[concurrency-interest] Default values for maximum thread count in JVM web servers

Nathan Reynolds nathan.reynolds at oracle.com
Mon Apr 15 14:33:47 EDT 2013


Weblogic tries to optimize the throughput by adjusting the number of 
threads.  If the DB connection pool is set to 150, then for DB 
connection constrained workloads, we find the number of threads to hover 
above that (say 175).

However, it really depends upon the work load.  Another work load we run 
on Weblogic maxes out the CPU.  The threads don't block very often.  So, 
the number of threads is usually just above the number of logical 
processors.  For example, on a 24 logical processor machine, the number 
of threads might be around 28.

The article talks about deadlocking due to insufficient threads to do 
all of the parallel processing.  As far as I know (which isn't much), 
Weblogic doesn't do parallel processing.  It does concurrent processing 
of different requests but doesn't use multiple threads to process each 
request... except in some minor cases.  So, having a lot of threads to 
overcome deadlocks isn't necessary.

Nathan Reynolds 
<http://psr.us.oracle.com/wiki/index.php/User:Nathan_Reynolds> | 
Architect | 602.333.9091
Oracle PSR Engineering <http://psr.us.oracle.com/> | Server Technology
On 4/15/2013 6:37 AM, Unmesh Joshi wrote:
> Hi,
>
> I was always curious to know about how the default max thread count in 
> Java web servers are decided. For almost all servers (Tomcat, Weblogic 
> etc..) the default value is always between 150 to 200.
> Is there any specific reason for this number.?
>
> Recently I read a blog explaining why the default max thread count was 
> changed from 25 to 250 in .NET 
> http://www.bluebytesoftware.com/blog/PermaLink,guid,ca22a5a8-a3c9-4ee8-9b41-667dbd7d2108.aspx 
>
>
> Is there any similar reason for default count of 150 to 200 in Java 
> web servers?
>
> Thanks,
> Unmesh
>
>
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