linux-kernel - Re: [PATCH 11/19] mm: page_alloc: Lookup pageblock migratetype with IRQs enabled during free

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Date:	Tue, 13 May 2014 15:36:25 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	Johannes Weiner <hannes@...xchg.org>, Jan Kara <jack@...e.cz>,
	Michal Hocko <mhocko@...e.cz>, Hugh Dickins <hughd@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Dave Hansen <dave.hansen@...el.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>,
	Linux-FSDevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH 11/19] mm: page_alloc: Lookup pageblock migratetype with
 IRQs enabled during free

On 05/13/2014 11:45 AM, Mel Gorman wrote:
> get_pageblock_migratetype() is called during free with IRQs disabled. This
> is unnecessary and disables IRQs for longer than necessary.
>
> Signed-off-by: Mel Gorman <mgorman@...e.de>
> Acked-by: Rik van Riel <riel@...hat.com>

With a comment below,

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>   mm/page_alloc.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 3948f0a..fcbf637 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -773,9 +773,9 @@ static void __free_pages_ok(struct page *page, unsigned int order)
>   	if (!free_pages_prepare(page, order))
>   		return;
>
> +	migratetype = get_pfnblock_migratetype(page, pfn);
>   	local_irq_save(flags);
>   	__count_vm_events(PGFREE, 1 << order);
> -	migratetype = get_pfnblock_migratetype(page, pfn);
>   	set_freepage_migratetype(page, migratetype);

The line above could be also outside disabled IRQ, no?

>   	free_one_page(page_zone(page), page, pfn, order, migratetype);
>   	local_irq_restore(flags);
>

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