73 lines
2.9 KiB
Plaintext
73 lines
2.9 KiB
Plaintext
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[[heap-size]]
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=== Setting the heap size
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By default, Elasticsearch tells the JVM to use a heap with a minimum and maximum
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size of 1 GB. When moving to production, it is important to configure heap size
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to ensure that Elasticsearch has enough heap available.
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Elasticsearch will assign the entire heap specified in
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<<jvm-options,jvm.options>> via the `Xms` (minimum heap size) and `Xmx` (maximum
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heap size) settings.
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The value for these setting depends on the amount of RAM available on your
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server. Good rules of thumb are:
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* Set the minimum heap size (`Xms`) and maximum heap size (`Xmx`) to be equal to
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each other.
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* The more heap available to Elasticsearch, the more memory it can use for
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caching. But note that too much heap can subject you to long garbage
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collection pauses.
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* Set `Xmx` to no more than 50% of your physical RAM, to ensure that there is
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enough physical RAM left for kernel file system caches.
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* Don’t set `Xmx` to above the cutoff that the JVM uses for compressed object
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pointers (compressed oops); the exact cutoff varies but is near 32 GB. You can
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verify that you are under the limit by looking for a line in the logs like the
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following:
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+
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heap size [1.9gb], compressed ordinary object pointers [true]
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* Even better, try to stay below the threshold for zero-based compressed oops;
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the exact cutoff varies but 26 GB is safe on most systems, but can be as large
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as 30 GB on some systems. You can verify that you are under the limit by
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starting Elasticsearch with the JVM options `-XX:+UnlockDiagnosticVMOptions
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-XX:+PrintCompressedOopsMode` and looking for a line like the following:
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+
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--
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heap address: 0x000000011be00000, size: 27648 MB, zero based Compressed Oops
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showing that zero-based compressed oops are enabled instead of
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heap address: 0x0000000118400000, size: 28672 MB, Compressed Oops with base: 0x00000001183ff000
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--
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Here are examples of how to set the heap size via the jvm.options file:
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[source,txt]
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------------------
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-Xms2g <1>
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-Xmx2g <2>
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------------------
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<1> Set the minimum heap size to 2g.
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<2> Set the maximum heap size to 2g.
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It is also possible to set the heap size via an environment variable. This can
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be done by commenting out the `Xms` and `Xmx` settings in the
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<<jvm-options,`jvm.options`>> file and setting these values via `ES_JAVA_OPTS`:
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[source,sh]
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------------------
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ES_JAVA_OPTS="-Xms2g -Xmx2g" ./bin/elasticsearch <1>
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ES_JAVA_OPTS="-Xms4000m -Xmx4000m" ./bin/elasticsearch <2>
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------------------
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<1> Set the minimum and maximum heap size to 2 GB.
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<2> Set the minimum and maximum heap size to 4000 MB.
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NOTE: Configuring the heap for the <<windows-service,Windows service>> is
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different than the above. The values initially populated for the Windows service
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can be configured as above but are different after the service has been
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installed. Consult the <<windows-service,Windows service documentation>> for
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additional details.
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