| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Parag Paul <parag(dot)paul(at)gmail(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org |
| Subject: | Re: Issue with the PRNG used by Postgres |
| Date: | 2024-04-12 15:45:27 |
| Message-ID: | 20240412154527.us65kyrl5jgvp5ok@awork3.anarazel.de |
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| Lists: | pgsql-hackers |
Hi,
On 2024-04-12 09:43:46 -0400, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > Oh my. There's a workload that completely trivially hits this, without even
> > trying hard. LISTEN/NOTIFY.
>
> Hm. Bug in the NOTIFY logic perhaps?
I don't think it's a bug, async.c:SignalBackends() will signal once for every
NOTIFY, regardless of whether the target has already been signaled. You're
certainly right that:
> Sending that many signals can't be good from a performance POV, whether or
> not it triggers spinlock issues.
I wonder if we could switch this to latches, because with latches we'd only
re-send a signal if the receiving end has already processed the signal. Or
alternatively, make procsignal.c do something similar, although that might
take a bit of work to be done race-free.
Greetings,
Andres Freund
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