Re: [Exist-open] Memory issue - configuration problem?

[Marian S. <m.s...@gm...>]

Hi,

> Ah, yes. While storing a document, eXist buffers index entries in memory 
> before it writes them to disk. It will use as much memory as available, 
> with a certain base amount of memory reserved for the page caches. The 
> buffered index entries will be flushed whenever the memory limit is 
> reached.

Ok, that explains everything :) Maybe this mechanism should be explained 
anywhere in the docs so that other users know about if they run into the 
same issue.


>> Anyway, it would be fine if one could provide an upper limit
>> via conf.xml.
> 
> The problem here is that the Java VM increases its memory use 
> dynamically until it reaches the value set by -Xmx (max size). If the 
> Java application doesn't request more memory, it will never grow above 
> -Xms (min size). This means that if we flush the buffered indexes too 
> early, eXist may just keep running with the minimum amount of memory 
> defined via -Xms. The result is: much more IO than would be necessary, 
> frequent garbage collection and a considerable drop in performance.
> 
> If we want to set a limit, or rather: a flush-all-buffers-threshold, in 
> conf.xml, we would need to set -Xms = -Xmx. This should be possible, 
> though not always desirable.

You're right, limiting should probably be done via proper JVM 
initialization (as it already works ;)).

Regards,
Marian