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

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Message-ID: <20070330191323.13f39605@the-village.bc.nu>
Date:	Fri, 30 Mar 2007 19:13:23 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	"Aubrey Li" <aubreylee@...il.com>
Cc:	"David Howells" <dhowells@...hat.com>, 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

> Summary is, when I run the app "time test",
> 
> on x86:
> real    0m0.066s
> user    0m0.008s
> sys     0m0.058s
> 
> on Blackfin:
> real    3m 37.69s
> user    0m 0.04s
> sys     3m 37.58s

What would be relevant would be Blackfin with clearing and blackfin
without

> ---------------------------------------------------------------
> So now the question is,
> 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?

Behaviour.

You can implement a /dev/pages that is a copy of /dev/zero in tiny
amounts of code and use that for the specific problem cases.

Alan
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