max number of threads on a system

max number of threads on a system

[joeja]

What limits the number of threads one can have on a Linux system?

I have a simple program that creates an array of threads and it locks up at the creation of somewhere between 250 and 275 threads.

The program just hangs indefinately unless a Control-C is hit.

How can I increase this number or can I?

Thanks, Joe 

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Re: max number of threads on a system

[David Schwartz]

On Thu, 21 Mar 2002 20:05:39 -0500, joeja@mindspring.com wrote:
>What limits the number of threads one can have on a Linux system?

	Common sense, one would hope.

>I have a simple program that creates an array of threads and it locks up at
>the creation of somewhere between 250 and 275 threads.

	If it locks up, that's a bug. I remember older versions of glibc actually 
had this bug. But it should simply fail to create them.

>The program just hangs indefinately unless a Control-C is hit.
>
>How can I increase this number or can I?

	Why increase the number of threads you can create before you trigger a bug? 
Wouldn't it make more sense to *fix* the bug so that pthread_create returns 
an error like it's supposed to?

	In any event, don't create so many threads. Create threads only to keep CPUs 
busy or to pend I/Os that can't be done asynchronously.

	DS

Re: max number of threads on a system

[Davide Libenzi]

On Thu, 21 Mar 2002, David Schwartz wrote:

>
>
> On Thu, 21 Mar 2002 20:05:39 -0500, joeja@mindspring.com wrote:
> >What limits the number of threads one can have on a Linux system?
>
> 	Common sense, one would hope.
>
> >I have a simple program that creates an array of threads and it locks up at
> >the creation of somewhere between 250 and 275 threads.

$ ulimit -u



- Davide

Re: max number of threads on a system

[Bill Davidsen]

On Thu, 21 Mar 2002, Davide Libenzi wrote:

> On Thu, 21 Mar 2002, David Schwartz wrote:
> 
> >
> >
> > On Thu, 21 Mar 2002 20:05:39 -0500, joeja@mindspring.com wrote:
> > >What limits the number of threads one can have on a Linux system?
> >
> > 	Common sense, one would hope.
> >
> > >I have a simple program that creates an array of threads and it locks up at
> > >the creation of somewhere between 250 and 275 threads.
> 
> $ ulimit -u

/proc/sys/kernel/threads-max is the system limit. And "locks up" is odd
unless the application is really poorly written to handle errors. Should
time out and whine ;-)

-- 
bill davidsen <davidsen@tmr.com>
  CTO, TMR Associates, Inc
Doing interesting things with little computers since 1979.

Re: max number of threads on a system

[James Bourne]

On Fri, 22 Mar 2002, Bill Davidsen wrote:

> On Thu, 21 Mar 2002, Davide Libenzi wrote:
> 
> > On Thu, 21 Mar 2002, David Schwartz wrote:
> > 
> > >
> > >
> > > On Thu, 21 Mar 2002 20:05:39 -0500, joeja@mindspring.com wrote:
> > > >What limits the number of threads one can have on a Linux system?
> > >
> > > 	Common sense, one would hope.
> > >
> > > >I have a simple program that creates an array of threads and it locks up at
> > > >the creation of somewhere between 250 and 275 threads.
> > 
> > $ ulimit -u
> 
> /proc/sys/kernel/threads-max is the system limit. And "locks up" is odd
> unless the application is really poorly written to handle errors. Should
> time out and whine ;-)

One thing to note here, using pthreads there is a limit of 1024
threads per process.  There are patches to glibc to increase this
to a larger number (4096 or 8192).

Regards
James Bourne

-- 
James Bourne, Supervisor Data Centre Operations
Mount Royal College, Calgary, AB, CA
www.mtroyal.ab.ca

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Re: max number of threads on a system

[Bill Davidsen]

On Fri, 22 Mar 2002, James Bourne wrote:

> One thing to note here, using pthreads there is a limit of 1024
> threads per process.  There are patches to glibc to increase this
> to a larger number (4096 or 8192).

  Haven't checked to see the limit in NGPT, but I haven't hit it ;-)

-- 
bill davidsen <davidsen@tmr.com>
  CTO, TMR Associates, Inc
Doing interesting things with little computers since 1979.

Re: max number of threads on a system

[Peter Wächtler]

Bill Davidsen wrote:

> On Fri, 22 Mar 2002, James Bourne wrote:
> 
> 
>>One thing to note here, using pthreads there is a limit of 1024
>>threads per process.  There are patches to glibc to increase this
>>to a larger number (4096 or 8192).
>>
> 
>   Haven't checked to see the limit in NGPT, but I haven't hit it ;-)
> 

There is another limit creeping in: pthread mmap()s 2 MB
of stack for each thread. So you run out of address space
on 32 bit systems with threads > 1024 (and smaller)

Re: max number of threads on a system

[Davide Libenzi]

On Fri, 22 Mar 2002, Bill Davidsen wrote:

> On Thu, 21 Mar 2002, Davide Libenzi wrote:
>
> > On Thu, 21 Mar 2002, David Schwartz wrote:
> >
> > >
> > >
> > > On Thu, 21 Mar 2002 20:05:39 -0500, joeja@mindspring.com wrote:
> > > >What limits the number of threads one can have on a Linux system?
> > >
> > > 	Common sense, one would hope.
> > >
> > > >I have a simple program that creates an array of threads and it locks up at
> > > >the creation of somewhere between 250 and 275 threads.
> >
> > $ ulimit -u
>
> /proc/sys/kernel/threads-max is the system limit. And "locks up" is odd
> unless the application is really poorly written to handle errors. Should
> time out and whine ;-)

Around 250 was the old limit for max user processes ( non root ), if i
remember well.



- Davide