From: Sami Imseih <samimseih@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: pgsql-hackers@postgresql.org <pgsql-hackers@postgresql.org>
Subject: Re: Restart pg_usleep when interrupted
Date: Fri, 28 Jun 2024 17:50:20 -0500
Message-ID: <AC328D21-21D6-4FFC-8F6B-BFE9AD940524@gmail.com> (raw)
In-Reply-To: <2100439.1719610468@sss.pgh.pa.us>
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<2100439.1719610468@sss.pgh.pa.us>
Thanks for the feedback!
> On Jun 28, 2024, at 4:34 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> Sami Imseih <samimseih@gmail.com> writes:
>> Reattaching the patch.
>
> I feel like this is fundamentally a wrong solution, for the reasons
> cited in the comment for pg_usleep: long sleeps are a bad idea
> because of the resulting uncertainty about whether we'll respond to
> interrupts and such promptly. An example here is that if we get
> a query cancel interrupt, we should probably not insist on finishing
> out the current sleep before responding.
The case which brought up this discussion is the pg_usleep that
is called within the vacuum_delay_point being interrupted.
When I read the same code comment you cited, it sounded to me
that “long sleeps” are those that are in seconds or minutes. The longest
vacuum delay allowed is 100ms.
> Therefore, rather than "improving" pg_usleep (and uglifying its API),
> the right answer is to fix parallel vacuum leaders to not depend on
> pg_usleep in the first place. A better idea might be to use
> pg_sleep() or equivalent code.
Yes, that is a good idea to explore and it will not require introducing
an awkward new API. I will look into using something similar to
pg_sleep.
Regards,
Sami
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To: pgsql-hackers@postgresql.org
Cc: samimseih@gmail.com, tgl@sss.pgh.pa.us, robertmhaas@gmail.com
Subject: Re: Restart pg_usleep when interrupted
In-Reply-To: <AC328D21-21D6-4FFC-8F6B-BFE9AD940524@gmail.com>
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