Re: More threads

David Xu <davidxu@xxxxxxxxxxx> · Tue, 06 Dec 2005 18:33:31 +0800

Michael Vince wrote:

Hi All,
I been benchmarking a Java servlet I have created and I want to be able 
to handle a massive amount of simultaneous connections.

So far using benchmarking tools I have been able to get around 2,565 
threads on the Tomcat 5.5 Java process (with native 1.4.2 Java) 
according to ps -auxwH | grep -c 'java'
But I just can't seem to get past that mark, I have a lot of memory 
currently the Tomcat is allocated 2gigs of memory.
When I max it out with my benchmarks I get this in catalina Tomcat 5.5 
but there is still plenty of free memory to the Tomcat process.

SEVERE: Caught exception (java.lang.OutOfMemoryError: unable to create 
new native thread) executing org.apache.jk.common.SocketAcceptor@f36e59, 
terminatingthread
I have been testing with my libmap.conf with these different types of 
implementations.
[/usr/local/jdk1.4.2/]
#libpthread.so           libc_r.so
#libpthread.so.2           libc_r.so.6
libpthread.so.2         libthr.so.2
libpthread.so           libthr.so
libc_r.so.6             libthr.so.2
libc_r.so               libthr.so
I have been getting the best performance with libthr and have been using 
the above libthr and with these settings below.
I have set my max_threads in /etc/sysctl.conf to a massive amount.
kern.threads.max_threads_per_proc=40000
kern.threads.max_groups_per_proc=40000
ps -auxwH | grep -c 'java'
2565
I am using Apache2.2 with the new built in AJP module which has been a 
great addition to Apache 2.2.

I have been able to get the setup performing most stable (no 503 status 
errors) but with less performance / threads with the libmap.conf below.

[/usr/local/jdk1.4.2/]

libpthread.so           libc_r.so

libpthread.so.2           libc_r.so.6
I am on 6.0 Release i386, dual Intel P4, generic SMP kernel.
With Tomcat on Windows XP I have been able to get it running better.

Does any one know of some other sysctls that increase the amount of 
threads in libthr which I am assuming utilizes the above sysctls. Does 
any one know how many threads can be created in Java on FreeBSD?
Cheers,
Mike
Number of threads you can create if you use libthr is limited by
following factors:
1) sysctl:
kern.threads.max_threads_per_proc
kern.threads.max_groups_per_proc
2) stack
per-thread userland stack, default number on 64 bits platform is 2M,
on 32 bits platform, it is 1M. I don't know whether java supports
adjusting default per-thread stack size. if can not, we may add
an environment variable to thread libraries, for example:
LIBPTHREAD_THREAD_STACKSIZE allows user to set default stack size.
Thread also needs a kernel mode stack when it is in kernel, if
I am right, it is 16K bytes per-thread. if you create too many
threads, make sure both side won't exhaust address space, and
because kernel stack can not be swapped out when process is
running, you'd make sure physical memory can not be exhausted.
3) check memory limits
type limits command:
Resource limits (current):
  cputime          infinity secs
  filesize         infinity kB
  datasize           524288 kB
  stacksize           65536 kB
  coredumpsize     infinity kB
  memoryuse        infinity kB
  memorylocked     infinity kB
  maxprocesses         5547
  openfiles           11095
  sbsize           infinity bytes
  vmemoryuse       infinity kB
if address space is not large enough, you have to reconfigure kernel
to allow larger space. Fix me if I am wrong.
David Xu
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