On Thu, May 5, 2011 at 4:16 PM, aaron morton <aa...@thelastpickle.com> wrote: > Hannes, > To get a baseline of behaviour set disk_access to standard. You will > probably want to keep it like that if you want better control over the memory > on the box.
I'll do a test with standard and report back. > > Also connect to the box with JConsole and look at the PermGen space > used it is not included in the max heap space setting. You can also check the > heap usage there, running inside of 1G is very tricky. PermGen is at 25M which doesn't explain the 700-1000M RSS overhead. Nevertheless, I wasn't aware that PermGen isn't capped by -Xmx, so thank you for pointing it out. > > If you want to keep it inside of 2Gb trying setting the heap max to > 1.5G, use standard IO, disable caches, and use a low memtable threshold (it > depends on how many CF's you have, try 32mb) I'm not sure I follow. Besides the slowly increasing RSS size, Cassandra works great for us with 1G. Don't the caches and memtables live in the heap? I am not seeing any GC pressure at all so 1G should be ok. Or do the caches and memtables have native components attached to them like JNA-allocated memory or direct byte buffers? > > Hope that helps. > > ----------------- > Aaron Morton > Freelance Cassandra Developer > @aaronmorton > http://www.thelastpickle.com > > On 5 May 2011, at 22:30, Hannes Schmidt wrote: > >> This was my first thought, too. We switched to mmap_index_only and >> didn't see any change in behavior. Looking at the smaps file attached >> to my original post, one can see that the mmapped index files take up >> only a minuscule part of RSS. >> >> On Wed, May 4, 2011 at 11:37 PM, Oleg Anastasyev <olega...@gmail.com> wrote: >>> Probably this is because of mmapped io access mode, which is enabled by >>> default >>> in 64-bit VMs - RAM is occupied by data files. >>> If you have such a tight memory reqs, you can turn on standard access mode >>> in >>> storage-conf.xml, but dont expect it to work fast then: >>> <!-- >>> >>> >>> ~ Access mode. mmapped i/o is substantially faster, but only practical on >>> >>> >>> ~ a 64bit machine (which notably does not include EC2 "small" instances) >>> >>> >>> ~ or relatively small datasets. "auto", the safe choice, will enable >>> >>> >>> ~ mmapping on a 64bit JVM. Other values are "mmap", "mmap_index_only" >>> >>> >>> ~ (which may allow you to get part of the benefits of mmap on a 32bit >>> >>> >>> ~ machine by mmapping only index files) and "standard". >>> >>> >>> ~ (The buffer size settings that follow only apply to standard, >>> >>> >>> ~ non-mmapped i/o.) >>> >>> >>> --> >>> >>> >>> <DiskAccessMode>standard</DiskAccessMode> >>> >>> > >
