| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Peter Geoghegan <pg(at)bowt(dot)ie> |
| Cc: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Claudio Freire <klaussfreire(at)gmail(dot)com>, Anastasia Lubennikova <a(dot)lubennikova(at)postgrespro(dot)ru>, "Andrey V(dot) Lepikhov" <a(dot)lepikhov(at)postgrespro(dot)ru> |
| Subject: | Re: Making all nbtree entries unique by having heap TIDs participate in comparisons |
| Date: | 2019-03-18 23:59:56 |
| Message-ID: | CA+TgmoZCoSw=EZgtkfG7H8Xpa7Ln9wCnovJ+FTFz_BujMmQODA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, Mar 18, 2019 at 7:34 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> With pgbench scale factor 20, here are results for patch and master
> with a Gaussian distribution on my 8 thread/4 core home server, with
> each run reported lasting 10 minutes, repeating twice for client
> counts 1, 2, 8, 16, and 64, patch and master branch:
>
> 1 client master:
> tps = 7203.983289 (including connections establishing)
> 1 client patch:
> tps = 7012.575167 (including connections establishing)
>
> 2 clients master:
> tps = 13434.043832 (including connections establishing)
> 2 clients patch:
> tps = 13105.620223 (including connections establishing)
Blech. I think the patch has enough other advantages that it's worth
accepting that, but it's not great. We seem to keep finding reasons
to reduce single client performance in the name of scalability, which
is often reasonable not but wonderful.
> However, this isn't completely
> free (particularly the page split stuff), and it doesn't pay for
> itself until the number of clients ramps up.
I don't really understand that explanation. It makes sense that more
intelligent page split decisions could require more CPU cycles, but it
is not evident to me why more clients would help better page split
decisions pay off.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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