Mina, Thanks for that post. Very interesting :-)
What sort of things are you graphing? Standard *nux stuff (mem/cpu/etc)? Or do you have some hooks in to the C* process (I saw somoething about port 1414 in the .yaml file). Best, -g On Thu, Jul 26, 2012 at 9:27 AM, Mina Naguib <mina.nag...@bloomdigital.com> wrote: > > Hi Thomas > > On a modern 64bit server, I recommend you pay little attention to the virtual > size. It's made up of almost everything within the process's address space, > including on-disk files mmap()ed in for zero-copy access. It's not > unreasonable for a machine with N amount RAM to have a process whose virtual > size is several times the value of N. That in and of itself is not > problematic > > In a default cassandra 1.1.x setup, the bulk of that will be your sstables' > data and index files. On linux you can invoke the "pmap" tool on the > cassandra process's PID to see what's in there. Much of it will be anonymous > memory allocations (the JVM heap itself, off-heap data structures, etc), but > lots of it will be references to files on disk (binaries, libraries, mmap()ed > files, etc). > > What's more important to keep an eye on is the JVM heap - typically > statically allocated to a fixed size at cassandra startup. You can get info > about its used/capacity values via "nodetool -h localhost info". You can > also hook up jconsole and trend it over time. > > The other critical piece is the process's RESident memory size, which > includes the JVM heap but also other off-heap data structures and > miscellanea. Cassandra has recently been making more use of off-heap > structures (for example, row caching via SerializingCacheProvider). This is > done as a matter of efficiency - a serialized off-heap row is much smaller > than a classical object sitting in the JVM heap - so you can do more with > less. > > Unfortunately, in my experience, it's not perfect. They still have a cost, > in terms of on-heap usage, as well as off-heap growth over time. > > Specifically, my experience with cassandra 1.1.0 showed that off-heap row > caches incurred a very high on-heap cost (ironic) - see my post at > http://mail-archives.apache.org/mod_mbox/cassandra-user/201206.mbox/%3c6feb097f-287b-471d-bea2-48862b30f...@bloomdigital.com%3E > - as documented in that email, I managed that with regularly scheduled full > GC runs via System.gc() > > I have, since then, moved away from scheduled System.gc() to scheduled row > cache invalidations. While this had the same effect as System.gc() I > described in my email, it eliminated the 20-30 second pause associated with > it. It did however introduce (or may be I never noticed earlier), slow creep > in memory usage outside of the heap. > > It's typical in my case for example for a process configured with 6G of JVM > heap to start up, stabilize at 6.5 - 7GB RESident usage, then creep up slowly > throughout a week to 10-11GB range. Depending on what else the box is doing, > I've experienced the linux OOM killer killing cassandra as you've described, > or heavy swap usage bringing everything down (we're latency-sensitive), etc.. > > And now for the good news. Since I've upgraded to 1.1.2: > 1. There's no more need for regularly scheduled System.gc() > 2. There's no more need for regularly scheduled row cache invalidation > 3. The HEAP usage within the JVM is stable over time > 4. The RESident size of the process appears also stable over time > > Point #4 above is still pending as I only have 3 day graphs since the > upgrade, but they show promising results compared to the slope of the same > graph before the upgrade to 1.1.2 > > So my advice is give 1.1.2 a shot - just be mindful of > https://issues.apache.org/jira/browse/CASSANDRA-4411 > > > On 2012-07-26, at 2:18 AM, Thomas Spengler wrote: > >> I saw this. >> >> All works fine upto version 1.1.0 >> the 0.8.x takes 5GB of memory of an 8GB machine >> the 1.0.x takes between 6 and 7 GB on a 8GB machine >> and >> the 1.1.0 takes all >> >> and it is a problem >> for me it is no solution to wait of the OOM-Killer from the linux kernel >> and restart the cassandraprocess >> >> when my machine has less then 100MB ram available then I have a problem. >> >> >> >> On 07/25/2012 07:06 PM, Tyler Hobbs wrote: >>> Are you actually seeing any problems from this? High virtual memory usage >>> on its own really doesn't mean anything. See >>> http://wiki.apache.org/cassandra/FAQ#mmap >>> >>> On Wed, Jul 25, 2012 at 1:21 AM, Thomas Spengler < >>> thomas.speng...@toptarif.de> wrote: >>> >>>> No one has any idea? >>>> >>>> we tryed >>>> >>>> update to 1.1.2 >>>> DiskAccessMode standard, indexAccessMode standard >>>> row_cache_size_in_mb: 0 >>>> key_cache_size_in_mb: 0 >>>> >>>> >>>> Our next try will to change >>>> >>>> SerializingCacheProvider to ConcurrentLinkedHashCacheProvider >>>> >>>> any other proposals are welcom >>>> >>>> On 07/04/2012 02:13 PM, Thomas Spengler wrote: >>>>> Hi @all, >>>>> >>>>> since our upgrade form cassandra 1.0.3 to 1.1.0 the virtual memory usage >>>>> of the cassandra-nodes explodes >>>>> >>>>> our setup is: >>>>> * 5 - centos 5.8 nodes >>>>> * each 4 CPU's and 8 GB RAM >>>>> * each node holds about 100 GB on data >>>>> * each jvm's uses 2GB Ram >>>>> * DiskAccessMode is standard, indexAccessMode is standard >>>>> >>>>> The memory usage grows upto the whole memory is used. >>>>> >>>>> Just for information, as we had cassandra 1.0.3, we used >>>>> * DiskAccessMode is standard, indexAccessMode is mmap >>>>> * and the ram-usage was ~4GB >>>>> >>>>> >>>>> can anyone help? >>>>> >>>>> >>>>> With Regards >
