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
