# Heap usage in versions 6 and 7 **URL:** \ **Category:** Elasticsearch\ **Created:** [December 29, 2022, 2:12am UTC](https://discuss.elastic.co/t/heap-usage-in-versions-6-and-7/322127 "2022-12-29T02:12:34Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![casterQ](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/casterq/32/93257_2.png) [@casterQ](https://discuss.elastic.co/u/casterQ)\ **Post date:** [December 29, 2022, 2:12am UTC](https://discuss.elastic.co/t/heap-usage-in-versions-6-and-7/322127/1 "2022-12-29T02:12:34Z")
After upgrading from 6.7.0 to 7.10.2, the amount of data in each data node has decreased, but the heap utilization rate has increased, leading to frequent circuit\_breaking. The 7 version FST has moved to the off heap memory, so the memory utilization rate should be lower？I don't understand. Is there a bug？ ---
**Author:** ![casterQ](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/casterq/32/93257_2.png) [@casterQ](https://discuss.elastic.co/u/casterQ)\ **Post date:** [December 29, 2022, 2:17am UTC](https://discuss.elastic.co/t/heap-usage-in-versions-6-and-7/322127/2 "2022-12-29T02:17:14Z")
3.3TB data per data node of the 6.7.0 version only 1.5TB data per data node of the 7.10.2 version ![image](https://us1.discourse-cdn.com/elastic/original/3X/7/4/7434be1bd506aedb8aea68057a02d959f0f8d189.png) ![image](https://us1.discourse-cdn.com/elastic/original/3X/6/a/6a4d7eadecfd802f76af0d4d6ad1c8cc3814b4a0.png) The data format and cluster settings are the same, but the heap usage of cluster 7 is higher ---
**Author:** ![DJ\_Zhu](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/dj_zhu/32/99543_2.png) [@DJ\_Zhu](https://discuss.elastic.co/u/DJ_Zhu)\ **Post date:** [December 29, 2022, 2:41am UTC](https://discuss.elastic.co/t/heap-usage-in-versions-6-and-7/322127/3 "2022-12-29T02:41:11Z")
You can dump the heap to check which class lead to high usage of heap. ---
**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\ **Post date:** [December 29, 2022, 6:48am UTC](https://discuss.elastic.co/t/heap-usage-in-versions-6-and-7/322127/5 "2022-12-29T06:48:06Z")
What is the full output of the [cluster stats API](https://www.elastic.co/guide/en/elasticsearch/reference/7.17/cluster-stats.html)? I would agree with DJ\_Zhu and recommend having a look at a heap dump to see what is causing the increase. ---
**Author:** ![lno](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/lno/32/85777_2.png) [@lno](https://discuss.elastic.co/u/lno)\ **Post date:** [January 12, 2023, 1:47pm UTC](https://discuss.elastic.co/t/heap-usage-in-versions-6-and-7/322127/6 "2023-01-12T13:47:48Z")
Hi, we got the same problem. Upgrading from 6.8 to 7.17.8 I can see x3 increase in fixed\_bit\_set\_memory\_in\_bytes usage. I would assume it's connected to heavy nested field usage in our mapping, but such an increase is a bit strange. We can see a decrease in terms memory usage but it's not enough to offset the 3x increase in fixed bitset. ---
**Author:** ![casterQ](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/casterq/32/93257_2.png) [@casterQ](https://discuss.elastic.co/u/casterQ)\ **Post date:** [January 17, 2023, 12:53pm UTC](https://discuss.elastic.co/t/heap-usage-in-versions-6-and-7/322127/7 "2023-01-17T12:53:56Z")
How did you solve it？ ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [February 14, 2023, 12:54pm UTC](https://discuss.elastic.co/t/heap-usage-in-versions-6-and-7/322127/8 "2023-02-14T12:54:26Z")
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