On 07/03/2012 09:57 AM, Rik van Riel wrote:
> On 07/02/2012 01:42 PM, Sasha Levin wrote:
>> On Thu, 2012-06-28 at 14:35 -0700, Andrew Morton wrote:
>>> On Thu, 28 Jun 2012 17:24:25 -0400 Rik van Riel<riel@xxxxxxxxxx> wrote:
>>>>
>>>>>> @@ -463,6 +474,8 @@ static void isolate_freepages(struct zone *zone,
>>>>>> */
>>>>>> if (isolated)
>>>>>> high_pfn = max(high_pfn, pfn);
>>>>>> + if (cc->order> 0)
>>>>>> + zone->compact_cached_free_pfn = high_pfn;
>>>>>
>>>>> Is high_pfn guaranteed to be aligned to pageblock_nr_pages here? I
>>>>> assume so, if lots of code in other places is correct but it's
>>>>> unobvious from reading this function.
>>>>
>>>> Reading the code a few more times, I believe that it is
>>>> indeed aligned to pageblock size.
>>>
>>> I'll slip this into -next for a while.
>>>
>>> ---
>>> a/mm/compaction.c~isolate_freepages-check-that-high_pfn-is-aligned-as-expected
>>>
>>> +++ a/mm/compaction.c
>>> @@ -456,6 +456,7 @@ static void isolate_freepages(struct zon
>>> }
>>> spin_unlock_irqrestore(&zone->lock, flags);
>>>
>>> + WARN_ON_ONCE(high_pfn& (pageblock_nr_pages - 1));
>>> /*
>>> * Record the highest PFN we isolated pages from.
>>> When next
>>> * looking for free pages, the search will restart
>>> here as
>>
>> I've triggered the following with today's -next:
>
> I've been staring at the migrate code for most of the afternoon,
> and am not sure how this is triggered.
>
> At this point, I'm going to focus my attention on addressing
> Minchan's comments on my code, and hoping someone who is more
> familiar with the migrate code knows how high_pfn ends up
> being not pageblock_nr_pages aligned...
>
migrate_pfn does not necessarily start aligned to a pageblock.
/* Setup to move all movable pages to the end of the zone */
cc->migrate_pfn = zone->zone_start_pfn;
In isolate_freepages, high_pfn = low_pfn = cc->migrate_pfn + pageblock_nr_pages /* migrate_pfn doesn't aligned to a pageblock */
--
Kind regards,
Minchan Kim
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