[Linuxppc-users] PostgreSQL support on IBM Power Systems

[Daniel Black]

On Wed, 4 Sep 2019 15:15:11 +0200
Toshaan Bharvani | VanTosh <toshaan at vantosh.com> wrote:

> > A while ago was helping someone out with a potential customer that showed a CPU large usage in postgresql's PinBuffer function but never really got to the bottom of it without a reproducible load with easy access (and whether this was general postgresql tuning problem).  

> Yes, I remember having problems with CPU and memory usage inconsistency,
> this was on a v8 and v9.5 and lower, once we moved to v9.6 all problems
> seem to have been solved.

memory ordering? That sounds about right.


> > So while you have access to multiple instances, are there Postgresql functions that show a higher CPU usage in POWER compared to x86 that I could look optimizing (ahead of potential clients asking)? If so can you show a test case to show it?  
> The only functions/queries we see slower on POWER is the full text
> search , a WHERE LIKE query or tsvector/tsquery function normally does
> very well, however in some cases, we have seen increased CPU and slower
> responses.
> Unfortunately, we have difficulty reproducing theses, so I haven't filed
> any reports, as we do not really understand where the issue could be and
> if it is actually even a Pg issue and not a query issue.

If you work something out or get close I'm interested.

> > Performance data gather with:
> > 
> > perf record -g ; perf report -g --no-children --stdio
> > 
> > Coincidently I'm meeting with 2 postgresql developers next week where I could discuss improvements.
> >   
> I will send you some data by end of the week.

Thanks.

My meetings with postgresql developers is for https://linuxplumbersconf.org/event/4/sessions/60/ and not really about improving performance on POWER. While this would be interesting to discuss please don't put a lot of effort into it expecting it to play a key part in near term improvements.

> If you are working on tests and other improvements, we can always talk
> offline

sure.

> or I can assist with testing, we have multiple architectures.

Thanks.

I've got a few things on the go and this won't get as much attention without client backing, however I hope for a slow improvement of things over a longer time.