Re: Improve LWLock tranche name visibility across backends

Hi,

On Sat, Aug 30, 2025 at 09:14:46AM -0500, Nathan Bossart wrote:
> On Fri, Aug 29, 2025 at 09:51:38PM -0500, Nathan Bossart wrote:
> > I've also attached a rebased patch that addresses all the latest feedback.
> > A reworked verison of the test patch is also included, but that's mostly
> > intended for CI purposes and is still not intended for commit (yet).
>
> And here's an attempt at fixing the alignment problems revealed by cfbot.

Indeed:

==24409==Using libbacktrace symbolizer.
../src/backend/storage/lmgr/lwlock.c:441:31: runtime error: store to misaligned address 0x7f7644188904 for type 'char *', which requires 8 byte alignment

Changes look good.

Not directly related, but I think that we can get rid of:

size = add_size(size, LWLOCK_PADDED_SIZE);

in LWLockShmemSize() and of:

ptr += LWLOCK_PADDED_SIZE - ((uintptr_t) ptr) % LWLOCK_PADDED_SIZE;

in CreateLWLocks(), and just make use of CACHELINEALIGN().

Attached, a patch doing so. It applies on top of your v20.

Regards,

--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
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