Re: Quantify small changes to predicate evaluation

On Tue, Jun 17, 2014 at 10:23 AM, Dennis Butterstein <soullinuxer@web.de> wrote:
> Hi Marti, thank you for your quick reply. I tried the proposed tweaks and
> see some differences regarding the measurements. It seems as if the overall
> query performance dropped a little what I think the disabled turbo boost
> mode is responsible for (all measurements are single query only). I think
> that kind of behaviour is somewhat expected. Run1: 26.559s Run2: 28.280s
> Unfortunately the variance between the runs seems to remain high. In fact I
> have exclusive access to the machine and I made sure not to run in any i/o
> related problems regarding buffer caches. Are there any other stumbling
> blocks I'm missing at the moment? Maybe I've to rethink my (end-to-end)
> measurement strategy. In your experience how small is it possible to get
> measurement variances on Postgres? Thank you very much. Kind regards, Dennis

I find that it's possible to get smaller variations than what you're
experiencing on read-only workloads without any special tuning, but
variation on workloads that write data is much higher, similar to what
you're seeing.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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