From: Kairui Song <kasong@xxxxxxxxxxx> Hi, this is updated version of previous series: https://lore.kernel.org/linux-mm/20231222102255.56993-1-ryncsn@xxxxxxxxx/ Currently when MGLRU ages, it moves the pages one by one and updates mm counter page by page, which is correct but the overhead can be optimized by batching these operations. In pervious series I only test with memtier which didn't show a good enough improment. Acutally in-mem fio benifits the most from patch 3: Ramdisk fio test in a 4G memcg on a EPYC 7K62 with: fio -name=mglru --numjobs=16 --directory=/mnt --size=960m \ --buffered=1 --ioengine=io_uring --iodepth=128 \ --iodepth_batch_submit=32 --iodepth_batch_complete=32 \ --rw=randread --random_distribution=zipf:0.5 --norandommap \ --time_based --ramp_time=1m --runtime=5m --group_reporting Before this series: bw ( MiB/s): min= 7644, max= 9293, per=100.00%, avg=8777.77, stdev=16.59, samples=9568 iops : min=1956954, max=2379053, avg=2247108.51, stdev=4247.22, samples=9568 After this series (+7.5%): bw ( MiB/s): min= 8462, max= 9902, per=100.00%, avg=9444.77, stdev=16.43, samples=9568 iops : min=2166433, max=2535135, avg=2417858.23, stdev=4205.15, samples=9568 However it's highly related to the actual timing and use case. Besides, batch moving also has a good effect on LRU ordering. Currently when MGLRU ages, it walks the LRU backward, and the protected pages are moved to the tail of newer gen one by one, which reverses the order of pages in LRU. Moving them in batches can help keep their order, only in a small scope though due to the scan limit of MAX_LRU_BATCH pages. I noticed a higher performance gain if there are a lot of pages getting protected, but hard to reproduce, so instead I tested using a simpler benchmark, memtier, also for a more generic result. The main overhead here is not aging but the result is also looking good: Average result of 18 test runs: Before: 44017.78 Ops/sec After patch 1-3: 44890.50 Ops/sec (+1.8%) Some more test result in commit messages. Kairui Song (3): mm, lru_gen: batch update counters on againg mm, lru_gen: move pages in bulk when aging mm, lru_gen: try to prefetch next page when canning LRU mm/vmscan.c | 140 ++++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 124 insertions(+), 16 deletions(-) -- 2.43.0
