Re: Relation extension scalability

On Thu, Mar 31, 2016 at 10:29 AM, Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:

>
> On Tue, Mar 29, 2016 at 10:08 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
> wrote:
>
>> Yes, that makes sense. One more point is that if the reason for v13
>> giving better performance is extra blocks (which we believe in certain
>> cases can leak till the time Vacuum updates the FSM tree), do you think it
>> makes sense to once test by increasing lockWaiters * 20 limit to may
>> be lockWaiters * 25 or lockWaiters * 30.
>
>
> I tested COPY 10000 record, by increasing the number of blocks just to
> find out why we are not as good as V13
> with extraBlocks = Min( lockWaiters * 40, 2048) and got below results..
>
> COPY 10000
> --------------------
> Client Patch(extraBlocks = Min( lockWaiters * 40, 2048))
> -------- ---------
> 16 752
> 32 708
>
> This proves that main reason of v13 being better is its adding extra
> blocks without control.
> though v13 is better than these results, I think we can get that also by
> changing multiplier and max limit .
>
> But I think we are ok with the max size as 4MB (512 blocks) right?.
>
>
This shows that there is performance increase of ~26% (599 to 752) at 16
client count if we raise the limit of max extend size from 4MB to 16MB
which is a good boost, but not sure if it is worth extending the relation
for cases where the newly added pages won't get used. I think it should be
okay to go for 4MB as a limit for now and then if during beta testing or in
future, there are use cases where tuning this max limit helps, then we can
come back to it.

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com