Hi All, > Performance testing (Kernel compilation, allmodconfig): > ======================================================= > > The experiments with kernel compilation test, 32 threads, in tmpfs use the > "allmodconfig" that takes ~12 minutes, and has considerable swapout/swapin > activity. The cgroup's memory.max is set to 2G. > > > 64K folios: Kernel compilation/allmodconfig: > ============================================ > > ------------------------------------------------------------------------------- > mm-unstable v7 mm-unstable v7 > ------------------------------------------------------------------------------- > zswap compressor deflate-iaa deflate-iaa zstd zstd > ------------------------------------------------------------------------------- > real_sec 775.83 765.90 769.39 772.63 > user_sec 15,659.10 15,659.14 15,666.28 15,665.98 > sys_sec 4,209.69 4,040.44 5,277.86 5,358.61 > ------------------------------------------------------------------------------- > Max_Res_Set_Size_KB 1,871,116 1,874,128 1,873,200 1,873,488 > ------------------------------------------------------------------------------- > memcg_high 0 0 0 0 > memcg_swap_fail 0 0 0 0 > zswpout 107,305,181 106,985,511 86,621,912 89,355,274 > zswpin 32,418,991 32,184,517 25,337,514 26,522,042 > pswpout 272 80 94 16 > pswpin 274 69 54 16 > thp_swpout 0 0 0 0 > thp_swpout_fallback 0 0 0 0 > 64kB_swpout_fallback 494 0 0 0 > pgmajfault 34,577,545 34,333,290 26,892,991 28,132,682 > ZSWPOUT-64kB 3,498,796 3,460,751 2,737,544 2,823,211 > SWPOUT-64kB 17 4 4 1 > ------------------------------------------------------------------------------- > > [...] > > Summary: > ======== > The performance testing data with usemem 30 processes and kernel > compilation test show 61%-73% throughput gains and 27%-37% sys time > reduction (usemem30) and 4% sys time reduction (kernel compilation) with > zswap_store() large folios using IAA compress batching as compared to > IAA sequential. There is no performance regression for zstd/usemem30 and a > slight 1.5% sys time zstd regression with kernel compilation allmod > config. I think I know why kernel_compilation with zstd shows a regression whereas usemem30 does not. It is because I lock/unlock the acomp_ctx mutex once per folio. This can cause decomp jobs to wait for the mutex, which can cause more compressions, and this repeats. kernel_compilation has 25M+ decomps with zstd, whereas usemem30 has practically no decomps, but is compression-intensive, because of which it benefits the once-per-folio lock acquire/release. I am testing a fix where I return zswap_compress() to do the mutex lock/unlock, and expect to post v8 by end of the day. I would appreciate it if you can hold off on reviewing only the zswap patches [14, 15] in my v7 and instead review the v8 versions of these two patches. Thanks! Kanchana
