Re: Should we cacheline align PGXACT?

On Aug 19, 2016, at 2:12 AM, Alexander Korotkov <a.korotkov@postgrespro.ru> wrote:
> Hackers,
>
> originally this idea was proposed by Andres Freund while experimenting with lockfree Pin/UnpinBuffer [1].
> The patch is attached as well as results of pgbench -S on 72-cores machine.  As before it shows huge benefit in this
case.
> For sure, we should validate that it doesn't cause performance regression in other cases.  At least we should test
read-writeand smaller machines. 
> Any other ideas?

Wow, nice results.  My intuition on why PGXACT helped in the first place was that it minimized the number of cache
linesthat had to be touched to take a snapshot. Padding obviously would somewhat increase that again, so I can't quite
understandwhy it seems to be helping... any idea? 

...Robert