Horton

Re: Why are wait events not reported even though it reads/writes a timeline history file?

Masahiro Ikeda <ikedamsh@oss.nttdata.com>

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From: Masahiro Ikeda <ikedamsh@oss.nttdata.com>
To: Michael Paquier <michael@paquier.xyz>, Fujii Masao <masao.fujii@oss.nttdata.com>
Cc: pgsql-hackers@postgresql.org
Date: 2020-04-28T08:42:32Z
Lists: pgsql-hackers

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On 2020-04-28 15:09, Michael Paquier wrote:
> On Tue, Apr 28, 2020 at 02:49:00PM +0900, Fujii Masao wrote:
>> Isn't it safer to report the wait event during fgets() rather than 
>> putting
>> those calls around the whole loop, like other code does? For example,
>> writeTimeLineHistory() reports the wait event during read() rather 
>> than
>> whole loop.
> 
> Yeah, I/O wait events should be taken only during the duration of the
> system calls.  Particularly here, you may finish with an elog() that
> causes the wait event to be set longer than it should, leading to a
> rather incorrect state if a snapshot of pg_stat_activity is taken.
> --

Thanks for your comments.

I fixed it to report the wait event during fgets() only.
Please review the v2 patch I attached.

Regard,
-- 
Masahiro Ikeda

Commits

  1. Report missing wait event for timeline history file.