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

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Date:	Wed, 1 Dec 2010 09:49:17 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Hugh Dickins <hughd@...gle.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

Hi Hugh,

On Wed, Dec 1, 2010 at 3:34 AM, Hugh Dickins <hughd@...gle.com> wrote:
> 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).

Before I sent RFC, I tried it and suffered from NULL detail as you said.
But it's valuable to look on it, again.
Since other guys don't opposed this patch's goal, I will have a time
for unifying it into zap_details.

Thanks, Hugh.


> Hugh
>



-- 
Kind regards,
Minchan Kim
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