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From "Ard Schrijvers" <a.schrijv...@hippo.nl>
Subject RE: Store Janitor configuration
Date Tue, 27 Feb 2007 16:08:25 GMT
Hello Diogo,

First of all, here are some things described about the StoreJanitor: http://cocoon.apache.org/2.1/userdocs/concepts/storejanitor.html

I normally prefer to set freememory low, like to 2 Mb. I think, your setting could easily
lead to your described behavior. It has two implications like you have it now:

1) when the jvm is just perfectly happy, it might have some extra memory in use which will
be cleared upon the next garbage collection. If, however, the StoreJanitor thread would come
by before the garbage collection, it might decide to clear cache entries, while the jvm would
have cleared enough memory

2) Now, suppose, you jvm is critical on memory (it cannot free enough anymore (there are very
many reasons why this could occur)). According your settings, if memory useage is larger then
heapsize and free memory is lower then freememory, the StoreJanitor will remove entries from
cache. This is cocoon's used mechanism to clear cache entries when low on memory. IMO, when
you need your store janitor to remove cache entries, you end up having problems. It removes
randomly from your stores entries, it removes cached xsls, etc etc. My experience is, that
my app actually seems to go worse, when the StoreJanitor is trying to save the app. 

So, if in your case, the Store Janitor does remove entries, you might want to reconfigure
your store settings to prevent the store janitor removing cache entries (if your low on memory
results from to many cached entries in the first place...there are other places where the
problem might be, but the Store Janitor will clear your caches anyway, troubling your app
even more). So, can you tell me what your <store> conf is? You might want to reduce
your maxobjects, and set time2idle to have the cache remove entries. There is though much
to know about this (how the caching works, and how to tune it)

Ard


I'm having problems configuring the memory allocation for the Store Janitor.

if we have something like:

<store-janitor logger="core.store.janitor">
   <parameter name="freememory" value="104857600"/>  
   <parameter name="heapsize" value="515396075"/> <!-- ~ 96% of 512 MB -->
<store-janitor logger="core.store.janitor">

And the JVM is:
 -Xms512m -Xmx512m

Does this mean that that the JVM will always have 104857600 available? What does the JVM with
that amount of memory?


I've put cocoon in DEBUG mode and I'm seeing too many messages "Memory is low!" which is causing
elements to be removed from cache. How can improve this? 
1. Decrease the freememory value?
2. Decrease the heapsize value?
3. Should the value of freememory + heapsize be smaller that the JVM value? 

What's the freememory used by anyway? I know that this is for the JVM, but should this be
changed according to the amount of memory that cocoon needs to run? 

Please let me know what you think of

Many Thanks

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