Date: Thu, 11 Nov 2004 15:36:53 +0100 From: Ronald Klop <ronald-freebsd8@klop.yi.org> To: mcgregory@e-card.bg, freebsd-java@freebsd.org Subject: Re: Thread's type Message-ID: <opsha1jrjw8527sy@smtp.local> In-Reply-To: <1100119160.700.13.camel@martin151> References: <1100119160.700.13.camel@martin151>
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On Wed, 10 Nov 2004 20:39:21 +0000, Martin Grigorov <mcgregory@e-card.bg> wrote: > Hi all, > > I want to ask what type are Java threads in FreeBSD - green or native ? > I'm using FreeBSD 5.3 and jdk 1.4.2 from ports, actually > /usr/ports/jdk14. > > I am a little bit confused: a sysctl entry > "kern.threads.max_threads_per_proc" says that one process can run max > 1500 threads. But I wrote test and it crashes with: > 'Exception in thread "main" java.lang.OutOfMemoryError: unable to create > new native thread', after starting ~ 8300 threads in the Virtual > Machine. > So it sais "native" in the exception, but they are much more than 1500. Java uses native threads. About the 'kern.threads.max_threads_per_proc' limit: The default thread support of FreeBSD 5 (libpthread) doesn't map userspace threads and kernel thread 1:1. As long as a thread isn't executing in a part of the kernel it doesn't use kernel resources. Use top -H to see all threads that are known to the kernel. If you put this in /etc/libmap.conf you will use a 1:1 thread library and your program will give (the expected) errors around 1500 threads. libpthread.so.1 libthr.so.1 # Everything that uses 'libpthread' libpthread.so libthr.so # now uses libthr. libc_r.so.5 libthr.so.1 # Everything that uses 'libc_r' libc_r.so libthr.so # now uses 'libthr' Because the N:M thread mapping a program can switch between threads without kernel overhead. Ronald. -- Ronald Klop, Amsterdam, The Netherlands
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