[Deploying Sakai] Memory Tab in Admin Workspace

[Matthew Jones]

Responses inline:

On Thu, Feb 18, 2010 at 9:51 AM, Nawaz Azam <nazam at ccsnh.edu> wrote:
>
> ·         *Available Memory*  (the amount of memory that shows here, is
> that per user or for the whole Sakai instance? Does JAVA_OPTS reflect here?)
>
This is making a call to display Runtime.getRuntime().freeMemory()
(BasicMemoryService->getAvailableMemory). [1] The javadocs say "Returns the
amount of free memory in the Java Virtual Machine." [2]. You may want to
look at this java file for more information as this is there the reports on
this page are generated.

> ·         *Reset All Caches* ( Does this free up memory in general? Would
> anyone’s work might get interrupted if there are active sessions when you
> use this button?)
>

Memory management *should* be done by the JVM automatically. This button in
2.5 and 2.6 does make an explicit call to System.gc() when it is pressed.
This was removed for Kernel 1.1 in 2.7 (KNL-415) [3]. Typically garbage
collection and memory management is not something you or the app should
worry about. So you don't have random garbage collection pausing, you may
want to consider the java opt (-XX:+DisableExplicitGC). [4] This would be
more recommended for 2.6+ and jvm 1.6 where these calls are being removed.
This button's main purpose is to clear out ehcache, and the only side effect
would be slower performance after it is cached as all of the calls would
have to go to the database. I'd say it likely only should be used if you
have a custom tool that isn't doing proper cache invalidation, or if you are
using an external provider (like ldap) that had incorrect values in the
local cache.

·         *Status*
>

Status is a report generated from ehcache. [5] I'm not going to explain the
detail, but you can do some research and attempt to tweak the values if you
like, or add your use MemoryService/Cache in local tools. We haven't done
much adjustment to the global cache(s) at Michigan, and it would take quite
a bit of research over time to see if locally adjusting any of these values
(maxElementsInMemory, timeToLiveSeconds, etc) would help you.

[1]
https://source.sakaiproject.org/svn/kernel/trunk/kernel-impl/src/main/java/org/sakaiproject/memory/impl/BasicMemoryService.java[1]

[2] http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Runtime.html
[3]
http://jira.sakaiproject.org/browse/KNL-415?page=com.atlassian.jira.plugin.ext.subversion:subversion-commits-tabpanel
[4] http://www.theserverside.com/news/thread.tss?thread_id=41258
[5] http://ehcache.org/documentation/index.html

>
>
>
>
> I really appreciate your help with this.
>
>
>
> Thanks,
>
> Nawaz.
>
>
>
> Nawaz Azam
>
> Technical Support Specialist
>
> Manchester Community College
>
> 1066 Front Street, Manchester, NH 03102
>
> Work. (603) 668-6706 ext. 313
>
> Cell.    (603) 396-1356
>
> nazam at ccsnh.edu
>
> Opportunities. For Now ... For Life
>
> www.manchestercommunitycollege.edu
>
>
>
>
>
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