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Re: Serious problems with Java & threads on stable & unstable... (?)

Damian Morris <damian@getsystems.com> writes:

> On a 2.4 kernel, a combination of ulimit and
> /proc/sys/kernel/threads-max is your limit for "regular"
> processes. For threads, additional limitations may be imposed by:
> - the JVM. Prior to 1.3, the Sun JVM's assumed a 2MB stack, imposing
>   a hard limit of 1024 threads.
> - your threads implementation. From the top of my head, prior to
>   around 0.7, LinuxThreads also hard-coded a 2MB stack for threads

This is still true for Debian's x86 libpthread.  In order to get
floating stacks glibc has to be built with --enable-kernel=2.4.0 (or
higher) and for i686.  IIRC Debian's glibc gets built for i386 and

Also glibc, by default, gets built with PTHREAD_THREADS_MAX == 1024.

In any case, it isn't a good idea to use that many threads.  With J2SE
<1.4 it was inevitable in some cases, but J2SE >= 1.4 has non-blocking
multiplexing IO so you don't need a thread for each connection


[1]  There just was a thread about "CPU-optimized" builds on
     debian-devel and all they talked about was performance.  But
     compiling for newer CPUs also can provide non-performance related
     benefits: E.g. compiling glibc for i686 gives you floating
     stacks and high precision timing.

Juergen Kreileder, Blackdown Java-Linux Team
Run Java 2 SE v1.3.1 on your iPAQ:

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