linux-kernel - Re: [PATCH v3 3/3] Prevent activation of page in madvise

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Message-ID: <alpine.LSU.2.00.1011301025010.7450@tigran.mtv.corp.google.com>
Date:	Tue, 30 Nov 2010 10:34:41 -0800 (PST)
From:	Hugh Dickins <hughd@...gle.com>
To:	Minchan Kim <minchan.kim@...il.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Ben Gamari <bgamari.foss@...il.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Nick Piggin <npiggin@...nel.dk>, Mel Gorman <mel@....ul.ie>,
	Wu Fengguang <fengguang.wu@...el.com>
Subject: Re: [PATCH v3 3/3] Prevent activation of page in madvise_dontneed

On Tue, 30 Nov 2010, Minchan Kim wrote:

> Now zap_pte_range alwayas activates pages which are pte_young &&
> !VM_SequentialReadHint(vma). But in case of calling MADV_DONTNEED,
> it's unnecessary since the page wouldn't use any more.
> 
> Signed-off-by: Minchan Kim <minchan.kim@...il.com>
> Acked-by: Rik van Riel <riel@...hat.com>
> Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Nick Piggin <npiggin@...nel.dk>
> Cc: Mel Gorman <mel@....ul.ie>
> Cc: Wu Fengguang <fengguang.wu@...el.com>
> 
> Changelog since v2:
>  - remove unnecessary description
> Changelog since v1: 
>  - change word from promote to activate
>  - add activate argument to zap_pte_range and family function
> 
> ---
>  include/linux/mm.h |    4 ++--
>  mm/madvise.c       |    4 ++--
>  mm/memory.c        |   38 +++++++++++++++++++++++---------------
>  mm/mmap.c          |    4 ++--
>  4 files changed, 29 insertions(+), 21 deletions(-)

Everyone else seems pretty happy with this, and I've not checked
at all whether it achieves your purpose; but personally I'd much
prefer a smaller patch which adds your "activate" or "ignore_references"
flag to struct zap_details, instead of passing this exceptional arg
down lots of levels.  That's precisely the purpose of zap_details,
to gather together a few things that aren't needed in the common case
(though I admit the NULL details defaulting may be ugly).

Hugh
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