[Ffmpeg-cvslog] CVS: ffmpeg/libavcodec mpegvideo.c,1.511,1.512

[Loren Merritt]

On Thu, 23 Mar 2006, Jeff Clagg wrote:
>
> I tried on one machine (not my own) and got mixed results, mostly
> unfavorable.
>
> The machine is a dual core 3.2ghz p4. I compared cvs from 3-21 (just
> prior to Loren's last bunch of mmx commits) with cvs from after the
> prefetch change, using GCC 4.0.3. In a nutshell, mpeg4 ASP is about 8%
> slower, mpeg2 is 10%-20% slower, but H.264 speed improved by less than
> 2%.

If it turns out to be P4 vs Athlon, I blame the P4's pitiful L1 cache. 
Maybe prefetching the next block evicts the current block... 
Try fetching to L2 only (patch).

--Loren Merritt
-------------- next part --------------
Index: i386/dsputil_mmx.c
===================================================================
RCS file: /cvsroot/ffmpeg/ffmpeg/libavcodec/i386/dsputil_mmx.c,v
retrieving revision 1.118
diff -u -r1.118 dsputil_mmx.c
--- i386/dsputil_mmx.c	23 Mar 2006 20:16:36 -0000	1.118
+++ i386/dsputil_mmx.c	24 Mar 2006 10:02:50 -0000
@@ -2497,7 +2497,7 @@
         p+= stride;\
     }while(--h);\
 }
-PREFETCH(prefetch_mmx2,  prefetcht0)
+PREFETCH(prefetch_mmx2,  prefetcht1)
 PREFETCH(prefetch_3dnow, prefetch)
 #undef PREFETCH