linux-kernel - Re: [PATCH -mm V2] do_migrate_pages() calls migrate_to_node() even if task is already on a correct node

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Date:	Tue, 24 Apr 2012 13:16:16 -0400
From:	Larry Woodman <lwoodman@...hat.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
CC:	linux-mm@...ck.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Christoph Lameter <cl@...ux.com>,
	Motohiro Kosaki <mkosaki@...hat.com>,
	Rik van Riel <riel@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH -mm V2] do_migrate_pages() calls migrate_to_node() even
 if task is already on a correct node

On 04/24/2012 12:19 PM, KOSAKI Motohiro wrote:
>> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
>> index 47296fe..6c189fa 100644
>> --- a/mm/mempolicy.c
>> +++ b/mm/mempolicy.c
>> @@ -1012,6 +1012,16 @@ int do_migrate_pages(struct mm_struct *mm,
>>          int dest = 0;
>>
>>          for_each_node_mask(s, tmp) {
>> +
>> +            /* IFF there is an equal number of source and
>> +             * destination nodes, maintain relative node distance
>> +             * even when source and destination nodes overlap.
>> +             * However, when the node weight is unequal, never move
>> +             * memory out of any destination nodes */
>
> Please use
>
> /*
>  * foo bar
>  */
>
> style comment. and this comment only explain how code work but don't 
> explain why.
> I hope the comment describe HPC usecase require to migrate if src and 
> dest have the
> same weight.
>
> Otherwise looks ok. please feel free to use my ack to your next spin.
>  Acked-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
>
>
>
>> +            if ((nodes_weight(*from_nodes) != 
>> nodes_weight(*to_nodes)) &&
>> +                        (node_isset(s, *to_nodes)))
>> +                continue;
>> +
>
>
> -- 
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How does this look:



View attachment "upstream-do_migrate_pages.patch" of type "text/plain" (930 bytes)