On Die, 2011-05-17 at 11:53 -0400, Owen Taylor wrote: > On Tue, 2011-05-17 at 15:03 +0200, Michel Dänzer wrote: > > From: Michel Dänzer <[email protected]> > > > > This should be just as good on average but is less expensive. > > If we're not hitting the cache, isn't the cost of rand() pretty much > noise? On my system, rand() seems to take about 10ns.
I wrote this patch because rand() showed up in profiles, and it increased x11perf -aa10text numbers. > The nice thing about random replacement is that it reliable sticks to > being about "as good" as the average, while predictable strategies tend > to have cases where they work well, and cases which they work badly. > > That is, if you have cache of size 10, does performance degrade smoothly > when you go from 9 glyphs to 11 glyphs, or do you drop off a cliff? I haven't tested this specifically. > If libc rand() is too slow, then some inlined linear-congruential > generator could shave a few cycles. I'm afraid I'm not really interested in working on that though. -- Earthling Michel Dänzer | http://www.vmware.com Libre software enthusiast | Debian, X and DRI developer _______________________________________________ [email protected]: X.Org development Archives: http://lists.x.org/archives/xorg-devel Info: http://lists.x.org/mailman/listinfo/xorg-devel
