On Fri, Mar 18, 2005 at 07:00:06AM -0800, Christoph Lameter wrote: > On Fri, 18 Mar 2005, Denis Vlasenko wrote: > > > NT stores are not about 5% increase. 200%-300%. Provided you are ok with > > the fact that zeroed page ends up evicted from cache. Luckily, this is > > exactly > > what you want with prezeroing. > > These are pretty significant results. Maybe its best to use non-temporal
The differences are actually less. I do not know what Denis benchmarked, but in my tests the difference was never more than ~10%. He got a zero too much? It does not make any sense if you think of it - the memory bus of the CPU cannot be that much faster than the cache. And the drawback of eating the cache misses later is really very significant. > stores in general for clearing pages? I checked and Itanium has always > used non-temporal stores. So there will be no benefit for us from this That is weird. I would actually try to switch to temporal stores, maybe it will improve some benchmarks. > approach (we have 16k and 64k page sizes which may make the situation a > bit different). Try to update the i386 architectures to do the same? Definitely not. You can experiment with using it for the cleaner daemon, but even there I would use some heuristic to make sure you only use it on a page that are at the end of a pretty long queue. e.g. if you can guarantee that the page allocator will go through 500k-1MB before going to the NT page that is cache cold it may be a good idea. But that might be pretty complicated and I am not sure it will be worth it. But for the clear running in the page fault handler context it is definitely a bad idea. -Andi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
