linux-kernel - Re: [PATCH 14/28] mm, page_alloc: Simplify last cpupid reset

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Message-ID: <571F6D89.1000704@suse.cz>
Date:	Tue, 26 Apr 2016 15:30:49 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Mel Gorman <mgorman@...hsingularity.net>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Jesper Dangaard Brouer <brouer@...hat.com>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 14/28] mm, page_alloc: Simplify last cpupid reset

On 04/15/2016 11:07 AM, Mel Gorman wrote:
> The current reset unnecessarily clears flags and makes pointless calculations.

Ugh, indeed.

> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>

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

> ---
>   include/linux/mm.h | 5 +----
>   1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index ffcff53e3b2b..60656db00abd 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -837,10 +837,7 @@ extern int page_cpupid_xchg_last(struct page *page, int cpupid);
>
>   static inline void page_cpupid_reset_last(struct page *page)
>   {
> -	int cpupid = (1 << LAST_CPUPID_SHIFT) - 1;
> -
> -	page->flags &= ~(LAST_CPUPID_MASK << LAST_CPUPID_PGSHIFT);
> -	page->flags |= (cpupid & LAST_CPUPID_MASK) << LAST_CPUPID_PGSHIFT;
> +	page->flags |= LAST_CPUPID_MASK << LAST_CPUPID_PGSHIFT;
>   }
>   #endif /* LAST_CPUPID_NOT_IN_PAGE_FLAGS */
>   #else /* !CONFIG_NUMA_BALANCING */
>