Re: Queries intermittently slow

On 1/7/16 1:47 PM, Andres Freund wrote:
> On 2016-01-07 13:34:51 -0500, Tom Lane wrote:
>> It's fairly well established that the implementation of transparent
>> huge pages in Linux kernels from the 2.6-or-so era sucks, and you're
>> best off turning it off if you care about consistency of performance.
>
> I think the feature wasn't introduced in original 2.6 kernels (3.2 or
> so?), but red hat had backported it to their 2.6.32 kernel.
>
>
>> I am not sure whether modern kernels have improved this area.
>
> I think the problem has largely been solved around 3.16. Around 4.1 I
> could still  reproduce problems, but the regressions were only in the
> sub 10% range in my test workload.

BTW, looks like Scott blogged about this along with some nice graphs:
https://sdwr98.wordpress.com/2016/01/07/transparent-huge-pages-or-why-dbas-are-great/
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Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
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