Horton

Re: SLRU statistics

Fujii Masao <masao.fujii@oss.nttdata.com>

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From: Fujii Masao <masao.fujii@oss.nttdata.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>, Tomas Vondra <tomas.vondra@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: 2020-05-14T02:18:53Z
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 2020/05/14 2:44, Tom Lane wrote:
> I wrote:
>>>> (IIRC only the Async module is doing that.)
> 
>> Hm, maybe we can fix that.
> 
> Yeah, it's quite easy to make async.c postpone its first write to the
> async SLRU.  This seems like a win all around, because many installations
> don't use NOTIFY and so will never need to do that work at all.  In
> installations that do use notify, this costs an extra instruction or
> two per NOTIFY, but that's down in the noise.

Looks good to me. Thanks for the patch!

> I got through check-world with the assertion shown that we are not
> counting any SLRU operations in the postmaster.  Don't know if we
> want to commit that or not --- any thoughts?

+1 to add this assertion because basically it's not good thing
to access to SLRU at postmaster and we may want to fix that if found.
At least if we get rid of the SLRUStats initialization code,
IMO it's better to add this assertion and ensure that postmaster
doesn't update the SLRU stats counters.

Regards,

-- 
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION