linux-kernel - Re: [PATCH 1/5] mm, page_owner: print migratetype of a page, not pageblock

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Message-ID: <563B1005.3070203@suse.cz>
Date:	Thu, 5 Nov 2015 09:15:01 +0100
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Minchan Kim <minchan@...nel.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Mel Gorman <mgorman@...e.de>
Subject: Re: [PATCH 1/5] mm, page_owner: print migratetype of a page, not
 pageblock

On 11/05/2015 09:09 AM, Joonsoo Kim wrote:
> On Wed, Nov 04, 2015 at 04:00:57PM +0100, Vlastimil Babka wrote:
>> The information in /sys/kernel/debug/page_owner includes the migratetype
>> declared during the page allocation via gfp_flags. This is also checked against
>> the pageblock's migratetype, and reported as Fallback allocation if these two
>> differ (although in fact fallback allocation is not the only reason why they
>> can differ).
>> 
>> However, the migratetype actually printed is the one of the pageblock, not of
>> the page itself, so it's the same for all pages in the pageblock. This is
>> apparently a bug, noticed when working on other page_owner improvements. Fixed.
> 
> We can guess page migratetype through gfp_mask output although it isn't
> easy task for now. But, there is no way to know pageblock migratetype.
> I used this to know how memory is fragmented.

Ah, I see. How bout just we print both migratetypes then and remove the
"Fallback" part, which can be trivially deduced from them (and as I noted it's
somewhat misleading anyway)?

> Thanks.
> 
>> 
>> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
>> ---
>>  mm/page_owner.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/mm/page_owner.c b/mm/page_owner.c
>> index 983c3a1..a9f16b8 100644
>> --- a/mm/page_owner.c
>> +++ b/mm/page_owner.c
>> @@ -113,7 +113,7 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
>>  			"PFN %lu Block %lu type %d %s Flags %s%s%s%s%s%s%s%s%s%s%s%s\n",
>>  			pfn,
>>  			pfn >> pageblock_order,
>> -			pageblock_mt,
>> +			page_mt,
>>  			pageblock_mt != page_mt ? "Fallback" : "        ",
>>  			PageLocked(page)	? "K" : " ",
>>  			PageError(page)		? "E" : " ",
>> -- 
>> 2.6.2
>> 
>> --
>> To unsubscribe, send a message with 'unsubscribe linux-mm' in
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> 

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