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From Michael Shuler <mich...@pbandjelly.org>
Subject Re: Memory usage more than heap memory
Date Sat, 11 Apr 2020 18:02:26 GMT
Nodetool isn't really meant for monitoring usage.

There are a number of existing tools to grab and track jvm heap usage. 
Enable JMX and pull the info into something custom, or using a grafana 
template, for instance, which usually uses JMX internally.

ie. this one graphs heap usage historically: 
https://grafana.com/grafana/dashboards/5408

Kind regars,
Michael

On 4/11/20 12:47 PM, HImanshu Sharma wrote:
> Hi
> 
> I am not worried about page cache. I want to monitor memory pressure, I 
> want to check that if heap+non heap usage goes above certain level then 
> I can take certain action. But due to this page cache thing, I am not 
> sure how to find actual memory usage( heap and off heap). Heap will not 
> be more than 8G. Off heap increases with data on disk due to off heap 
> storage of bloom filters and index files. I want to know the exact 
> amount of memory occupied by off heap components. Nodetool info output 
> does not look appropriate to me or I am missing something.
> 
> Regards
> Himanshu
> 
> On Sat, Apr 11, 2020 at 10:13 PM Laxmikant Upadhyay 
> <laxmikant.hcl@gmail.com <mailto:laxmikant.hcl@gmail.com>> wrote:
> 
>     Hi,
> 
>     You can read section 'OS Page Cache Usage' on
>     http://cassandra.apache.org/doc/latest/troubleshooting/use_tools.html
>     Also, don't worry about memory usage (page cache) not decreasing
>     even if no traffic ...it will come down when required (for example:
>     a new application needs it when boot up).
> 
>     On Sat, Apr 11, 2020 at 5:29 PM HImanshu Sharma
>     <himanshusharma0038@gmail.com <mailto:himanshusharma0038@gmail.com>>
>     wrote:
> 
>         Hi
> 
>         I am observing memory usage in top command, but there in RSS it
>         is showing 18G ( which I think is sum of used memo + page
>         cache). I want to know how to find how much used by Cassandra
>         process and how much of it is in page cache. I want this
>         information because I want to check memory usage for monitoring.
> 
>         On Sat, Apr 11, 2020 at 9:42 PM Nitan Kainth
>         <nitankainth@gmail.com <mailto:nitankainth@gmail.com>> wrote:
> 
>             You can look at top command. There is column of memory
> 
> 
>             Regards,
> 
>             Nitan____
> 
>             Cell: 510 449 9629 <tel:510%20449%209629>
> 
> 
>>             On Apr 11, 2020, at 11:10 AM, HImanshu Sharma
>>             <himanshusharma0038@gmail.com
>>             <mailto:himanshusharma0038@gmail.com>> wrote:
>>
>>             
>>             Hi
>>
>>             But I see memory not decreasing even if there is no
>>             traffic on cluster. How can I find actual memory usage by
>>             Cassandra process. If it is  OS page cache then how  to
>>             find how much is page  cache and how much is used by process?
>>
>>             Thanks
>>             Himanshu
>>
>>             On Sat, Apr 11, 2020 at 9:07 PM Laxmikant Upadhyay
>>             <laxmikant.hcl@gmail.com <mailto:laxmikant.hcl@gmail.com>>
>>             wrote:
>>
>>                 It is OS page cache used during read..your os will
>>                 leverage memory if not being used by any other
>>                 applications and it improves your read performance.
>>
>>                 On Sat, Apr 11, 2020, 12:47 PM HImanshu Sharma
>>                 <himanshusharma0038@gmail.com
>>                 <mailto:himanshusharma0038@gmail.com>> wrote:
>>
>>                     Hi
>>
>>                     I am very new to the use of cassandra. In a
>>                     cassandra cluster of 3 nodes, I am observing
>>                     memory usage of cassandra process going more than
>>                     the heap memor allocated. As I understand,
>>                     cassandra allocates off heap memory for bloom
>>                     filters, index summary etc.
>>
>>                     When I run nodetool info, I see off heap memory
>>                     usage around 1.5G, my heap is 8G. So memory usage
>>                     should not go above  10G. But in running node it
>>                     goes as high as 18G with heavy loads. It comes
>>                     down with different loads but always more than 12G.
>>
>>                     I would like to know why memory usage is high and
>>                     is there way to control it.
>>
>>                     Thanks
>>                     Himanshu Sharma
>>
> 
> 
>     -- 
> 
>     regards,
>     Laxmikant Upadhyay
> 

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