Re: thread stacks and strict vm overcommit accounting

[Jakub Jelinek <jakub@redhat.com>]

On Thu, Mar 15, 2007 at 11:08:40PM +0000, Hugh Dickins wrote:
> > appears to increase Committed_AS by around 200kb.  But we've committed to
> > providing it with 8MB for stack.
> > 
> > How come this is correct?
> 
> We've no more committed to providing each instance with 8MB of stack,
> than we've committed to providing each instance with RLIMIT_AS of
> address space.  The rlimits are limits, not commitments, surely?

RLIMIT_STACK only applies to the initial thread, POSIX threads have just
stack size attribute, not maximum thread stack size attribute.
If you set it explicitly with pthread_attr_setstacksize, then libpthread
will honor whatever thread stack size you want, otherwise it just uses
some default thread stack size.  This happens to be in NPTL derived
from RLIMIT_STACK value, but very well could be something else.

	Jakub