# Trouble understanding mlockall behaviour **URL:** \ **Category:** Elasticsearch\ **Created:** [January 29, 2014, 1:01pm UTC](https://discuss.elastic.co/t/trouble-understanding-mlockall-behaviour/15473 "2014-01-29T13:01:33Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![briche\_arnaud](https://avatars.discourse-cdn.com/v4/letter/b/db5fbb/32.png) [@briche\_arnaud](https://discuss.elastic.co/u/briche_arnaud)\ **Post date:** [January 29, 2014, 1:01pm UTC](https://discuss.elastic.co/t/trouble-understanding-mlockall-behaviour/15473/1 "2014-01-29T13:01:33Z")
Hi, Following the advice on different blog post on production setup for Elasticsearch, I'm using -Xms256m -Xmx256 and set bootstrap.mlockall to True. My guess was that the after restart, my Elasticsearch process would use about 256m of ram, and that it's memory usage would remain quasi-constant during it's lifetime. But after the restart, my Elasticsearch process in using about 556m of ram. So, can someone please explain me the behaviour of mlockall ? THx in advance. -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/1c761cf3-98d6-4010-bd46-50849c48b760%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/1c761cf3-98d6-4010-bd46-50849c48b760%40googlegroups.com). For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). ---
**Author:** ![warkolm](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/warkolm/32/39224_2.png) [@warkolm](https://discuss.elastic.co/u/warkolm)\ **Post date:** [January 29, 2014, 10:44pm UTC](https://discuss.elastic.co/t/trouble-understanding-mlockall-behaviour/15473/2 "2014-01-29T22:44:01Z")
This is what it does - [http://linux.die.net/man/2/mlockall](http://linux.die.net/man/2/mlockall) Basically it prevents the memory being moved to swap. Regards, Mark Walkom Infrastructure Engineer Campaign Monitor email: [markw@campaignmonitor.com](mailto:markw@campaignmonitor.com) web: [www.campaignmonitor.com](http://www.campaignmonitor.com) On 30 January 2014 00:01, briche arnaud [briche.arnaud@gmail.com](mailto:briche.arnaud@gmail.com) wrote: > Hi, > > Following the advice on different blog post on production setup for > Elasticsearch, I'm using -Xms256m -Xmx256 and set bootstrap.mlockall to > True. > My guess was that the after restart, my Elasticsearch process would use > about 256m of ram, and that it's memory usage would remain quasi-constant > during it's lifetime. > But after the restart, my Elasticsearch process in using about 556m of ram. > > So, can someone please explain me the behaviour of mlockall ? > > THx in advance. > > -- > You received this message because you are subscribed to the Google Groups > "elasticsearch" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). > To view this discussion on the web visit > [https://groups.google.com/d/msgid/elasticsearch/1c761cf3-98d6-4010-bd46-50849c48b760%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/1c761cf3-98d6-4010-bd46-50849c48b760%40googlegroups.com) > . > For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/CAEM624Z31jzjtLaZVQ\_GwSqf-x6ivDEH-2ObC\_zPMwrzgd7ckA%40mail.gmail.com](https://groups.google.com/d/msgid/elasticsearch/CAEM624Z31jzjtLaZVQ_GwSqf-x6ivDEH-2ObC_zPMwrzgd7ckA%40mail.gmail.com). For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). ---
**Author:** ![Binh\_Ly](https://avatars.discourse-cdn.com/v4/letter/b/ce7236/32.png) [@Binh\_Ly](https://discuss.elastic.co/u/Binh_Ly)\ **Post date:** [January 29, 2014, 11:27pm UTC](https://discuss.elastic.co/t/trouble-understanding-mlockall-behaviour/15473/3 "2014-01-29T23:27:47Z")
Also mlockall may not be supported depending on your OS. -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/6fa34ed9-305e-4e94-8c3d-8f7683dae71a%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/6fa34ed9-305e-4e94-8c3d-8f7683dae71a%40googlegroups.com). For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). ---
**Author:** ![jprante](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/jprante/32/44941_2.png) [@jprante](https://discuss.elastic.co/u/jprante)\ **Post date:** [January 30, 2014, 12:34am UTC](https://discuss.elastic.co/t/trouble-understanding-mlockall-behaviour/15473/4 "2014-01-30T00:34:56Z")
The JVM uses reserved memory, buffers, and stacks beside the heap, most can not be controlled by user settings. To reduce memory as much as possible for a Java process, do not use mlockall tricks, use 32bit JVM and reduce maximum allowed stack size with -Xss (this will affect performance of course) You will also need many tweaks of Elasticsearch default settings to behave under shrinked memory, for index loading, field caches, etc. Jörg -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/CAKdsXoFkHRUsTt-0s7vV\_%2BCNL%2BdUW-erVS4JF\_OiL%2B4h-X4mXg%40mail.gmail.com](https://groups.google.com/d/msgid/elasticsearch/CAKdsXoFkHRUsTt-0s7vV_%2BCNL%2BdUW-erVS4JF_OiL%2B4h-X4mXg%40mail.gmail.com). For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). ---
