On Mon 30-01-12 10:34:49, Peng Haitao wrote: > > Michal Hocko said the following on 2012-1-4 0:04: > > On Wed 28-12-11 17:23:04, Peng Haitao wrote: > >> > >> memory.memsw.failcnt shows the number of memory+Swap hits limits. > >> So I think when memory+swap usage is equal to limit, memsw.failcnt should be nonzero. > >> > >> I test as follows: > >> > >> # uname -a > >> Linux K-test 3.2.0-rc7-17-g371de6e #2 SMP Wed Dec 28 12:02:52 CST 2011 x86_64 x86_64 x86_64 GNU/Linux > >> # mkdir /cgroup/memory/group > >> # cd /cgroup/memory/group/ > >> # echo 10M > memory.limit_in_bytes > >> # echo 10M > memory.memsw.limit_in_bytes > >> # echo $$ > tasks > >> # dd if=/dev/zero of=/tmp/temp_file count=20 bs=1M > >> Killed > >> # cat memory.memsw.failcnt > >> 0 > >> # grep "failcnt" /var/log/messages | tail -2 > >> Dec 28 17:05:52 K-test kernel: memory: usage 10240kB, limit 10240kB, failcnt 21 > >> Dec 28 17:05:52 K-test kernel: memory+swap: usage 10240kB, limit 10240kB, failcnt 0 > >> > >> memory+swap usage is equal to limit, but memsw.failcnt is zero. > >> > > Please note that memsw.limit_in_bytes is triggered only if we have > > consumed some swap space already (and the feature is primarily intended > > to stop extensive swap usage in fact). > > It goes like this: If we trigger hard limit (memory.limit_in_bytes) then > > we start the direct reclaim (with swap available). If we trigger memsw > > limit then we try to reclaim without swap available. We will OOM if we > > cannot reclaim enough to satisfy the respective limit. > > > > The other part of the answer is, yes there is something wrong going > > on her because we definitely shouldn't OOM. The workload is a single > > threaded and we have a plenty of page cache that could be reclaimed > > easily. On the other hand we end up with: > > # echo $$ > tasks > > /dev/memctl/a# echo 10M > memory.limit_in_bytes > > /dev/memctl/a# echo 10M > memory.memsw.limit_in_bytes > > /dev/memctl/a# dd if=/dev/zero of=/tmp/temp_file count=20 bs=1M > > Killed > > /dev/memctl/a# cat memory.stat > > cache 9265152 > > [...] > > > > So there is almost 10M of page cache that we can simply reclaim. If we > > use 40M limit then we are OK. So this looks like the small limit somehow > > tricks our math in the reclaim path and we think there is nothing to > > reclaim. > > I will look into this. > > Have any conclusion for this? I am sorry, but I didn't get to this. The last two months were really busy and I am leaving for a long vacation next week. It's still on my todo list... > Thanks. -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>