On Thu, Jul 04, 2019 at 01:04:25PM +0200, Michal Hocko wrote: > On Thu 04-07-19 17:47:16, Kuo-Hsin Yang wrote: > > On Wed, Jul 03, 2019 at 04:30:57PM +0200, Michal Hocko wrote: > > > > > > How does the reclaim behave with workloads with file backed data set > > > not fitting into the memory? Aren't we going to to swap a lot - > > > something that the heuristic is protecting from? > > > > > > > In common case, most of the pages in a large file backed data set are > > non-executable. When there are a lot of non-executable file pages, > > usually more file pages are scanned because of the recent_scanned / > > recent_rotated ratio. > > > > I modified the test program to set the accessed sizes of the executable > > and non-executable file pages respectively. The test program runs on 2GB > > RAM VM with kernel 5.2.0-rc7 and this patch, allocates 2000 MB anonymous > > memory, then accesses 100 MB executable file pages and 2100 MB > > non-executable file pages for 10 times. The test also prints the file > > and anonymous page sizes in kB from /proc/meminfo. There are not too > > many swaps in this test case. I got similar test result without this > > patch. > > Could you record swap out stats please? Also what happens if you have > multiple readers? Checked the swap out stats during the test [1], 19006 pages swapped out with this patch, 3418 pages swapped out without this patch. There are more swap out, but I think it's within reasonable range when file backed data set doesn't fit into the memory. $ ./thrash 2000 100 2100 5 1 # ANON_MB FILE_EXEC FILE_NOEXEC ROUNDS PROCESSES Allocate 2000 MB anonymous pages active_anon: 1613644, inactive_anon: 348656, active_file: 892, inactive_file: 1384 (kB) pswpout: 7972443, pgpgin: 478615246 Access 100 MB executable file pages Access 2100 MB regular file pages File access time, round 0: 12.165, (sec) active_anon: 1433788, inactive_anon: 478116, active_file: 17896, inactive_file: 24328 (kB) File access time, round 1: 11.493, (sec) active_anon: 1430576, inactive_anon: 477144, active_file: 25440, inactive_file: 26172 (kB) File access time, round 2: 11.455, (sec) active_anon: 1427436, inactive_anon: 476060, active_file: 21112, inactive_file: 28808 (kB) File access time, round 3: 11.454, (sec) active_anon: 1420444, inactive_anon: 473632, active_file: 23216, inactive_file: 35036 (kB) File access time, round 4: 11.479, (sec) active_anon: 1413964, inactive_anon: 471460, active_file: 31728, inactive_file: 32224 (kB) pswpout: 7991449 (+ 19006), pgpgin: 489924366 (+ 11309120) With 4 processes accessing non-overlapping parts of a large file, 30316 pages swapped out with this patch, 5152 pages swapped out without this patch. The swapout number is small comparing to pgpgin. [1]: https://github.com/vovo/testing/blob/master/mem_thrash.c
