Re: excessive CPU utilization by isolate_freepages?

[Minchan Kim]

On 06/28/2012 10:06 AM, David Rientjes wrote:

> On Thu, 28 Jun 2012, Minchan Kim wrote:
> 
>>>>>>> https://lkml.org/lkml/2012/6/21/30
>>>>>
>>> Not sure if Jim is using memcg; if not, then this won't be helpful.
>>>
>>
>>
>> It doesn't related to memcg.
>> if compaction_alloc can't find suitable migration target, it returns NULL.
>> Then, migrate_pages should be exit.
>>
> 
> If isolate_freepages() is going to fail, then this zone should have been 
> skipped when checking for compaction_suitable().  In Jim's perf output, 
> compaction_suitable() returns COMPACT_CONTINUE for a transparent hugepage.  
> Why is zone_watermark_ok(zone, 0 low_wmark + 1024, 0, 0) succeeding if 
> isolate_freepages() is going to fail?
> 


zone_watermark_ok doesn't consider migratetype but suitable_migrate_target
does consider one.

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-- 
Kind regards,
Minchan Kim
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