On Thu 22-02-18 16:50:33, Andrey Ryabinin wrote: > On 02/21/2018 11:17 PM, Andrew Morton wrote: > > On Fri, 19 Jan 2018 16:11:18 +0100 Michal Hocko <mhocko@xxxxxxxxxx> wrote: > > > >> And to be honest, I do not really see why keeping retrying from > >> mem_cgroup_resize_limit should be so much faster than keep retrying from > >> the direct reclaim path. We are doing SWAP_CLUSTER_MAX batches anyway. > >> mem_cgroup_resize_limit loop adds _some_ overhead but I am not really > >> sure why it should be that large. > > > > Maybe restarting the scan lots of times results in rescanning lots of > > ineligible pages at the start of the list before doing useful work? > > > > Andrey, are you able to determine where all that CPU time is being spent? > > > > I should have been more specific about the test I did. The full script looks like this: > > mkdir -p /sys/fs/cgroup/memory/test > echo $$ > /sys/fs/cgroup/memory/test/tasks > cat 4G_file > /dev/null > while true; do cat 4G_file > /dev/null; done & > loop_pid=$! > perf stat echo 50M > /sys/fs/cgroup/memory/test/memory.limit_in_bytes > echo -1 > /sys/fs/cgroup/memory/test/memory.limit_in_bytes > kill $loop_pid > > > I think the additional loops add some overhead and it's not that big by itself, but > this small overhead allows task to refill slightly more pages, increasing > the total amount of pages that mem_cgroup_resize_limit() need to reclaim. > > By using the following commands to show the the amount of reclaimed pages: > perf record -e vmscan:mm_vmscan_memcg_reclaim_end echo 50M > /sys/fs/cgroup/memory/test/memory.limit_in_bytes > perf script|cut -d '=' -f 2| paste -sd+ |bc > > I've got 1259841 pages (4.9G) with the patch vs 1394312 pages (5.4G) without it. So how does the picture changes if you have multiple producers? -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
