On 1/18/19 6:51 PM, Mel Gorman wrote: > Once fast searching finishes, there is a possibility that the linear > scanner is scanning full blocks found by the fast scanner earlier. This > patch uses an adaptive stride to sample pageblocks for free pages. The > more consecutive full pageblocks encountered, the larger the stride until > a pageblock with free pages is found. The scanners might meet slightly > sooner but it is an acceptable risk given that the search of the free > lists may still encounter the pages and adjust the cached PFN of the free > scanner accordingly. > > 5.0.0-rc1 5.0.0-rc1 > roundrobin-v3r17 samplefree-v3r17 > Amean fault-both-1 0.00 ( 0.00%) 0.00 * 0.00%* > Amean fault-both-3 2752.37 ( 0.00%) 2729.95 ( 0.81%) > Amean fault-both-5 4341.69 ( 0.00%) 4397.80 ( -1.29%) > Amean fault-both-7 6308.75 ( 0.00%) 6097.61 ( 3.35%) > Amean fault-both-12 10241.81 ( 0.00%) 9407.15 ( 8.15%) > Amean fault-both-18 13736.09 ( 0.00%) 10857.63 * 20.96%* > Amean fault-both-24 16853.95 ( 0.00%) 13323.24 * 20.95%* > Amean fault-both-30 15862.61 ( 0.00%) 17345.44 ( -9.35%) > Amean fault-both-32 18450.85 ( 0.00%) 16892.00 ( 8.45%) > > The latency is mildly improved offseting some overhead from earlier > patches that are prerequisites for the rest of the series. However, > a major impact is on the free scan rate with an 82% reduction. > > 5.0.0-rc1 5.0.0-rc1 > roundrobin-v3r17 samplefree-v3r17 > Compaction migrate scanned 21607271 20116887 > Compaction free scanned 95336406 16668703 > > It's also the first time in the series where the number of pages scanned > by the migration scanner is greater than the free scanner due to the > increased search efficiency. > > Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
