[jboss-as7-dev] Optimal MSC threadpool size?

[Brian Stansberry]

On 12/9/11 3:03 PM, Dimitris Andreadis wrote:
> Brian, I am not sure I understand, especially the reconciliation bit.
>
> You are saying that whoever is producing the task list to feed to the pool is not breaking
> those tasks into pieces that can be parallelized?
>

In 7.0 the operations that build up the in-memory configuration model, 
load extensions, call service constructors and and tell the MSC to 
install the services are all done on a single thread, called the "boot 
thread". MSC uses a thread pool to parallelize wiring together and 
starting the services, but a lot of work is done on that single thread.

This single threaded boot behavior is the way AS 7.0 always worked. For 
7.1 I added logic to execute a lot of that "boot thread" work in 
parallel. But that logic is disabled if you set 
org.jboss.server.bootstrap.maxThreads.

> In any case, we seem to have many threads sitting there idle.
>
> I suppose, I need to look at the code in more detail.
>
> On 09/12/2011 22:02, Brian Stansberry wrote:
>> If you set org.jboss.server.bootstrap.maxThreads you disable the boot
>> time logic that tries to parallelize running all the operations that
>> load extensions and install subsystems subsystem.
>>
>> Why? Because that parallelization spawns quite a number of threads, and
>> the original intent of org.jboss.server.bootstrap.maxThreads was to
>> control thread counts. And there's been no time to reconcile the two.
>>
>> On 12/9/11 11:39 AM, Dimitris Andreadis wrote:
>>> I was experimenting a bit with the MSC threadpool size
>>> (org.jboss.server.bootstrap.maxThreads) vs boot time and I've put the results here:
>>>
>>> http://community.jboss.org/wiki/ModularServiceContainer-OptimalThreadpoolSize
>>>
>>> On my quad-core/dual-threaded machine with 8 reported processors, the default pool size is
>>> 16 (processors x 2). In most cases this looks like an overkill to me, i.e. you can get
>>> pretty much the same or better results with a thread pool of 4, or even 2.
>>>
>>> Another conclusion seems to be that not too much stuff gets parallelized under the hood?
>>> Even with 1 thread the default config boots pretty much in the same time, while some benefit
>>> kicks in as soon as you have some form of I/O in the full and ha configs. But even then,
>>> with a thread pool of 2 you achieve most of this gain.
>>>
>>> Do I miss something? Do you see different results?
>>>
>>> Just try a single threaded boot:
>>> standalone.bat -Dorg.jboss.server.bootstrap.maxThreads=1
>>>
>>> I am using the latest 7.1.0.CR1-SNAPSHOT
>>>
>>> /D
>>> _______________________________________________
>>> jboss-as7-dev mailing list
>>> jboss-as7-dev at lists.jboss.org
>>> https://lists.jboss.org/mailman/listinfo/jboss-as7-dev
>>
>>
>


-- 
Brian Stansberry
Principal Software Engineer
JBoss by Red Hat