linux-kernel - Re: [RFC PATCH v3 1/4] mm/page_alloc: fix incorrect isolation behavior by rechecking migratetype

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Date:	Mon, 08 Sep 2014 10:31:29 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Rik van Riel <riel@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Mel Gorman <mgorman@...e.de>,
	Johannes Weiner <hannes@...xchg.org>,
	Minchan Kim <minchan@...nel.org>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Zhang Yanfei <zhangyanfei@...fujitsu.com>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Tang Chen <tangchen@...fujitsu.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Wen Congyang <wency@...fujitsu.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Michal Nazarewicz <mina86@...a86.com>,
	Laura Abbott <lauraa@...eaurora.org>,
	Heesub Shin <heesub.shin@...sung.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Ritesh Harjani <ritesh.list@...il.com>,
	t.stanislaws@...sung.com, Gioh Kim <gioh.kim@....com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v3 1/4] mm/page_alloc: fix incorrect isolation behavior
 by rechecking migratetype

On 08/26/2014 10:08 AM, Joonsoo Kim wrote:

> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index f86023b..51e0d13 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -740,9 +740,15 @@ static void free_one_page(struct zone *zone,
>   	if (nr_scanned)
>   		__mod_zone_page_state(zone, NR_PAGES_SCANNED, -nr_scanned);
>
> +	if (unlikely(has_isolate_pageblock(zone))) {
> +		migratetype = get_pfnblock_migratetype(page, pfn);
> +		if (is_migrate_isolate(migratetype))
> +			goto skip_counting;
> +	}
> +	__mod_zone_freepage_state(zone, 1 << order, migratetype);
> +
> +skip_counting:

Here, wouldn't a simple 'else __mod_zone_freepage_state...' look better 
than goto + label? (same for the following 2 patches). Or does that 
generate worse code?

>   	__free_one_page(page, pfn, zone, order, migratetype);
> -	if (unlikely(!is_migrate_isolate(migratetype)))
> -		__mod_zone_freepage_state(zone, 1 << order, migratetype);
>   	spin_unlock(&zone->lock);
>   }
>
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index d1473b2..1fa4a4d 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -60,6 +60,7 @@ out:
>   		int migratetype = get_pageblock_migratetype(page);
>
>   		set_pageblock_migratetype(page, MIGRATE_ISOLATE);
> +		zone->nr_isolate_pageblock++;
>   		nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE);
>
>   		__mod_zone_freepage_state(zone, -nr_pages, migratetype);
> @@ -83,6 +84,7 @@ void unset_migratetype_isolate(struct page *page, unsigned migratetype)
>   	nr_pages = move_freepages_block(zone, page, migratetype);
>   	__mod_zone_freepage_state(zone, nr_pages, migratetype);
>   	set_pageblock_migratetype(page, migratetype);
> +	zone->nr_isolate_pageblock--;
>   out:
>   	spin_unlock_irqrestore(&zone->lock, flags);
>   }
>

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