linux-kernel - Re: [PATCH v6] add MAP

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Date:	Wed, 20 Jan 2010 09:24:06 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	kosaki.motohiro@...fujitsu.com, Gleb Natapov <gleb@...hat.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
	akpm@...ux-foundation.org, andrew.c.morrow@...il.com,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>, minchan.kim@...il.com
Subject: Re: [PATCH v6] add MAP_UNLOCKED mmap flag

> Hi Gleb,
> 
> On Tue, Jan 19, 2010 at 10:26 AM, Gleb Natapov <gleb@...hat.com> wrote:
> >> design would still be broken, no? Did you try using (or extending)
> >> posix_madvise(MADV_DONTNEED) for the guest address space? It seems to
> > After mlockall() I can't even allocate guest address space. Or do you mean
> > instead of mlockall()? Then how MADV_DONTNEED will help? It just drops
> > page table for the address range (which is not what I need) and does not
> > have any long time effect.
> 
> Oh right, MADV_DONTNEED is no good.

Off topic:

posix_madvise(MADV_DONTNEED) is nop. glibc's posix_madvise(MADV_DONTNEED)
don't call linux's madvise(MADV_DONTNEED).
It's because madvise(MADV_DONTNEED) is not POSIX compliant. 

The behavior of linux madvise(MADV_DONTNEED) is similar to Solaris (or *BSD) 
madvise(MADV_FREE).




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