linux-kernel - Re: [PATCH -mmotm-2010-01-06-14-34] Fix fault count of task in GUP

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Message-ID: <28c262361001111605y3f887558wf3b8bb2ebff59a92@mail.gmail.com>
Date:	Tue, 12 Jan 2010 09:05:41 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Hugh Dickins <hugh.dickins@...cali.co.uk>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>, linux-mm <linux-mm@...ck.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -mmotm-2010-01-06-14-34] Fix fault count of task in GUP

On Tue, Jan 12, 2010 at 8:29 AM, Hugh Dickins
<hugh.dickins@...cali.co.uk> wrote:
> On Mon, 11 Jan 2010, Minchan Kim wrote:
>>
>> get_user_pages calls handle_mm_fault to pin the arguemented
>> task's page. handle_mm_fault cause major or minor fault and
>> get_user_pages counts it into task which is passed by argument.
>>
>> But the fault happens in current task's context.
>> So we have to count it not argumented task's context but current
>> task's one.
>
> Have to?
>
> current simulates a fault into tsk's address space.
> It is not a fault into current's address space.
>
> I can see that this could be argued either way, or even
> that such a "fault" should not be counted at all; but I do not
> see a reason to change the way we have been counting it for years.
>
> Sorry, but NAK (to this and to the v2) -
> unless you have a stronger argument.

Okay. The I/O to get a page happen current's context.
So I thought we have to count it with current.
But now that I think about it, yes. It's not current's _fault_.
I agree with your opinion.

Thanks for correcting me. Hugh.



-- 
Kind regards,
Minchan Kim
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