linux-kernel - Re: [patch 2/3] MAP_NOZERO

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Message-ID: <Pine.LNX.4.64.0706271218280.5219@alien.or.mcafeemobile.com>
Date:	Wed, 27 Jun 2007 12:22:52 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Rik van Riel <riel@...hat.com>
cc:	Ulrich Drepper <drepper@...il.com>,
	Hugh Dickins <hugh@...itas.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [patch 2/3] MAP_NOZERO - implement sys_brk2()

On Wed, 27 Jun 2007, Rik van Riel wrote:

> Ulrich Drepper wrote:
> > On 6/27/07, Hugh Dickins <hugh@...itas.com> wrote:
> > > Not so: if an mmap can be done by extending either adjacent vma (prot
> > > and flags and file and offset all match up), that's what's done and no
> > > separate vma is created.  (And adjacent vmas get merged when mprotect
> > > removes the difference in protection.)
> > 
> > mmap return values are randomized.  If they would be mergable
> > something would be wrong.
> 
> You can easily pass a hint address to mmap(), causing it to
> extend a malloc arena instead of creating a new VMA.

You mean something like the F_DUPFD, where you pass an fd and that serves 
as from-there-up hint?



- Davide


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