For some simple and helpful explanations of the behavior you are
observing, some ideas on what to look for in monitoring, as well as some
interesting experiments on the "play" page (last link), have a look at
https://www.linuxatemyram.com/ - this is general linux memory behavior
and not unique to this software.
The Cassandra-specific configuration change suggestions may be more harm
than help, without an understanding the basic kernel behavior.
Performance benchmarking of your specific workload will be the best way
to gauge whether configurations help or hurt. One ubiquitous Cassandra
recommendation is that nodes should have no swap enabled. Paging out/in
of memory will cause problems, so just don't.
Kind regards,
Michael
On 4/11/20 11:50 AM, Laxmikant Upadhyay wrote:
One more point, if you are worried about high memory usage then read
about disk_access_mode configuration of Cassandra. By default it will
cause high memory usage. Setting it to mmap_index_only can help.
On Sat, Apr 11, 2020 at 5:43 PM Laxmikant Upadhyay
<laxmikant....@gmail.com <mailto:laxmikant....@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
<himanshusharma0...@gmail.com <mailto:himanshusharma0...@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
<nitankai...@gmail.com <mailto:nitankai...@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
<himanshusharma0...@gmail.com
<mailto:himanshusharma0...@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....@gmail.com <mailto:laxmikant....@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
<himanshusharma0...@gmail.com
<mailto:himanshusharma0...@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
--
regards,
Laxmikant Upadhyay
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