Re: Calculating average block write time - Mailing list pgsql-general

From Laurenz Albe
Subject Re: Calculating average block write time
Date
Msg-id 075d05c6d4cdc01cc2467faded785a1ff77b1395.camel@cybertec.at
Whole thread Raw
In response to Re: Calculating average block write time  (Thomas Kellerer <shammat@gmx.net>)
Responses Re: Calculating average block write time  (Ron <ronljohnsonjr@gmail.com>)
Re: Calculating average block write time  (Thomas Kellerer <shammat@gmx.net>)
List pgsql-general
On Fri, 2022-11-18 at 11:11 +0100, Thomas Kellerer wrote:
> Thomas Kellerer schrieb am 04.11.2022 um 10:19:
> > I can easily calculate the average block read time using
> > pg_stat_database and divide blk_read_time by blks_read.
> > 
> > While there is a column blk_write_time, it seems that there is no
> > cummulative measure for the total number of blocks written.
> > 
> 
> Any ideas on how to get the equivalent of (blk_read_time / blks_read) for blk_write_time?
> 
> I thought about using tup_updated + tup_inserted + tup_deleted because each tuple change would require at least one
blockwritten.
 
> However, a single block write could update multiple tuples so the result of that wouldn't be accurate (too low).

You cannot get that, because most writes are done by the checkpointer, and
that does not distinguish between databases.

Yours,
Laurenz Albe
-- 
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CYBERTEC PostgreSQL International GmbH
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