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From: Nazir Bilal Yavuz <byavuz81@gmail.com>
Date: Tue, 17 Sep 2024 14:52:01 +0300
Message-ID: <CAN55FZ0_0Fj6No-axtDF-jrPQKh6a-qLoU73mpSAG417D+A-NA@mail.gmail.com>
Subject: Re: per backend I/O statistics
To: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, 
	pgsql-hackers@lists.postgresql.org
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Hi,

On Fri, 13 Sept 2024 at 19:09, Bertrand Drouvot
<bertranddrouvot.pg@gmail.com> wrote:
> On Fri, Sep 13, 2024 at 04:45:08PM +0300, Nazir Bilal Yavuz wrote:
> > - The pgstat_reset_io_counter_internal() is called in the
> > pgstat_shutdown_hook(). This causes the stats_reset column showing the
> > termination time of the old backend when its proc num is reassigned to
> > a new backend.
>
> doh! Nice catch, thanks!
>
> And also new backends that are not re-using a previous "existing" process slot
> are getting the last reset time (if any). So the right place to fix this is in
> pgstat_io_init_backend_cb(): done in v4 attached. v4 also sets the reset time to
> 0 in pgstat_shutdown_hook() (but that's not necessary though, that's just to be
> right "conceptually" speaking).

Thanks, I confirm that it is fixed.

You mentioned some refactoring upthread:

On Fri, 6 Sept 2024 at 18:03, Bertrand Drouvot
<bertranddrouvot.pg@gmail.com> wrote:
>
> - If we agree on the current proposal then I'll do  some refactoring in
> pg_stat_get_backend_io(), pg_stat_get_my_io() and pg_stat_get_io() to avoid
> duplicated code (it's not done yet to ease the review).

Could we remove pg_stat_get_my_io() completely and use
pg_stat_get_backend_io() with the current backend's pid to get the
current backend's stats? If you meant the same thing, please don't
mind it.

-- 
Regards,
Nazir Bilal Yavuz
Microsoft