| From: | Sami Imseih <samimseih(at)gmail(dot)com> |
|---|---|
| To: | Nathan Bossart <nathandbossart(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andres Freund <andres(at)anarazel(dot)de>, Bertrand Drouvot <bertranddrouvot(dot)pg(at)gmail(dot)com>, Rahila Syed <rahilasyed90(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Improve LWLock tranche name visibility across backends |
| Date: | 2025-08-26 00:37:05 |
| Message-ID: | CAA5RZ0uYpXw8yTpCPiDAvwt9WtXesKM_vebbCjBm4MQBVnchMw@mail.gmail.com |
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| Lists: | pgsql-hackers |
> On Mon, Aug 25, 2025 at 04:59:41PM -0500, Sami Imseih wrote:
> > hmm, can we really avoid a shared lock when reading from shared memory?
> > considering access for both reads and writes can be concurrent to shared
> > memory. We are also taking an exclusive lock when writing a new tranche.
>
> We probably want to hold a lock while we 1) increment LWLockCounter and
> copy a new tranche name to memory and
In the last rev, I removed the spinlock acquired on ShmemLock in-lieu of
a LWLock. This is because I wanted a single LWLock acquisition while
both incrementing LWLockCounter and writing to shared memory, and
doing this much work, particularly writing to shared memory,
with a spinlock seemed inappropriate. With that said, this is not high
concurrency of performance sensitive activity at all, so perhaps I was
being overly paranoid.
--
Sami
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