| 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: | 2025-08-25 21:59:41 |
| Message-ID: | CAA5RZ0vWh2uxG99iUb3P4nsoDLk0x7Yuai83AbbGs3YZvJM8QQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
> On Mon, Aug 25, 2025 at 04:37:21PM -0500, Sami Imseih wrote:
> > When we lookup from shared array only, we need to take a shared lock
> > every lookup. Acquiring that lock is what I am trying to avoid. You
> > are saying it's not worth optimizing that part, correct?
>
> Why do we need a shared lock here? IIUC there's no chance that existing
> entries will change. We'll only ever add new ones to the end.
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.
--
Sami
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