Re: Parallel Seq Scan

On 1/23/15 5:42 AM, Amit Kapila wrote:
> *Fixed-Chunks*     
> *No. of workers/Time (ms)*>         *0*     *2*     *4*     *8*     *16*     *24*     *32*
> Run-1     250536     266279     251263     234347     87930     50474     35474
> Run-2     249587     230628     225648     193340     83036     35140     9100
> Run-3     234963     220671     230002     256183     105382     62493     27903
> Run-4     239111     245448     224057     189196     123780     63794     24746
> Run-5     239937     222820     219025     220478     114007     77965     39766
>
>
>
> The trend remains same although there is some variation.
> In block-by-block approach, it performance dips (execution takes
> more time) with more number of workers, though it stabilizes at
> some higher value, still I feel it is random as it leads to random
> scan.
> In Fixed-chunk approach, the performance improves with more
> number of workers especially at slightly higher worker count.

Those fixed chunk numbers look pretty screwy. 2, 4 and 8 workers make no difference, then suddenly 16 cuts times by 1/2
to1/3? Then 32 cuts time by another 1/2 to 1/3?
 
-- 
Jim Nasby, Data Architect, Blue Treble Consulting
Data in Trouble? Get it in Treble! http://BlueTreble.com