On Thu 22-02-18 18:13:11, Andrey Ryabinin wrote: > > > On 02/22/2018 05:09 PM, Michal Hocko wrote: > > 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 $loop_pid > >> > >> > >> I think the additional loops add some overhead and it's not that big by itself, but > >> this small overhead allows task to refill slightly more pages, increasing > >> the total amount of pages that mem_cgroup_resize_limit() need to reclaim. > >> > >> By using the following commands to show the the amount of reclaimed pages: > >> perf record -e vmscan:mm_vmscan_memcg_reclaim_end echo 50M > /sys/fs/cgroup/memory/test/memory.limit_in_bytes > >> perf script|cut -d '=' -f 2| paste -sd+ |bc > >> > >> I've got 1259841 pages (4.9G) with the patch vs 1394312 pages (5.4G) without it. > > > > So how does the picture changes if you have multiple producers? > > > > Drastically, in favor of the patch. But numbers *very* fickle from run to run. > > Inside 5G vm with 4 cpus (qemu -m 5G -smp 4) and 4 processes in cgroup reading 1G files: > "while true; do cat /1g_f$i > /dev/null; done &" > > with the patch: > best: 1.04 secs, 9.7G reclaimed > worst: 2.2 secs, 16G reclaimed. > > without: > best: 5.4 sec, 35G reclaimed > worst: 22.2 sec, 136G reclaimed Could you also compare how much memory do we reclaim with/without the patch? -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
