Hi, On 2021-01-19 14:16:07 +0800, Craig Ringer wrote: > AFAICS it'd be necessary to expand PROCLOG to expose this in shmem. > Probably by adding a small bitfield where bit 0 is set if there's a txn > level lock and bit 1 is set if there's a session level lock. But I'm not > convinced that expanding PROCLOCK is justifiable for this. sizeof(PROCLOCK) > is 64 on a typical x64 machine. Adding anything to it increases it to 72 > bytes.
Indeed - I really don't want to increase the size, it's already a problem. > It's frustrating to be unable to tell the difference between session-level > and txn-level locks in diagnostic output. It'd be useful, I agree. > And the deadlock detector has no way to tell the difference when > selecting a victim for a deadlock abort - it'd probably make sense to > prefer to send a deadlock abort for txn-only lockers. I'm doubtful this is worth going for. > But I'm not sure I see a sensible way to add the info - PROCLOCK is > already free of any padding, and I wouldn't want to use hacks like > pointer-tagging. I think there's an easy way to squeeze out space: make groupLeader be an integer index into allProcs instead. That requires only 4 bytes... Alternatively, I think it'd be reasonably easy to add the scope as a bit in LOCKMASK - there's plenty space. Greetings, Andres Freund
