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From Bastien Latard - MDPI AG <>
Subject Re: Cache problem
Date Wed, 13 Apr 2016 06:57:16 GMT
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.
> Thanks,
> Shawn

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

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