Hi, The prefetching instructions are very attached with the processor cache architecture. Probably the ATOM processor has a very tiny cache and this prefetching is dirtying the cache and forcing some others loads from the main memory.
Disable all cache prefetch isn't a good idea, I think. But in some functions (bit_fiill and memcpy, I guess) we use prefetching instructions with 2 or 3 cache lines ahead. Maybe this code is affecting the performance. Unfortunately, I don't have access to any ATOM processor to make some test. Regards, André Tupinambá On Wed, Jun 9, 2010 at 11:41 AM, Soeren Sandmann <[email protected]> wrote: > Soeren Sandmann <[email protected]> writes: > >> prefetching. On an AMD Phenom with 512 KB of L2 and 512 KB of L3, >> disabling prefetch was a tiny but consistent slow-down. > > Here are the numbers from the AMD: > > Existing code, with prefetching: > > [ # ] backend test min(s) median(s) stddev. count > [ 0] image evolution 17.896 18.363 1.10% 6/6 > [ 1] image firefox-planet-gnome 25.778 26.390 1.57% 6/6 > [ 2] image firefox-talos-gfx 12.576 12.721 0.58% 6/6 > [ 3] image firefox-talos-svg 60.303 61.098 0.53% 5/6 > [ 4] image gnome-system-monitor 7.405 7.414 0.10% 6/6 > [ 5] image gnome-terminal-vim 4.147 4.162 0.28% 6/6 > [ 6] image gvim 21.949 22.175 0.52% 6/6 > [ 7] image midori-zoomed 5.656 5.714 0.70% 6/6 > [ 8] image ocitysmap 4.008 4.018 0.53% 6/6 > [ 9] image poppler 2.748 2.788 0.68% 6/6 > [ 10] image swfdec-giant-steps 2.717 2.736 0.48% 6/6 > [ 11] image swfdec-youtube 4.383 4.414 0.57% 6/6 > [ 12] image xfce4-terminal-a1 4.055 4.076 0.52% 6/6 > > Without prefetching: > > [ # ] backend test min(s) median(s) stddev. count > [ 0] image evolution 17.310 17.351 1.64% 6/6 > [ 1] image firefox-planet-gnome 25.816 27.148 2.33% 6/6 > [ 2] image firefox-talos-gfx 13.176 13.214 0.15% 6/6 > [ 3] image firefox-talos-svg 61.269 61.319 0.08% 5/6 > [ 4] image gnome-system-monitor 7.386 7.415 0.28% 6/6 > [ 5] image gnome-terminal-vim 4.116 4.163 0.45% 6/6 > [ 6] image gvim 22.659 22.901 1.46% 6/6 > [ 7] image midori-zoomed 5.713 5.714 0.03% 5/6 > [ 8] image ocitysmap 3.997 4.000 0.09% 6/6 > [ 9] image poppler 2.796 2.797 0.07% 5/6 > [ 10] image swfdec-giant-steps 2.741 2.754 0.20% 6/6 > [ 11] image swfdec-youtube 4.406 4.415 0.29% 6/6 > [ 12] image xfce4-terminal-a1 4.079 4.089 0.10% 6/6 > > With prefetchnta prefetching: > > [ # ] backend test min(s) median(s) stddev. count > [ 0] image evolution 18.041 18.166 0.29% 4/6 > [ 1] image firefox-planet-gnome 27.042 27.149 0.15% 6/6 > [ 2] image firefox-talos-gfx 13.216 13.255 0.15% 6/6 > [ 3] image firefox-talos-svg 61.118 61.161 0.05% 5/6 > [ 4] image gnome-system-monitor 7.399 7.412 0.14% 5/6 > [ 5] image gnome-terminal-vim 4.170 4.178 0.14% 5/6 > [ 6] image gvim 20.473 22.519 4.43% 7/7 > [ 7] image midori-zoomed 5.567 5.633 0.66% 6/6 > [ 8] image ocitysmap 4.005 4.012 0.16% 4/6 > [ 9] image poppler 2.771 2.795 0.78% 6/6 > [ 10] image swfdec-giant-steps 2.735 2.741 0.23% 6/6 > [ 11] image swfdec-youtube 4.385 4.394 0.42% 6/6 > [ 12] image xfce4-terminal-a1 4.060 4.091 0.31% 5/6 > > > Soren > _______________________________________________ > Pixman mailing list > [email protected] > http://lists.freedesktop.org/mailman/listinfo/pixman > _______________________________________________ Pixman mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/pixman
