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This commit introduces the ability to override JVM options by adding custom JVM options files to a jvm.options.d directory. This simplifies administration of Elasticsearch by not requiring administrators to keep the root jvm.options file in sync with changes that we make to the root jvm.options file. Instead, they are not expected to modify this file but instead supply their own in jvm.options.d. In Docker installations, this means they can bind mount this directory in. In future versions of Elasticsearch, we can consider removing the root jvm.options file (instead, providing all options there as system JVM options).
78 lines
3.3 KiB
Plaintext
78 lines
3.3 KiB
Plaintext
[[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. You should set these two settings to be equal to each
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other.
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The value for these settings depends on the amount of RAM available on your
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server:
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* Set `Xmx` and `Xms` to no more than 50% of your physical RAM. {es} requires
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memory for purposes other than the JVM heap and it is important to leave
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space for this. For instance, {es} uses off-heap buffers for efficient
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network communication, relies on the operating system's filesystem cache for
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efficient access to files, and the JVM itself requires some memory too. It is
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normal to observe the {es} process using more memory than the limit
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configured with the `Xmx` setting.
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* Set `Xmx` and `Xms` to no more than the threshold that the JVM uses for
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compressed object pointers (compressed oops); the exact threshold varies but
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is near 32 GB. You can verify that you are under the threshold by looking for a
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line in the logs like the following:
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+
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heap size [1.9gb], compressed ordinary object pointers [true]
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* Ideally set `Xmx` and `Xms` to no more than the threshold for zero-based
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compressed oops; the exact threshold varies but 26 GB is safe on most
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systems, but can be as large as 30 GB on some systems. You can verify that
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you are under this threshold by starting {es} with the JVM options
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`-XX:+UnlockDiagnosticVMOptions -XX:+PrintCompressedOopsMode` and looking for
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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. If zero-based compressed
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oops are not enabled then you will see a line like the following instead:
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heap address: 0x0000000118400000, size: 28672 MB, Compressed Oops with base: 0x00000001183ff000
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--
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The more heap available to {es}, the more memory it can use for its internal
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caches, but the less memory it leaves available for the operating system to use
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for the filesystem cache. Also, larger heaps can cause longer garbage
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collection pauses.
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Here is an example of how to set the heap size via a `jvm.options.d/` 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 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
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service 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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