Re: Should we cacheline align PGXACT? - Mailing list pgsql-hackers

From Robert Haas
Subject Re: Should we cacheline align PGXACT?
Date
Msg-id 7503E425-6651-4D40-83FD-592AF580D618@gmail.com
Whole thread Raw
In response to Should we cacheline align PGXACT?  (Alexander Korotkov <a.korotkov@postgrespro.ru>)
Responses Re: Should we cacheline align PGXACT?  (Tom Lane <tgl@sss.pgh.pa.us>)
Re: Should we cacheline align PGXACT?  (Andres Freund <andres@anarazel.de>)
List pgsql-hackers
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


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