linux-kernel - Re: [PATCH 08/10] mm/page_alloc: use get_onbuddy

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Date:	Tue, 08 Jul 2014 09:23:13 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Gioh Kim <gioh.kim@....com>, 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, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/10] mm/page_alloc: use get_onbuddy_migratetype() to
 get buddy list type

On 07/08/2014 03:01 AM, Gioh Kim wrote:
>
>
> 2014-07-08 오전 12:57, Vlastimil Babka 쓴 글:
>> On 07/04/2014 09:57 AM, Joonsoo Kim wrote:
>>> When isolating free page, what we want to know is which list
>>> the page is linked. If it is linked in isolate migratetype buddy list,
>>> we can skip watermark check and freepage counting. And if it is linked
>>> in CMA migratetype buddy list, we need to fixup freepage counting. For
>>> this purpose, get_onbuddy_migratetype() is more fit and cheap than
>>> get_pageblock_migratetype(). So use it.
>>
>> Hm but you made get_onbuddy_migratetype() work only with CONFIG_MEMORY_ISOLATION. And __isolate_free_page is (despite the name) not at all limited to CONFIG_MEMORY_ISOLATION.
>>
>
> Current __isolate_free_page is called by only split_free_page, and split_free_page by isolate_freepages_block.
> split_free_page is called only for isolated pages now but It can be changed someday.

Yeah, but isolate_freepages_block is also not part of 
CONFIG_MEMORY_ISOLATION. Unfortunately, there are two distinct concepts 
of memory isolation and LRU isolation, that are not distinguished in 
function names.

> I think get_onbuddy_migratetype should work with any situation.
>
> And I think the name of get_onbuddy_migratetype is confused.
> Because of _onbuddy_, it might look like that the pages are buddy pages.
> I think the original name _freepage_ is proper one.
>
>
>>> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
>>> ---
>>>    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 e1c4c3e..d9fb8bb 100644
>>> --- a/mm/page_alloc.c
>>> +++ b/mm/page_alloc.c
>>> @@ -1597,7 +1597,7 @@ static int __isolate_free_page(struct page *page, unsigned int order)
>>>        BUG_ON(!PageBuddy(page));
>>>
>>>        zone = page_zone(page);
>>> -    mt = get_pageblock_migratetype(page);
>>> +    mt = get_onbuddy_migratetype(page);
>>>
>>>        if (!is_migrate_isolate(mt)) {
>>>            /* Obey watermarks as if the page was being allocated */
>>>
>>
>>
>
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