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From Maciej Miklas <>
Subject Cassandra 1.1.5 - SerializingCacheProvider - possible memory leak?
Date Mon, 03 Dec 2012 09:14:11 GMT

I have following Cassandra setup on server with 24GB RAM:


key_cache_save_period: 0
row_cache_save_period: 0
key_cache_size_in_mb: 512
row_cache_size_in_mb: 10240
row_cache_provider: SerializingCacheProvider

I'am getting OutOfMemory errors, and VisulalVM shows that Old Gen takes
nearly whole heap.

Those are the Cassandra log messages:

INFO CLibrary JNA mlockall successful
INFO DatabaseDescriptor DiskAccessMode 'auto' determined to be mmap,
indexAccessMode is mmap
INFO DatabaseDescriptor Global memtable threshold is enabled at 1981 MB
INFO CacheService Initializing key cache with capacity of 512 MBs.
INFO CacheService Scheduling key cache save to each 0 seconds (going to
save all keys).
INFO CacheService Initializing row cache with capacity of 10240 MBs and
provider org.apache.cassandra.cache.SerializingCacheProvider
INFO CacheService Scheduling row cache save to each 0 seconds (going to
save all keys).
INFO GCInspector GC for ConcurrentMarkSweep: 1106 ms for 1 collections,
5445489440 used; max is 6232735744
INFO StatusLogger Cache Type                     Size
Capacity               KeysToSave
INFO StatusLogger KeyCache                     831 782
831 782                     all

INFO StatusLogger RowCache                  196404489
 196404688                  all
INFO StatusLogger ColumnFamily       Memtable ops, data
INFO StatusLogger MyCF1                 192828,66056113
INFO StatusLogger MyCF2                 59913,19535021
INFO StatusLogger MyCF3                 124953,59082091
WARN [ScheduledTasks:1] Heap is 0.8623632454134093 full.
 You may need to reduce memtable and/or cache sizes.  Cassandra will now
flush up to the two largest memtables to free up memory.  Adjust
flush_largest_memtables_at threshold in cassandra.yaml if you don't want
Cassandra to do this automatically

1) I've set row cache size to 10GB. Single row needs in serialized form
between 300-500 bytes, this would allow maximum 20 millions row key
    SerializingCacheProvider reports size of 196 millions, how can I
interpret this number?

2) I am using default settings besides changes described above. Since key
cache is small, and off heap cache is active, what is taking space in Old


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