| From: | Nathan Bossart <nathandbossart(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Melanie Plageman <melanieplageman(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Stephen Frost <sfrost(at)snowman(dot)net> |
| Subject: | Re: Sub-millisecond [autovacuum_]vacuum_cost_delay broken |
| Date: | 2023-03-09 22:37:47 |
| Message-ID: | 20230309223747.GA3820457@nathanxps13 |
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| Lists: | pgsql-hackers |
On Thu, Mar 09, 2023 at 05:27:08PM -0500, Tom Lane wrote:
> Is it reasonable to assume that all modern platforms can time
> millisecond delays accurately? Ten years ago I'd have suggested
> truncating the delay to a multiple of 10msec and using this logic
> to track the remainder, but maybe now that's unnecessary.
If so, it might also be worth updating or removing this comment in
pgsleep.c:
* NOTE: although the delay is specified in microseconds, the effective
* resolution is only 1/HZ, or 10 milliseconds, on most Unixen. Expect
* the requested delay to be rounded up to the next resolution boundary.
I've had doubts for some time about whether this is still accurate...
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
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