Horton

Re: SLRU statistics

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Fujii Masao <masao.fujii@oss.nttdata.com>
Cc: Tomas Vondra <tomas.vondra@2ndquadrant.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Masahiko Sawada <masahiko.sawada@2ndquadrant.com>, "tsunakawa.takay@fujitsu.com" <tsunakawa.takay@fujitsu.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2020-05-14T18:52:06Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Fix async.c to not register any SLRU stats counts in the postmaster.

  2. Use proper GetDatum function in pg_stat_get_slru().

  3. Initialize SLRU stats entries to zero.

  4. Remove pg_xact from pg_stat_reset_slru docs

  5. Remove pg_xact entry from SLRU stats

  6. Track SLRU page hits in SimpleLruReadPage_ReadOnly

  7. Fix typo in SLRU stats documentation

  8. Collect statistics about SLRU caches

  9. Simplify and rename some GUC variables, per various recent discussions:

On Thu, May 14, 2020 at 2:27 AM Fujii Masao <masao.fujii@oss.nttdata.com> wrote:
> Therefore what we can do right now seems to make checkpointer report the SLRU
> stats while it's running. Other issues need more time to investigate...
> Thought?

I'm confused by why SLRU statistics are reported by messages sent to
the stats collector rather than by just directly updating shared
memory. For database or table statistics there can be any number of
objects and we can't know in advance how many there will be, so we
can't set aside shared memory for the stats in advance. For SLRUs,
there's no such problem. Just having the individual backends
periodically merge their accumulated backend-local counters into the
shared counters seems like it would be way simpler and more
performant.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company