Horton

Re: Improve LWLock tranche name visibility across backends

Nathan Bossart <nathandbossart@gmail.com>

View thread View on postgr.es
From: Nathan Bossart <nathandbossart@gmail.com>
To: Sami Imseih <samimseih@gmail.com>
Cc: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2025-07-15T16:57:31Z
Lists: pgsql-hackers 
On Tue, Jul 15, 2025 at 11:52:19AM -0500, Sami Imseih wrote:
>> Another random thought: I worry that the dshash approach might be quite a
>> bit slower, and IIUC we just need to map an integer to a string.  Maybe we
>> should just use a DSA for LWLockTrancheNames. IOW we'd leave it as a char**
>> but put it in shared memory.
> 
> To use DSA just for this purpose, we would need to maintain an array of
> dsa_pointers that reference the string(s), right? I am not clear what you
> mean by using dsa to put the char**

I was imagining putting the array in one big DSA allocation instead of
carting around a pointer for each tranche name.  (Sorry, I realize I am
hand-waving over some of the details.)

-- 
nathan

Commits

  1. test_dsa: Avoid leaking LWLock tranches.

  2. Teach DSM registry to ERROR if attaching to an uninitialized entry.

  3. Add a test harness for the LWLock tranche code.

  4. Revert recent change to RequestNamedLWLockTranche().

  5. Move dynamically-allocated LWLock tranche names to shared memory.

  6. Prepare DSM registry for upcoming changes to LWLock tranche names.

  7. Add GetNamedDSA() and GetNamedDSHash().