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From Dan Rollo <danro...@gmail.com>
Subject Re: TaskManager thread limit
Date Mon, 02 Aug 2010 07:40:32 GMT
On 08/01/2010 10:00 PM, Patricia Shanahan wrote:
> Gregg Wonderly wrote:
>> Peter Firmstone wrote:
>>> Patricia Shanahan wrote:
>>>> In addition to a limit related to the number of runnable tasks, a
>>>> TaskManager has a hard limit on the number of threads it will create.
>>>>
>>>> The parameterless constructor has limit 10, and most other uses have
>>>> compile time limits in the range of 10 to 15 threads.
>>>>
>>>> com.sun.jini.reggie.RegisrarImpl has a compile time limit of 50
>>>> threads.
>>>>
>>>> com.sun.jini.mahalo.TxnManagerImpl creates two pools, settlerpool
>>>> and taskpool. The settlerpool has limit 150 threads. The taskpool
>>>> has limit 50 threads.
>>>>
>>>> Even 150 threads could be low in a large server, especially if the
>>>> threads are used to wait for anything, so that each thread does not
>>>> need a hardware thread for a significant fraction of its life.
>>>>
>>>> As noted in the NIO vs. IO discussion that Peter pointed out, the
>>>> key to getting good performance simply is to take advantage of the
>>>> fact that an idle thread is a cheap, simple way to remember the
>>>> state of some activity.
>>>>
>>>> There is one approach that would minimize the number of changes but
>>>> increase flexibility. We could redefine the maximum thread count as
>>>> being the maximum number of threads per X, where X is a measure of
>>>> system size with a minimum of 1, but increasing on large systems.
>>>>
>>>> X could be based on the number of processors, the maximum heap
>>>> memory, or some combination.
>>>
>>> I'm in favour of this suggestion.
>>
>> Auto sizing is good, but we should also consider putting in logging
>> that announces when the limit is reached and waiting will occur. This
>> will help people diagnose the potential system pauses, if not deadlock
>> that will be outwardly visible.
>
> Agreed. I would be interested both in the distribution of times that
> tasks spend waiting for other tasks and in the distribution of times
> that they spend as ready tasks, waiting for a thread.
>
>> On top of that, I'd be strongly in favor the introduction of JMX as an
>> external observation and management capability for these types of values.
>
> I don't know much about JMX, but I strongly agree with external
> observation and management.
>
> Incidentally, do you know why the default load level is 3, not 1?
>
> Patricia

Re: JMX - Not even sure this applies, but I remembered the JMX info 
below, and wanted to post it:

https://jmx-lookup.dev.java.net/public/index.html

Dan

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