pgsql-hackers-owner@postgresql.org wrote on 04/03/2017 01:58:03 PM:
> From: Andres Freund <andres@anarazel.de> > To: Alexander Korotkov <a.korotkov@postgrespro.ru> > Cc: David Steele <david@pgmasters.net>, Ashutosh Sharma > <ashu.coek88@gmail.com>, Simon Riggs <simon@2ndquadrant.com>, Alvaro > Herrera <alvherre@2ndquadrant.com>, Robert Haas > <robertmhaas@gmail.com>, Bernd Helmle <mailings@oopsware.de>, Tomas > Vondra <tomas.vondra@2ndquadrant.com>, pgsql-hackers <pgsql- > hackers@postgresql.org> > Date: 04/03/2017 01:59 PM > Subject: Re: [HACKERS] Should we cacheline align PGXACT? > Sent by: pgsql-hackers-owner@postgresql.org > > On 2017-03-25 19:35:35 +0300, Alexander Korotkov wrote: > > On Wed, Mar 22, 2017 at 12:23 AM, David Steele <david@pgmasters.net> wrote: > > > > > Hi Alexander > > > > > > On 3/10/17 8:08 AM, Alexander Korotkov wrote: > > > > > > Results look good for me. Idea of committing both of patches looks > > >> attractive. > > >> We have pretty much acceleration for read-only case and small > > >> acceleration for read-write case. > > >> I'll run benchmark on 72-cores machine as well. > > >> > > > > > > Have you had a chance to run those tests yet? > > > > > > > I discovered an interesting issue. > > I found that ccce90b3 (which was reverted) gives almost same effect as > > PGXACT alignment on read-only test on 72-cores machine. > > That's possibly because it changes alignment? > > > > That shouldn't be related to the functionality of ccce90b3 itself, because > > read-only test don't do anything with clog. And that appears to be true. > > Padding of PGPROC gives same positive effect as ccce90b3. Padding patch > > (pgproc-pad.patch) is attached. It's curious that padding changes size of > > PGPROC from 816 bytes to 848 bytes. So, size of PGPROC remains 16-byte > > aligned. So, probably effect is related to distance between PGPROC > > members... > > > > See comparison of 16-bytes alignment of PGXACT + reduce PGXACT access vs. > > padding of PGPROC. > > My earlier testing had showed that padding everything is the best > approach :/ > My approach has been to, generally, pad "everything" as well. In my testing on power, I padded PGXACT to 16 bytes. To my surprise, with the padding in isolation, the performance (on hammerdb) was slightly degraded.
Jim Van Fleet > > I'm inclined to push this to the next CF, it seems we need a lot more > benchmarking here. > > Greetings, > > Andres Freund > > > -- > Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-hackers >
