88 lines
3.5 KiB
Plaintext
88 lines
3.5 KiB
Plaintext
[[heap-size-settings]]
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[discrete]
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=== Heap size settings
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By default, {es} 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 {es} has enough heap available.
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{es} 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. These two settings must be equal to each 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 line in the logs like the following:
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+
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[source,txt]
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----
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heap size [1.9gb], compressed ordinary object pointers [true]
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----
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* 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 and 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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[source,txt]
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----
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heap address: 0x000000011be00000, size: 27648 MB, zero based Compressed Oops
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----
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+
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This line shows that zero-based compressed oops are enabled. If zero-based
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compressed oops are not enabled, you'll see a line like the following instead:
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+
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[source,txt]
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----
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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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Using `jvm.options.d` is the preferred method for configuring the heap size for
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production deployments.
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It is also possible to set the heap size via the `ES_JAVA_OPTS` environment
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variable. This is generally discouraged for production deployments but is useful
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for testing because it overrides all other means of setting JVM options.
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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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