**Author:** ![briche\_arnaud](https://avatars.discourse-cdn.com/v4/letter/b/db5fbb/32.png) [@briche\_arnaud](https://discuss.elastic.co/u/briche_arnaud)\ **Post date:** [January 30, 2014, 9:52am UTC](https://discuss.elastic.co/t/trouble-understanding-mlockall-behaviour/15473/5 "2014-01-30T09:52:07Z")
Ok, I now understand mlockall. But I'm not asking this question in the context of a memory contrived node; my production nodes have 32G ram; I used this setting in order to prevent OOM of prodution nodes. I may misunderstood the informations a gathered from the web, but I deduced that with the following config params : bootstrap.mlockall: true index.fielddata.cache: node indices.fielddata.cache.size: 40% I would have better control of the memory usage of ES nodes. I still don't understand though, why a node started with -Xms256m -Xmx256 + mlockall: false only take 80M ram while a node started with -Xms256m -Xmx256 + mlockall: true take 600M. On Thu, Jan 30, 2014 at 1:34 AM, [joergprante@gmail.com](mailto:joergprante@gmail.com) \< [joergprante@gmail.com](mailto:joergprante@gmail.com)\> wrote: > The JVM uses reserved memory, buffers, and stacks beside the heap, most > can not be controlled by user settings. > To reduce memory as much as possible for a Java process, do not use > mlockall tricks, use 32bit JVM and reduce maximum allowed stack size with > -Xss (this will affect performance of course) > > You will also need many tweaks of Elasticsearch default settings to behave > under shrinked memory, for index loading, field caches, etc. > > Jörg > > -- > You received this message because you are subscribed to a topic in the > Google Groups "elasticsearch" group. > To unsubscribe from this topic, visit > [https://groups.google.com/d/topic/elasticsearch/DijPr5PNTYM/unsubscribe](https://groups.google.com/d/topic/elasticsearch/DijPr5PNTYM/unsubscribe). > To unsubscribe from this group and all its topics, send an email to > [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). > To view this discussion on the web visit > [https://groups.google.com/d/msgid/elasticsearch/CAKdsXoFkHRUsTt-0s7vV\_%2BCNL%2BdUW-erVS4JF\_OiL%2B4h-X4mXg%40mail.gmail.com](https://groups.google.com/d/msgid/elasticsearch/CAKdsXoFkHRUsTt-0s7vV_%2BCNL%2BdUW-erVS4JF_OiL%2B4h-X4mXg%40mail.gmail.com) > . > > For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). -- -- Arnaud Briche Développeur web / Préstataire de service informatique -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/CADP2VkAD14qs0\_dV7%2BgtaSOrBR3o0rJBWcc-xsyrHH%3DAHXp8cA%40mail.gmail.com](https://groups.google.com/d/msgid/elasticsearch/CADP2VkAD14qs0_dV7%2BgtaSOrBR3o0rJBWcc-xsyrHH%3DAHXp8cA%40mail.gmail.com). For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). ---
**Author:** ![jprante](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/jprante/32/44941_2.png) [@jprante](https://discuss.elastic.co/u/jprante)\ **Post date:** [January 30, 2014, 10:24am UTC](https://discuss.elastic.co/t/trouble-understanding-mlockall-behaviour/15473/6 "2014-01-30T10:24:09Z")
If you have 32G RAM, just configure ES with ES\_HEAP\_SIZE=16g If you want to mess with JVM options, set them to -Xmx16g -Xms16g (look into bin/elasticsearch.in.sh assuming you are on Linux) To answer your question, you have passed wrong args in Xmx to the JVM and the JVM silently resets the heap to the initial heap size, which you can find out with the command java -XX:+PrintFlagsFinal -version | grep HeapSize Jörg -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/CAKdsXoENgdThwdEiktDXLPyFECcsDLBK7kOkAnj-OqV89kbiDg%40mail.gmail.com](https://groups.google.com/d/msgid/elasticsearch/CAKdsXoENgdThwdEiktDXLPyFECcsDLBK7kOkAnj-OqV89kbiDg%40mail.gmail.com). For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [July 6, 2017, 1:54am UTC](https://discuss.elastic.co/t/trouble-understanding-mlockall-behaviour/15473/7 "2017-07-06T01:54:00Z")