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Date:      Fri, 18 Feb 2000 17:24:08 -0500 (EST)
From:      Daniel Eischen <eischen@vigrid.com>
To:        Matthew Dillon <dillon@apollo.backplane.com>
Cc:        alc@cs.rice.edu, current@FreeBSD.ORG
Subject:   Re: tentitive complete patch for MAP_GUARDED available
Message-ID:  <Pine.SUN.3.91.1000218172009.23954A-100000@pcnet1.pcnet.com>
In-Reply-To: <200002182209.OAA81369@apollo.backplane.com>

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On Fri, 18 Feb 2000, Matthew Dillon wrote:

> :Currently, the threads library only creates one guard page
> :at the top (or bottom depending on how you look at it) of
> :each threads stack (for stacks of default size).  Thread
> :stacks are allocated in sequential zones, so they are always
> :placed on top of the previous threads stack, and thus already
> :have a guard page below the stack.
> :
> :Correct me if I'm wrong, but using MAP_STACK|MAP_GUARDED
> :would allocate one additional guard page for each threads
> :stack.
> :
> :DanE.
> 
>     Correct.  At the moment MAP_GUARDED is a 'generic' guarding flag
>     and makes no assumptions about the areas being adjoining.  It doesn't
>     cost us anything.

Any problem if we overlay a previously MAP_GUARDED page with another
(to save an extra guard page)?

Dan Eischen
eischen@vigrid.com



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