On (04/08/07 00:02), Andi Kleen didst pronounce: > On Thursday 02 August 2007 19:21:18 Mel Gorman wrote: > > The NUMA layer only supports NUMA policies for the highest zone. When > > ZONE_MOVABLE is configured with kernelcore=, the the highest zone becomes > > ZONE_MOVABLE. The result is that policies are only applied to allocations > > like anonymous pages and page cache allocated from ZONE_MOVABLE when the > > zone is used. > > > > This patch applies policies to the two highest zones when the highest zone > > is ZONE_MOVABLE. As ZONE_MOVABLE consists of pages from the highest "real" > > zone, it's always functionally equivalent. > > > > The patch has been tested on a variety of machines both NUMA and non-NUMA > > covering x86, x86_64 and ppc64. No abnormal results were seen in kernbench, > > tbench, dbench or hackbench. It passes regression tests from the numactl > > package with and without kernelcore= once numactl tests are patched to > > wait for vmstat counters to update. > > I must honestly say I really hate the patch. It's a horrible hack and makes > fast paths > slower. When I designed mempolicies I especially tried to avoid things > like that, please don't add them through the backdoor now. >
It only affects hot paths in the NUMA case so non-NUMA users will not care. For NUMA users, I have posted patches that eliminate multiple zonelists altogether which will reduce cache footprint (something like 7K per node on x86_64) and make things like MPOL_BIND behave in a consistent manner. That would cost on CPU but save on cache which would (hopefully) result in a net gain in most cases. I would like to go with this patch for now just for policies but for 2.6.23, we could leave it as "policies only apply to ZONE_MOVABLE when it is used" if you really insisted on it. It's less than ideal though for sure. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab - 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/
