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

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Date:	Wed, 27 Jun 2007 15:00:00 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Ulrich Drepper <drepper@...il.com>
CC:	Hugh Dickins <hugh@...itas.com>,
	Davide Libenzi <davidel@...ilserver.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [patch 2/3] MAP_NOZERO - implement sys_brk2()

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.

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