linux-kernel - Re: [PATCH] mm: reset migratetype if the range spans two pageblocks

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 16 Oct 2015 18:12:51 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>, Mel Gorman <mgorman@...e.de>,
	<mhocko@...e.com>, <js1304@...il.com>,
	Johannes Weiner <hannes@...xchg.org>,
	<alexander.h.duyck@...hat.com>, <zhongjiang@...wei.com>
CC:	Linux MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: reset migratetype if the range spans two pageblocks

On 2015/10/16 18:06, Xishi Qiu wrote:

> __rmqueue_fallback() will change the migratetype of pageblock,
> so it is possible that two continuous pageblocks have different
> migratetypes.
> 
> When freeing all pages of the two blocks, they will be merged
> to 4M, and added to the buddy list which the migratetype is the
> first pageblock's.
> 
> If later alloc some pages and split the 4M, the second pageblock
> will be added to the buddy list, and the migratetype is the first
> pageblock's, so it is different from the its pageblock's.
> 
> That means the page in buddy list's migratetype is different from
> the page in pageblock's migratetype. This will make confusion.
> 
> However,if we change the hotpath, it will be performance degradation,
> so any better ideas?
> 

How about using get_pfnblock_migratetype() to get the pageblock's
migratetype first, and compare them?

Thanks,
Xishi Qiu

> Signed-off-by: Xishi Qiu <qiuxishi@...wei.com>
> ---
>  mm/page_alloc.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 48aaf7b..5c91348 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -726,6 +726,9 @@ static inline void __free_one_page(struct page *page,
>  	list_add(&page->lru, &zone->free_area[order].free_list[migratetype]);
>  out:
>  	zone->free_area[order].nr_free++;
> +	/* If the range spans two pageblocks, reset the migratetype. */
> +	if (order > pageblock_order)
> +		change_pageblock_range(page, order, migratetype);
>  }
>  
>  static inline int free_pages_check(struct page *page)



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/