| From: | Thomas Munro <thomas(dot)munro(at)gmail(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, "Jamison, Kirk" <k(dot)jamison(at)jp(dot)fujitsu(dot)com>, "Tsunakawa, Takayuki" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>, "Ideriha, Takeshi" <ideriha(dot)takeshi(at)jp(dot)fujitsu(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, David Rowley <dgrowleyml(at)gmail(dot)com> |
| Subject: | Re: Cache relation sizes? |
| Date: | 2020-07-31 02:36:12 |
| Message-ID: | CA+hUKGLLGQeM7gW41nf-b6Wcp9t8=ZCO6oaV-FRG53KDyKjA8w@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Sat, Jun 20, 2020 at 10:32 AM Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:
> Rebased. I'll add this to the open commitfest.
I traced the recovery process while running pgbench -M prepared -c16
-j16 -t10000 (= 160,000 transactions). With the patch, the number of
lseeks went from 1,080,661 (6.75 per pgbench transaction) to just 85.
I went ahead and pushed this patch.
There's still the matter of crazy numbers of lseeks in regular
backends; looking at all processes while running the above test, I get
1,469,060 (9.18 per pgbench transaction) without -M prepared, and
193,722 with -M prepared (1.21 per pgbench transaction). Fixing that
with this approach will require bullet-proof shared invalidation, but
I think it's doable, in later work.
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