Re: excessive CPU utilization by isolate_freepages?

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

On Thu, 28 Jun 2012, Minchan Kim wrote:

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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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