On 03/12/2025 02:47, Andres Freund wrote:
> On 2025-11-25 11:54:00 -0500, Andres Freund wrote:
>> Thanks a lot for that detailed review! A few questions and comments, before I
>> try to address the comments in the next version.
>
> Here's that new new version, with the following changes
>
> - Some more micro-optimizations, most importantly adding a commit that doesn't
> initialize the delay in LockBufHdr() unless needed. With those I don't see a
> consistent slowdown anymore (slight speedup on one workstation, slight
> slowdown on another, in an absurdly adverse workload)
+1
I'm comparing the patched LockBufHdr() with LWLockWaitListLock(), which
does pretty much the same thing, and LWLockWaitListLock() already did
the initialization of the delay that way. But there are some small
differences:
- LockBufHdr() uses unlikely() in the initial attempt,
LWLockWaitListLock() does not
- LWLockWaitListLock() uses pg_atomic_read_u32() after spinning,
LockBufHdr() retries directly with pg_atomic_fetch_or_u32().
Are there reasons for the differences, or is it just that they were
developed separately and ended up looking slightly different?
- Heikki
