Re: tuning postgresql 9.3.5 and multiple cores

On 26/08/14 06:47, Jeison Bedoya Delgado wrote:
> hi, recently i change the hardware of my database 32 cores up to 64
> cores and 128GB Ram, but the performance is the same.  Perhaps i have to
> change any parameter in the postgresql.conf?.
>

In addition to the points that others have made, even if you do have >
32 active sessions it it not clear that 64 cores will automagically get
you twice (or in fact any) better performance than 32. We are seeing
exactly this effect with a (60 core) machine that gets pretty much the
same performance as an older generation 32 core one.

Interestingly while this is *likely* a software issue - it is not
immediately obvious where it lies - we tested Postgres (9.3/9.4/9.5) and
Mysql (5.5/5.6/5.7) *all* of which exhibited the the lack of improvement
with more cores.

Profiling suggested numa effects - but trying to eliminate these seemed
to simply throw up new factors to inhibit performance. My *guess* (and
it is a guess) is that we are seeing 2 (perhaps more) performance
bottlenecks very close to each other: numa and spinlock contention at least.

Regards

Mark