public inbox for pgsql-hackers@postgresql.org
help / color / mirror / Atom feedFrom: Andres Freund <andres@anarazel.de>
To: Jelte Fennema-Nio <postgres@jeltef.nl>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: torikoshia <torikoshia@oss.nttdata.com>
Cc: pgsql-hackers@postgresql.org
Cc: rjuju123@gmail.com
Cc: Bruce Momjian <bruce@momjian.us>
Subject: Re: RFC: Allow EXPLAIN to Output Page Fault Information
Date: Tue, 11 Feb 2025 10:36:55 -0500
Message-ID: <3gz6ymrgnua75aviagsl4d4traoqxo2g2rzzykqa3yl4jyts3y@gj6lcc6aziil> (raw)
In-Reply-To: <CAGECzQTQ+QxR3__5vrHoAoKHs8Uv+c=ZY3_o1FsvXXx4AaRJJQ@mail.gmail.com>
References: <CAGECzQRvcLx44N3zd_DGCjY02XX4AqXX8mq4BiS8C9Froy+Jhg@mail.gmail.com>
<CAGECzQQdc-k=M2fMCKa98kVZntc=6d3rpd6edt8Qs45cayfUeQ@mail.gmail.com>
<myw76agwrlmisvamwbfl6ibxgwh5glzitydiwnfmtb5aui232i@274yxxtnbnsp>
<2035079.1739124342@sss.pgh.pa.us>
<CAGECzQTm6oEEY4yO_FO0ZBtUuJX+pYiXhw2GPPRMzq_5DP5_fQ@mail.gmail.com>
<edvo7bpgi7rcthj7btsduleep4j6dcnsx3a2aqrwmybetttmkw@g5chr66cckg6>
<CAGECzQTydZ33miLd=KdbfrV17RowRGBwQrS28hZ0i6+YhetYgg@mail.gmail.com>
<mzjytadtjqv4knvwukppaol5zx2qzt2bkuqvjlo4rjawvhn4ql@qmdf64qkmxjo>
<dfnb7me4hsbdb6mxlosxcfvh4xjdk5qoy42piuu2ahblwmocyf@ma3bh552myoe>
<CAGECzQTQ+QxR3__5vrHoAoKHs8Uv+c=ZY3_o1FsvXXx4AaRJJQ@mail.gmail.com>
Hi,
On 2025-02-11 09:59:43 +0100, Jelte Fennema-Nio wrote:
> On Tue, 11 Feb 2025 at 00:53, Andres Freund <andres@anarazel.de> wrote:
> > > The thing is that you'd often get completely misleading stats. Some of the IO
> > > will still be done by the backend itself, so there will be a non-zero
> > > value. But it will be a significant undercount, because the asynchronously
> > > executed IO won't be tracked (if worker mode is used).
>
> Yeah, makes sense. Like I said, I would be completely fine with not
> showing these numbers at all/setting them to 0 for setups where we
> cannot easily get useful numbers (and this bgworker AIO would be one
> of those setups).
Shrug. It means that it'll not work in what I hope will be the default
mechanism before long. I just can't get excited for that. In all likelihood
it'll result in bug reports that I'll then be on the hook to fix.
> > Independent to of this, it's probably not good that we're tracking shared
> > buffer hits after io combining, if I interpret this correctly... That looks to
> > be an issue in master, not just the AIO branch.
>
> You mean that e.g. a combined IO for 20 blocks still sounds only as 1
> "shared read"? Yeah, that sounds like a bug.
Yep.
Greetings,
Andres Freund
reply
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-hackers@postgresql.org
Cc: andres@anarazel.de, postgres@jeltef.nl, tgl@sss.pgh.pa.us, torikoshia@oss.nttdata.com, rjuju123@gmail.com, bruce@momjian.us
Subject: Re: RFC: Allow EXPLAIN to Output Page Fault Information
In-Reply-To: <3gz6ymrgnua75aviagsl4d4traoqxo2g2rzzykqa3yl4jyts3y@gj6lcc6aziil>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox