Re: Straightforward changes for increased SMP scalability

Joshua D. Drake wrote:
> Gregory Stark wrote:
>> "Joshua D. Drake" <jd@commandprompt.com> writes:
>>
>>> +1 on the idea (I can speak to the technical side). What I can say 
>>> is that it
>>> is pretty much known that after 8 cores we slow down. Although 8.2 
>>> is better
>>> than any other release in this regard.
>>
>> Wait, what benchmarks have you seen where we slow down? 
>
> The production type. :)
>
> Hmm maybe that is a bad way to put it. I am not saying we slow down 
> like we move slower than before. I mean per processor performance goes 
> down. If I have 4 Cores things rock and roll. If I have 8 cores (and 
> obvious sufficient workload) things rock and roll louder than 4 cores.
>
> If I have 16 cores, things are still really loud but I start to not be 
> able to tell the difference. The percentage of improvement is much lower.
>
> E.g, 16 cores works and PostgreSQL work great, but it is not nearly as 
> fantastic with 16 cores as 8 cores (in terms percentage gain).
>
>
>
>

That's not the same thing as slowing down, it just means that scaling 
isn't always linear, which isn't surprising.

cheers

andrew