On Sun, Feb 23, 2025 at 4:16 AM Andres Freund <and...@anarazel.de> wrote: > We do count the number of lwlock share lockers and the number of buffer > refcounts within those bits. And obviously 0 lockers/refcounts has to be > valid. So I think the limit is correct?
Ah, right. That makes perfect sense. The 18 bits need to be able to hold a count, not just an index, and I confused myself about that from the moment I thought about the name PROC_NUMBER_BITS, which I retract. > I didn't yet have enough coffe, but isn't the inval.c limit 2^24-1 rather than > 2^23-1? Yeah, it has 24 bits of space, but curiously backend_hi is signed, so (msg->sm.backend_hi << 16) would be sign-extended, so it wouldn't actually work if you used all 24 bits... which is obviously not a real problem...
