On Fri 17-03-17 17:37:48, Gerhard Wiesinger wrote: [...] > Why does the kernel prefer to swapin/out and not use > > a.) the free memory?
It will use all the free memory up to min watermark which is set up based on min_free_kbytes. > b.) the buffer/cache? the memory reclaim is strongly biased towards page cache and we try to avoid swapout as much as possible (see get_scan_count). > There is ~100M memory available but kernel swaps all the time ... > > Any ideas? > > Kernel: 4.9.14-200.fc25.x86_64 > > top - 17:33:43 up 28 min, 3 users, load average: 3.58, 1.67, 0.89 > Tasks: 145 total, 4 running, 141 sleeping, 0 stopped, 0 zombie > %Cpu(s): 19.1 us, 56.2 sy, 0.0 ni, 4.3 id, 13.4 wa, 2.0 hi, 0.3 si, 4.7 > st > KiB Mem : 230076 total, 61508 free, 123472 used, 45096 buff/cache > > procs -----------memory---------- ---swap-- -----io---- -system-- > ------cpu----- > r b swpd free buff cache si so bi bo in cs us sy id wa st > 3 5 303916 60372 328 43864 27828 200 41420 236 6984 11138 11 47 6 > 23 14 I am really surprised to see any reclaim at all. 26% of free memory doesn't sound as if we should do a reclaim at all. Do you have an unusual configuration of /proc/sys/vm/min_free_kbytes ? Or is there anything running inside a memory cgroup with a small limit? -- Michal Hocko SUSE Labs
