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From "Thakrar, Jayesh" <>
Subject Re: Apache Cassandra - Memory usage on server
Date Thu, 15 Jun 2017 04:13:44 GMT

The rest of the 42 GB of memory on your server is used by the filesystem buffer cache - see
the "cached" column and the -/+ buffers/cache line.

The OS (Linux) uses all free memory for filesystem buffer cache and if applications need memory,
will relinquish it appropriately.

To see the actual memory footprint of Cassandra, run the command "nodetool -h <hostname>

You will see something like what is show below. Your C* memory usage is the sum of heap and
off heap memory.

ID                     : d4eba1d4-95e7-426c-91c6-8ee57bd4d1a7
Gossip active          : true
Thrift active          : false
Native Transport active: true
Load                   : 130.63 MiB
Generation No          : 1495544782
Uptime (seconds)       : 583743
Heap Memory (MB)       : 645.81 / 4016.00
Off Heap Memory (MB)   : 3.21
Data Center            : datacenter1
Rack                   : rack1
Exceptions             : 0
Key Cache              : entries 76, size 6.92 KiB, capacity 100 MiB, 3995 hits, 4079 requests,
0.979 recent hit rate, 14400 save period in seconds
Row Cache              : entries 0, size 0 bytes, capacity 0 bytes, 0 hits, 0 requests, NaN
recent hit rate, 0 save period in seconds
Counter Cache          : entries 0, size 0 bytes, capacity 50 MiB, 0 hits, 0 requests, NaN
recent hit rate, 7200 save period in seconds
Chunk Cache            : entries 4, size 256 KiB, capacity 480 MiB, 549 misses, 4633 requests,
0.882 recent hit rate, NaN microseconds miss latency
Percent Repaired       : 100.0%
Token                  : (invoke with -T/--tokens to see all 256 tokens)

From: "ZAIDI, ASAD A" <>
Date: Wednesday, June 14, 2017 at 6:23 PM
To: "" <>
Subject: Apache Cassandra - Memory usage on server

Hi folks,

I’m using apache Cassandra 2.2.

Instance is configured with max_heap_size set at 16G, memtable_allocation_type is  offheap_objects
– total available memory is 62G on the server.
There is nothing but Cassandra is running on my Linux server.

My Cassandra instance is consuming all available memory on my machine!

$ free -h
             total       used       free     shared    buffers     cached
Mem:           62G        62G       776M       184K        35M        42G
-/+ buffers/cache:        19G        43G
Swap:         4.0G         0B       4.0G

Can you guys  please suggest how I can limit memory usage of my Cassandra instance and why
C* may be using all available memory?
I’ll much appreciate your suggestions.


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