Re: [RFC] memory unplug v5 [1/6] migration by kernel

[Mel Gorman <mel@csn.ul.ie>]

KAMEZAWA Hiroyuki wrote:
> On Thu, 14 Jun 2007 09:12:37 -0700 (PDT)
> Christoph Lameter <clameter@sgi.com> wrote:
> 
>>> An unmapped swapcache page, which is just added to LRU, may be accessed via migrate_page().
>>> But page->mapping is NULL yet. 
>> Yes then lets add a check for page->mapping == NULL there.
>>
>> if (!page->mapping)
>> 	goto unlock;
>>
>> That will retry the migration on the next pass. Add some concise comment 
>> explaining the situation. This is general bug in page migration.
>>
> Ok, will do. thank you for your advice.
> 

I am currently testing what I believe your patches currently look like.
In combination with the isolate lru page fix patch, things are looking
better than they were. Previously I had seen some very bizarre errors
when migrating due to compaction of memory but I'm not seeing them now.
 I hadn't been reporting because it was difficult to tell if migration
was at fault or what memory compaction was doing.

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