Re: 2.2.x process limits (NR_TASKS)?

[Mark Zealey <mark@zealos.org>]

On Thu, Oct 18, 2001 at 03:04:53PM -0400, Brian Gerst wrote:

> Gregory Ade wrote:
> > 
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> > We're running into what appears to be a 256-process-per-user limit on one
> > of our webservers, due to the number of processes running as a specific
> > user for our application.  I'd like to increase the process limit, and
> > *THINK* that to do so i need to increase NR_TASKS in
> > /usr/src/linux/include/linux/tasks.h.
> > 
> > Is this correct?  What other things do I need to watch out for when making
> > this modification?
> > 
> > Also, where can this limit be changed in 2.4.x?
> > 
> > Thanks ahead of time.
> > 
> 
> 2.2.x has a hard limit of 512 tasks on the x86 because it uses hardware
> task switching.  2.4.x allows an unlimited number of tasks, and is
> configurable via /proc/sys/kernel/threads-max and ulimit.

eh? why? The GDT can hold up to 2 ** 16 bytes (limit is 16-bit). Each entry is 8
bytes, that means that there are 8192 possible 'slots' in the GDT. Each process
has 2 entries, an LDT and a task struct entry. Why is the limit 512? couldn't it
be about 4000? (Some entries are needed for APM and other things...)

-- 

Mark Zealey (aka JALH on irc.openprojects.net: #zealos and many more)
mark@zealos.org
mark@itsolve.co.uk

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