linux-kernel - Re: [PATCH] nommu arch dont zero the anonymous mapping by adding UNINITIALIZE flag

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Date:	Fri, 30 Mar 2007 23:46:31 +0800
From:	"Aubrey Li" <aubreylee@...il.com>
To:	"David Howells" <dhowells@...hat.com>
Cc:	"Alan Cox" <alan@...rguk.ukuu.org.uk>, vapier.adi@...il.com,
	jie.zhang@...log.com, bryan.wu@...log.com,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nommu arch dont zero the anonymous mapping by adding UNINITIALIZE flag

On 3/30/07, David Howells <dhowells@...hat.com> wrote:
> Aubrey Li <aubreylee@...il.com> wrote:
>
> > Keep the same behave as MMU but with bad performance, or keep the same
> > performance as MMU but without the same behave, Which one is more
> > important?
>
> The thing to do is to pass a flag to mmap() to suppress the memset (as
> suggested).  This can then be used by the uClibc malloc() implementation and
> does not impact any application that does an anon mmap() expecting the memory
> returned to be zeroed.
>

As Mike mentioned, it implies breakage in POSIX behavior
and is specific to no-mmu only.

What kind of application does an anonymous mmap() expecting the memory
returned to be zeroed?

-Aubrey
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