JVM Heap usage didn't decline after clearing field data cache

Elastic Stack Elasticsearch
1

Hi,
I have a total 8GB of JVM Heap, it't usage was near 50%,
While I cleared field data cache（almost 1GB） using Clear Cache API:
$curl -XPOST 'http://localhost:9200/_cache/clear?field_data=true
'
field data cahced size decreased, indeed, but JVM heap usage didn't
declined.
What's the reasons ?

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2

JVM heap objects are reclaimed by garbage collection, not by clear cache
command.

Jörg

On Wed, Mar 19, 2014 at 4:17 AM, Gary Gao garygaowork@gmail.com wrote:

Hi,
I have a total 8GB of JVM Heap, it't usage was near 50%,
While I cleared field data cache（almost 1GB） using Clear Cache API:
$curl -XPOST 'http://localhost:9200/_cache/
clear?field_data=true'
field data cahced size decreased, indeed, but JVM heap usage didn't
declined.
What's the reasons ?

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3

So, What is Clear Cache API for ?

On Wed, Mar 19, 2014 at 9:22 PM, joergprante@gmail.com <
joergprante@gmail.com> wrote:

JVM heap objects are reclaimed by garbage collection, not by clear cache
command.

Jörg

On Wed, Mar 19, 2014 at 4:17 AM, Gary Gao garygaowork@gmail.com wrote:

Hi,
I have a total 8GB of JVM Heap, it't usage was near 50%,
While I cleared field data cache（almost 1GB） using Clear Cache API:
$curl -XPOST 'http://localhost:9200/_cache/
clear?field_data=true'
field data cahced size decreased, indeed, but JVM heap usage didn't
declined.
What's the reasons ?

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4

For example, if you have a resident filter cache configured and there is
heap congestion, clear cache may temporarily help to release objects back
to the JVM. After a while they are GCed.

Usually, in most other cases, cached objects are GCed when memory becomes
low, so there is not much to worry about clearing cache by command.

Jörg

On Fri, Mar 21, 2014 at 8:19 AM, Gary Gao garygaowork@gmail.com wrote:

So, What is Clear Cache API for ?

On Wed, Mar 19, 2014 at 9:22 PM, joergprante@gmail.com <
joergprante@gmail.com> wrote:

JVM heap objects are reclaimed by garbage collection, not by clear cache
command.

Jörg

On Wed, Mar 19, 2014 at 4:17 AM, Gary Gao garygaowork@gmail.com wrote:

Hi,
I have a total 8GB of JVM Heap, it't usage was near 50%,
While I cleared field data cache（almost 1GB） using Clear Cache API:
$curl -XPOST 'http://localhost:9200/_cache/
clear?field_data=true'
field data cahced size decreased, indeed, but JVM heap usage
didn't declined.
What's the reasons ?

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