Database Reference
In-Depth Information
spector.java (line 116) GC for
ConcurrentMarkSweep: 775679 ms, 745236442 reclaimed
leaving 13692736 used; max is
7432306688
INFO [ScheduledTasks:1] 2013-02-20 16:20:45,800
GCInspector.java (line 122) GC for
ParNew: 11080 ms for 2 collections, 885296848 used;
max is 7432306688
INFO [GC inspection] 2013-02-20 16:26:41,136 GCIn-
spector.java (line 116) GC for
ConcurrentMarkSweep: 135562 ms, 814236544 reclaimed
leaving 20652193 used; max is
7432306688
INFO [ScheduledTasks:1] 2013-02-20 17:29:27,148
GCInspector.java (line 122) GC for
ParNew: 16204 ms for 1 collections, 4259366008
used; max is 7432306688
GC should not take longer than a few hundred milliseconds to run on a nor-
mally functioning cluster. In some edge cases of a normally functioning cluster,
you may see your GC patterns moving up to ten to 15 seconds. GC that frequently
takes more than 15 seconds requires some investigation. The most likely cause
is that some portion of the JVM is being swapped out of memory by the OS. A
common problem is that memory-mapped DiskAccessMode is being used without
JNA (Java Native Access) support. The address space will eventually be exhausted
by the memory map, and the OS will swap out the portion of the memory that isn't
in use. The JVM will eventually try to GC this space to reclaim it (which will take
a while).
When this happens, there are a few solutions that can be implemented. Adding
the JNA libraries to the Cassandra class path is the first possibility. They can't
be shipped with Cassandra because of the GPL licensing on the JNA libraries,
but they are freely available for download. The JNA libraries can be downloaded
from GitHub (
https://github.com/twall/jna
). The other option is to set the DiskAc-
cessMode to
mmap_index_only
. This will ensure that Cassandra memory-
maps only the indexes and will therefore use much less memory address space.
It is generally recommended that you shut off swapping if the machine is run-
ning only Cassandra. This lets the OS out-of-memory (OOM) killer kill the Java
