixing memalign Originally committed as revision 949 to svn://svn.ffmpeg.org/ffmpeg/trunk --- libavcodec/mem.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/libavcodec/mem.c b/libavcodec/mem.c index 113e285..5799c07 100644 --- a/libavcodec/mem.c +++ b/libavcodec/mem.c @@ -29,8 +29,8 @@ void *av_malloc(int size) { void *ptr; -#if defined ( ARCH_X86 ) && defined ( HAVE_MEMALIGN ) && 0 - ptr = memalign(64,size); +#if defined (HAVE_MEMALIGN) + ptr = memalign(16,size); /* Why 64? Indeed, we should align it: on 4 for 386 @@ -40,11 +40,29 @@ void *av_malloc(int size) Because L1 and L2 caches are aligned on those values. But I don't want to code such logic here! */ + /* Why 16? + because some cpus need alignment, for example SSE2 on P4, & most RISC cpus + it will just trigger an exception and the unaligned load will be done in the + exception handler or it will just segfault (SSE2 on P4) + Why not larger? because i didnt see a difference in benchmarks ... + */ + /* benchmarks with p3 + memalign(64)+1 3071,3051,3032 + memalign(64)+2 3051,3032,3041 + memalign(64)+4 2911,2896,2915 + memalign(64)+8 2545,2554,2550 + memalign(64)+16 2543,2572,2563 + memalign(64)+32 2546,2545,2571 + memalign(64)+64 2570,2533,2558 + + btw, malloc seems to do 8 byte alignment by default here + */ #else ptr = malloc(size); #endif if (!ptr) return NULL; +//fprintf(stderr, "%X %d\n", (int)ptr, size); /* NOTE: this memset should not be present */ memset(ptr, 0, size); return ptr; -- 2.7.4