Re: Available memory and limit on thread creation

From: marcus (marcus_at_welby.com)
Date: 07/07/04 

Date: Tue, 06 Jul 2004 17:34:35 -0700

OK, I did not read all the replies (most of them over my head!), so this
might have been covered . . .

Your idea of using virtual IP's or another mechanism to run multiple
JVM's seems sound for various reasons. You mentioned server farms,
which indicates you will need to do some amount of distributed
processing eventually anyway, so the logic of distributing the load will
not change dramatically from multiple JVM's or multiple machines.

I use apache to handle connect to tomcat through mod_jk, which specifies
an internal port (JkMount /shop/servlet/* ajp12). It is easy enough for
apache to mount to multiple internal ports using their virtual server
based on the domain of the request, so I wouldn't have to mess with IP's
or even ports (mydomain.com:8080).

Since you already have load balancing in the final equasion, it seems to
me the load balancer could be configured to make requests on
loader1.mydomain.com, loader2.mydomain.com, etc, which transparently
point to separate boxes or separate JVM's on a given box, and you can
deal with the fine points of balancing and maxamising server usage (also
over my head *grin*) when the load is actually present.

(My internal editor suggests the load balancer might have to resort to
rewriting to specific ports like loader1.mydomain.com:8081 and you may
have to configure various apps to start and run listening on
corresponding ports, rather than having another app like apache
distributing requests, but that seems trivial.)

-- clh

Joseph Dionne wrote:
> I am using Linux 2.4 with JVM 1.4.2_04. I have noticed a limit to the
> number of threads that can be created. I tried many settings of "-Xmx"
> and "-Xss" and the largest number of threads I can launch is 1015. So,
> I have several questions.
>
> First, does available memory limit number of threads?
> Second, if available memory does limit the number of threads, is there a
> rule of thumb on how to calculate that limit?
> Finally, exactly what affect do "-Xmx" and "-Xss" have to the VM and do
> they affect thread memory at all?
>
> thanks
> Joseph
>

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