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Date: Thu, 3 Mar 2016 16:47:10 +0900
From: Joonsoo Kim <js1304@...il.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Michal Nazarewicz <mina86@...a86.com>,
Minchan Kim <minchan@...nel.org>,
Mel Gorman <mgorman@...hsingularity.net>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
Steven Rostedt <rostedt@...dmis.org>,
Linux Memory Management List <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>, linux-api@...r.kernel.org,
Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH v4 1/2] mm: introduce page reference manipulation functions
2016-03-03 1:44 GMT+09:00 Vlastimil Babka <vbabka@...e.cz>:
> On 02/26/2016 01:58 AM, js1304@...il.com wrote:
>>
>> From: Joonsoo Kim <iamjoonsoo.kim@....com>
>>
>> Success of CMA allocation largely depends on success of migration
>> and key factor of it is page reference count. Until now, page reference
>> is manipulated by direct calling atomic functions so we cannot follow up
>> who and where manipulate it. Then, it is hard to find actual reason
>> of CMA allocation failure. CMA allocation should be guaranteed to succeed
>> so finding offending place is really important.
>>
>> In this patch, call sites where page reference is manipulated are
>> converted
>> to introduced wrapper function. This is preparation step to add tracepoint
>> to each page reference manipulation function. With this facility, we can
>> easily find reason of CMA allocation failure. There is no functional
>> change
>> in this patch.
>>
>> In addition, this patch also converts reference read sites. It will help
>> a second step that renames page._count to something else and prevents
>> later
>> attempt to direct access to it (Suggested by Andrew).
>>
>> Acked-by: Michal Nazarewicz <mina86@...a86.com>
>> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
>
>
> Even without Patch 2/2 this is a nice improvement.
> Acked-by: Vlastimil Babka <vbabka@...e.cz>
>
> Although somebody might be confused by page_ref_count() vs page_count(). Oh
> well.
Yes... it was pointed by Kirill before but consistency is not the purpose of
this patchset so I skipped it. There are too many sites (roughly 100) so I'm not
sure this code churn is worth doing now. If someone think it is really
important,
I will handle it after rc2.
Thanks.
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