On Mon, Jan 22, 2024 at 09:01:54PM +0800, Baolin Wang wrote: > Currently we will use 'cc->nr_freepages >= cc->nr_migratepages' comparison > to ensure that enough freepages are isolated in isolate_freepages(), however > it just decreases the cc->nr_freepages without updating cc->nr_migratepages > in compaction_alloc(), which will waste more CPU cycles and cause too many > freepages to be isolated. > > So we should also update the cc->nr_migratepages when allocating or freeing > the freepages to avoid isolating excess freepages. And I can see fewer free > pages are scanned and isolated when running thpcompact on my Arm64 server: > k6.7 k6.7_patched > Ops Compaction pages isolated 120692036.00 118160797.00 > Ops Compaction migrate scanned 131210329.00 154093268.00 > Ops Compaction free scanned 1090587971.00 1080632536.00 > Ops Compact scan efficiency 12.03 14.26 > > Moreover, I did not see an obvious latency improvements, this is likely because > isolating freepages is not the bottleneck in the thpcompact test case. > k6.7 k6.7_patched > Amean fault-both-1 1089.76 ( 0.00%) 1080.16 * 0.88%* > Amean fault-both-3 1616.48 ( 0.00%) 1636.65 * -1.25%* > Amean fault-both-5 2266.66 ( 0.00%) 2219.20 * 2.09%* > Amean fault-both-7 2909.84 ( 0.00%) 2801.90 * 3.71%* > Amean fault-both-12 4861.26 ( 0.00%) 4733.25 * 2.63%* > Amean fault-both-18 7351.11 ( 0.00%) 6950.51 * 5.45%* > Amean fault-both-24 9059.30 ( 0.00%) 9159.99 * -1.11%* > Amean fault-both-30 10685.68 ( 0.00%) 11399.02 * -6.68%* > > Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> -- Mel Gorman SUSE Labs
