| From: | Nathan Bossart <nathandbossart(at)gmail(dot)com> |
|---|---|
| To: | Sami Imseih <samimseih(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: | 2025-08-25 21:04:56 |
| Message-ID: | aKzP-H-KzPay-ByM@nathan |
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| Lists: | pgsql-hackers |
On Fri, Aug 22, 2025 at 03:01:53PM -0500, Sami Imseih wrote:
> I kept the local array to serve consecutive reads and to avoid having to
> take a shared lock on shared memory every time GetLWTrancheName is
> called. A new LWLock to protect this array is required.
I'm not seeing why we need this cache anymore. This is an append-only
list, so we could instead keep a backend-local copy of LWLockCounter that
gets updated as needed. As long as the ID is less than our backend-local
counter, we can go straight to the shared array. If it is greater, we'll
have to first update our counter, which should be rare and inexpensive.
--
nathan
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