# Advice on Heap usage **URL:** \ **Category:** Elasticsearch\ **Created:** [February 4, 2020, 9:33am UTC](https://discuss.elastic.co/t/advice-on-heap-usage/217752 "2020-02-04T09:33:55Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![royal\_man](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/royal_man/32/67426_2.png) [@royal\_man](https://discuss.elastic.co/u/royal_man)\ **Post date:** [February 4, 2020, 9:33am UTC](https://discuss.elastic.co/t/advice-on-heap-usage/217752/1 "2020-02-04T09:33:55Z")
Node: 12cpu + 45GB RAM I have 1 shard on 1 node. size of 1 shard: 12GB Heap assigned: 20GB Based on the graph below. I think I should reduce the heap size but it is recommended to keep heap 50% of the RAM. Can someone suggest. ![Screen Shot 2020-02-04 at 18.22.24](https://us1.discourse-cdn.com/elastic/original/3X/7/2/72e811389245fca566e40d0fcc3c0b127dae61d7.png) Also, `elasticsearch_transport_rx_packets_total` keeps on increasing and search speed becomes bad even if the CPU is 60% utilized. What changes should I perform ? ---
**Author:** ![DavidTurner](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/davidturner/32/22453_2.png) [@DavidTurner](https://discuss.elastic.co/u/DavidTurner)\ **Post date:** [February 4, 2020, 9:49am UTC](https://discuss.elastic.co/t/advice-on-heap-usage/217752/2 "2020-02-04T09:49:01Z")
> [@royal\_man](#): > > it is recommended to keep heap 50% of the RAM This is not the case. The [docs](https://www.elastic.co/guide/en/elasticsearch/reference/current/heap-size.html) say (emphasis mine): > Set `Xmx` and `Xms` to **no more than** 50% of your physical RAM. You can set it to less, for sure, and this can sometimes improve performance. ---
**Author:** ![royal\_man](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/royal_man/32/67426_2.png) [@royal\_man](https://discuss.elastic.co/u/royal_man)\ **Post date:** [February 4, 2020, 10:17am UTC](https://discuss.elastic.co/t/advice-on-heap-usage/217752/3 "2020-02-04T10:17:43Z")
> [@royal\_man](#): > > Also, `elasticsearch_transport_rx_packets_total` keeps on increasing and search speed becomes bad even if the CPU is 60% utilized. What changes should I perform ? @DavidTurner Could you also explain this > Also, elasticsearch\_transport\_rx\_packets\_total keeps on increasing and search speed becomes bad even if the CPU is 60% utilized. What could be the cause for this. ? ---
**Author:** ![royal\_man](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/royal_man/32/67426_2.png) [@royal\_man](https://discuss.elastic.co/u/royal_man)\ **Post date:** [February 4, 2020, 10:19am UTC](https://discuss.elastic.co/t/advice-on-heap-usage/217752/4 "2020-02-04T10:19:40Z")
I found this discussion. Thanks. > [@JVM Heap Advice from documentation](https://discuss.elastic.co/t/jvm-heap-advice-from-documentation/169827/4): > > Note that the documentation gives 50% as a recommended upper limit, not a target: Set Xmx to no more than 50% of your physical RAM You can of course set it lower. I think that reducing the heap size also reduces the space available for off-heap data (they share a limit) but you are right that it increases the space available for filesystem cache. Would that improve performance? It depends™ slight_smile It means a full GC would be faster, but maybe more frequent, and means it can cache … ---
**Author:** ![DavidTurner](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/davidturner/32/22453_2.png) [@DavidTurner](https://discuss.elastic.co/u/DavidTurner)\ **Post date:** [February 4, 2020, 10:34am UTC](https://discuss.elastic.co/t/advice-on-heap-usage/217752/5 "2020-02-04T10:34:31Z")
I've no idea what `elasticsearch_transport_rx_packets_total` is, nor how it relates to your original question. Maybe open a new thread in case someone else knows. ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [March 3, 2020, 10:37am UTC](https://discuss.elastic.co/t/advice-on-heap-usage/217752/6 "2020-03-03T10:37:03Z")
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