On Fri, Feb 02, 2024 at 08:57:38PM +0800, Chengming Zhou wrote: > On 2024/2/2 02:12, Johannes Weiner wrote: > > Caching "swapout work" is helpful when the system is thrashing. Then > > recently swapped in pages might get swapped out again very soon. It > > certainly makes sense with conventional swap, because keeping a clean > > copy on the disk saves IO work and doesn't cost any additional memory. > > > > But with zswap, it's different. It saves some compression work on a > > thrashing page. But the act of keeping compressed memory contributes > > to a higher rate of thrashing. And that can cause IO in other places > > like zswap writeback and file memory. > > [...] A/B test kernel building in tmpfs directory, memory.max=2GB. > (zswap writeback enabled and shrinker_enabled, one 50GB swapfile) > > From the below results, exclusive mode has fewer scan and refault. > > zswap-invalidate-entry zswap-invalidate-entry-exclusive > real 63.80 63.01 > user 1063.83 1061.32 > sys 290.31 266.15 > zswap-invalidate-entry zswap-invalidate-entry-exclusive > workingset_refault_anon 2383084.40 1976397.40 > workingset_refault_file 44134.00 45689.40 > workingset_activate_anon 837878.00 728441.20 > workingset_activate_file 4710.00 4085.20 > workingset_restore_anon 732622.60 639428.40 > workingset_restore_file 1007.00 926.80 > workingset_nodereclaim 0.00 0.00 > pgscan 14343003.40 12409570.20 > pgscan_kswapd 0.00 0.00 > pgscan_direct 14343003.40 12409570.20 > pgscan_khugepaged 0.00 0.00 That's perfect. Thanks! Would you mind adding all of the above into the changelog? With that, Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
