Thank you Shawn & Reth!

So I have now some questions, again

Remind: I have only Solr running on this server (i.e.: java + tomcat).

BTW: I needed to increase previously the java heap size because I went out of memory. Actually, you only see here 2Gb (8Gb previously) for JVM because I automatically restart tomcat for a better performance every 30 minutes if no DIH running.

Question #1:
From the picture above, we see Physical memory: ~60Gb
  -> is this because of -Xmx40960m AND -XX:MaxPermSize=20480m ?

Question #2:
"The OS caches the actual index files".

Does this mean that OS will try to cache 47.48Gb for this index? (if not, how can I know the size of the cache)
Or are you speaking about page cache?

Question #3:
"documentCache does live in Java heap"
Is there a way to know the real size used/needed by this caching?

Thanks for your help.

Kind regards,

On 13/04/2016 02:47, Shawn Heisey wrote:
On 4/12/2016 3:35 AM, Bastien Latard - MDPI AG wrote:
Thank you both, Bill and Reth!

Here is my current options from my command to launch java:
*/usr/bin/java  -Xms20480m -Xmx40960m -XX:PermSize=10240m
-XX:MaxPermSize=20480m [...]*

So should I do *-Xms20480m -Xmx20480m*?
Why? What would it change?
You do *NOT* need a 10GB permsize.  That's a definite waste of memory --
most of it will never get used.  It's probably best to let Java handle
the permgen.  This generation is entirely eliminated in Java 8.  In Java
7, the permsize usually doesn't need adjusting ... but if it does, Solr
probably wouldn't even start without an adjustment.

Regarding something said in another reply on this thread:  The
documentCache *does* live in the Java heap, not the OS memory.  The OS
caches the actual index files, and documentCache is maintained by Solr
itself, separately from that.

It is highly unlikely that you will ever need a 40GB heap.  You might
not even need a 20GB heap.  As I said earlier:  Based on what I saw in
your screenshots, I think you can run with an 8g heap (-Xms8g -Xmx8g),
but you might need to try 12g instead.


Kind regards,
Bastien Latard
Web engineer
Postfach, CH-4005 Basel, Switzerland
Office: Klybeckstrasse 64, CH-4057 
Tel. +41 61 683 77 35
Fax: +41 61 302 89 18