Re: [Linux-ia64] Re: [PATCH] Increase size of user stack

[Matthew Wilcox <willy@debian.org>]

On Mon, May 12, 2003 at 10:38:44AM -0400, Martin Hicks wrote:
> On Mon, May 05, 2003 at 11:25:33AM -0700, David Mosberger wrote:
> >   Martin> The current user stack size limit of 2GB is not big enough
> >   Martin> for large SMP or SSI clusters.  The following patch
> >   Martin> increases this size from 2GB to 512GB.  The new size is
> >   Martin> negotiable, but right now SGI has programs that require over
> >   Martin> 100GB of stack size on a 64 processor machine.  Setting the
> >   Martin> user stack size to 512GB seems like a reasonable thing to do
> >   Martin> for future growth.
> > 
> > Why not make it configurable via setrlimit() and be done with it once
> > and for all?
> 
> (sorry for taking so long to respond about this)
> 
> The user stack size is configurable through setrlimit().  The default 
> size of the user stack is 8MB and the max is ~0UL.  The problem is
> the addreses that are chosen for the stack (which grows down) and the
> register backing store (which grows up) are only 2GB apart.  My patch
> simply makes this space 512GB so that large stack are possible, without
> the stack smashing into the RBS.

Yes, but why not choose the addresses based on the current setting of
current->rlim[RLIMIT_STACK].rlim_max?  We could default that setting to
2GB (ie the same as what people are using now) and then set the RBS and
the user stack min(1TB, current->rlim[RLIMIT_STACK].rlim_max) apart.
Are there any disadvantages to doing this?

-- 
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