linux-kernel - Re: [PATCH 1/3] mm/page_alloc: don't break highest order freepage if steal

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Date:	Tue, 12 May 2015 09:54:51 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Mel Gorman <mgorman@...e.de>,
	Johannes Weiner <hannes@...xchg.org>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 1/3] mm/page_alloc: don't break highest order freepage
 if steal

On 05/12/2015 09:51 AM, Vlastimil Babka wrote:
>>    {
>>    	struct page *page;
>> +	bool steal_fallback;
>>
>> -retry_reserve:
>> +retry:
>>    	page = __rmqueue_smallest(zone, order, migratetype);
>>
>>    	if (unlikely(!page) && migratetype != MIGRATE_RESERVE) {
>>    		if (migratetype == MIGRATE_MOVABLE)
>>    			page = __rmqueue_cma_fallback(zone, order);
>>
>> -		if (!page)
>> -			page = __rmqueue_fallback(zone, order, migratetype);
>> +		if (page)
>> +			goto out;
>> +
>> +		steal_fallback = __rmqueue_fallback(zone, order, migratetype);

Oh and the variable can be probably replaced by calling 
__rmqueue_fallback directly in the if() below.

>>
>>    		/*
>>    		 * Use MIGRATE_RESERVE rather than fail an allocation. goto
>>    		 * is used because __rmqueue_smallest is an inline function
>>    		 * and we want just one call site
>>    		 */
>> -		if (!page) {
>> +		if (!steal_fallback)
>>    			migratetype = MIGRATE_RESERVE;
>> -			goto retry_reserve;
>> -		}
>> +
>> +		goto retry;
>>    	}
>>
>> +out:
>>    	trace_mm_page_alloc_zone_locked(page, order, migratetype);
>>    	return page;
>>    }
>>
>
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