Re: hugepage compaction causes performance drop

[Aaron Lu <aaron.lu@intel.com>]

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On 11/19/2015 09:29 PM, Vlastimil Babka wrote:
> +CC Andrea, David, Joonsoo
> 
> On 11/19/2015 10:29 AM, Aaron Lu wrote:
>> The vmstat and perf-profile are also attached, please let me know if you
>> need any more information, thanks.
> 
> Output from vmstat (the tool) isn't much useful here, a periodic "cat 
> /proc/vmstat" would be much better.

No problem.

> The perf profiles are somewhat weirdly sorted by children cost (?), but 
> I noticed a very high cost (46%) in pageblock_pfn_to_page(). This could 
> be due to a very large but sparsely populated zone. Could you provide 
> /proc/zoneinfo?

Is a one time /proc/zoneinfo enough or also a periodic one?

> If the compaction scanners behave strangely due to a bug, enabling the 
> ftrace compaction tracepoints should help find the cause. That might 
> produce a very large output, but maybe it would be enough to see some 
> parts of it (i.e. towards beginning, middle, end of the experiment).

I'll see how to do this, never used ftrace before.

Thanks for the quick response.

Regards,
Aaron