disk_access_mode: mmap?? set to disk_access_mode: mmap_index_only in cassandra yaml
2012/6/8 Gurpreet Singh <gurpreet.si...@gmail.com>: > Hi, > I am testing cassandra 1.1 on a 1 node cluster. > 8 core, 16 gb ram, 6 data disks raid0, no swap configured > > cassandra 1.1.1 > heap size: 8 gigs > key cache size in mb: 800 (used only 200mb till now) > memtable_total_space_in_mb : 2048 > > I am running a read workload.. about 30 reads/second. no writes at all. > The system runs fine for roughly 12 hours. > > jconsole shows that my heap size has hardly touched 4 gigs. > top shows - > SHR increasing slowly from 100 mb to 6.6 gigs in these 12 hrs > RES increases slowly from 6 gigs all the way to 15 gigs > buffers are at a healthy 25 mb at some point and that goes down to 2 mb in > these 12 hrs > VIRT stays at 85 gigs > > I understand that SHR goes up because of mmap, RES goes up because it is > showing SHR value as well. > > After around 10-12 hrs, the cpu utilization of the system starts increasing, > and i notice that kswapd0 process starts becoming more active. Gradually, > the system cpu becomes high almost 70%, and the client starts getting > continuous timeouts. The fact that the buffers went down from 20 mb to 2 mb > suggests that kswapd0 is probably swapping out the pagecache. > > Is there a way out of this to avoid the kswapd0 starting to do things even > when there is no swap configured? > This is very easily reproducible for me, and would like a way out of this > situation. Do i need to adjust vm memory management stuff like pagecache, > vfs_cache_pressure.. things like that? > > just some extra information, jna is installed, mlockall is successful. there > is no compaction running. > would appreciate any help on this. > Thanks > Gurpreet > >
