[jboss-as7-dev] Limiting Server Thread Usage

[Scott Marlow]

In pull request https://github.com/jbossas/jboss-as/pull/2407, Brian and 
I have been discussing whether the (soon to be async) PU service start() 
should run in a thread from a global thread pool or a private pool owned 
by the PU service.  There was also the suggestion that we create a 
temporary thread for every PU service start.

Has there been any discussion of our general thread pooling design since 
this email discussion (on irc perhaps?) that perhaps captures what we 
want to do next (with regard to deployment/runtime thread pools that are 
currently private and share enough attributes that they could be 
combined into a global thread pool).


On 09/14/2011 01:53 PM, Jason T. Greene wrote:
> Moving to a new thread.
>
> The big problem we run into with this is that almost every application
> of a thread pool that we have needs to be highly tailored to its usage
> to get the most optimal performance. So we end up with quite a few
> different pools and it becomes difficult to impose a server wide limit.
>
> There however some potential strategies we could take. Although I am
> unsure as to how the overall effectiveness would be:
>
> 1. Sharing idle threads between pools
> 2. Force everything to go through a special blocking thread factory via
> instrumentation of java.lang.Thread. Any attempt to allocate over the
> max would lead to thread reclamation attempts and finally blocking until
> a timeout is reached.
> 3. Some kind of auto-tuning weighting model. If the max total threads is
> N, force all thread pools to use a percentage of N, potentially based on
> establishing current config value divided by combined total.
>
> One thing I wonder though is if cloud providers are "barking up the
> wrong tree"? It seems a better limitation of an application is raw CPU
> clock time and max memory usage. How they split that time into threads
> doesn't really affect the scalability of the physical server, it's all
> virtual process performance (who cares if someone wastes time context
> switching?).
>
> On 9/14/11 10:39 AM, Scott Stark wrote:
>   >  The other big cross cutting concern is controlling the total number of
>   >  threads in use by the application server. When running under a
>   >  constrained environment that uses something like pam_limits module to
>   >  control how many process(==java threads) a user can have, it is
>   >  difficult to know what the server max thread usage is right now.
>   >
>