On 01/07/2013 09:08 PM, Rik van Riel wrote: > On 01/08/2013 12:03 AM, H. Peter Anvin wrote: >> On 01/07/2013 08:55 PM, Shaohua Li wrote: >>> >>> I searched a little bit, the change (doing TLB flush to clear access >>> bit) is >>> made between 2.6.7 - 2.6.8, I can't find the changelog, but I found a >>> patch: >>> http://www.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.7-rc2/2.6.7-rc2-mm2/broken-out/mm-flush-tlb-when-clearing-young.patch >>> >>> >>> The changelog declaims this is for arm/ppc/ppc64. >>> >> >> Not really. It says that those have stumbled over it already. It is >> true in general that this change will make very frequently used pages >> (which stick in the TLB) candidates for eviction. > > That is only true if the pages were to stay in the TLB for a > very very long time. Probably multiple seconds. > >> x86 would seem to be just as affected, although possibly with a >> different frequency. >> >> Do we have any actual metrics on anything here? > > I suspect that if we do need to force a TLB flush for page > reclaim purposes, it may make sense to do that TLB flush > asynchronously. For example, kswapd could kick off a TLB > flush of every CPU in the system once a second, when the > system is under pageout pressure. > > We would have to do this in a smart way, so the kswapds > from multiple nodes do not duplicate the work. > > If people want that kind of functionality, I would be > happy to cook up an RFC patch. > So it sounds like you're saying that this patch should never have been applied in the first place? -hpa -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>