Thanks Ruslan. I will try the mmap_index_only. Is there any guideline as to when to leave it to auto and when to use mmap_index_only?
/G On Fri, Jun 8, 2012 at 1:21 AM, ruslan usifov <ruslan.usi...@gmail.com>wrote: > 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 > > > > >
