linux-kernel - Re: [PATCH v2 01/13] mm: support madvise(MADV

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Message-ID: <20151104021624.GA2476@swordfish>
Date:	Wed, 4 Nov 2015 11:16:24 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Michael Kerrisk <mtk.manpages@...il.com>,
	linux-api@...r.kernel.org, Hugh Dickins <hughd@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Jason Evans <je@...com>, Daniel Micay <danielmicay@...il.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Shaohua Li <shli@...nel.org>, Michal Hocko <mhocko@...e.cz>,
	yalin.wang2010@...il.com,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [PATCH v2 01/13] mm: support madvise(MADV_FREE)

Hi Minchan,

On (11/04/15 10:25), Minchan Kim wrote:
[..]
>+static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
>+                               unsigned long end, struct mm_walk *walk)
>+
...
> +	if (pmd_trans_unstable(pmd))
> +		return 0;

I think it makes sense to update pmd_trans_unstable() and
pmd_none_or_trans_huge_or_clear_bad() comments in asm-generic/pgtable.h
Because they explicitly mention MADV_DONTNEED only. Just a thought.


> @@ -379,6 +502,14 @@ madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
>  		return madvise_remove(vma, prev, start, end);
>  	case MADV_WILLNEED:
>  		return madvise_willneed(vma, prev, start, end);
> +	case MADV_FREE:
> +		/*
> +		 * XXX: In this implementation, MADV_FREE works like
		  ^^^^
		XXX

> +		 * MADV_DONTNEED on swapless system or full swap.
> +		 */
> +		if (get_nr_swap_pages() > 0)
> +			return madvise_free(vma, prev, start, end);
> +		/* passthrough */

	-ss
--
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