linux-kernel - Re: [RFC PATCHv2 2/2] Change khugepaged to respect MMF_THP

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Message-ID: <20140120201525.GA31416@redhat.com>
Date:	Mon, 20 Jan 2014 21:15:25 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Alex Thorlton <athorlton@....com>
Cc:	"Kirill A. Shutemov" <kirill@...temov.name>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Rik van Riel <riel@...hat.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andy Lutomirski <luto@...capital.net>,
	Al Viro <viro@...iv.linux.org.uk>,
	Kees Cook <keescook@...omium.org>,
	Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [RFC PATCHv2 2/2] Change khugepaged to respect MMF_THP_DISABLE
	flag

On 01/20, Alex Thorlton wrote:
>
> No, definitely not.  Upon review, khugepaged_test_exit is the wrong
> place to do this check.  I think I need to move it up to
> khugepaged_scan_mm_slot for this to work correctly.

Why? unless a MMF_THP_DISABLE task does madvise(MADV_HUGEPAGE)
khugepaged_scan_mm_slot() should never see its ->mm ?

Although I got lost a bit, and probably misunderstood... but it
seems to me that whatever you do this patch should not touch
khugepaged_scan_mm_slot.

Oleg.

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