| From: | Jim Nasby <Jim(dot)Nasby(at)BlueTreble(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Rick Otten <rottenwindfish(at)gmail(dot)com>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Queries intermittently slow |
| Date: | 2016-01-07 21:04:33 |
| Message-ID: | 568ED2E1.6060107@BlueTreble.com |
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| Lists: | pgsql-performance |
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/
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com
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