Hi, On 2019-02-19 12:52:08 +1300, David Rowley wrote: > On Tue, 19 Feb 2019 at 12:42, Tom Lane <t...@sss.pgh.pa.us> wrote: > > My own thought about how to improve this situation was just to destroy > > and recreate LockMethodLocalHash at transaction end (or start) > > if its size exceeded $some-value. Leaving it permanently bloated seems > > like possibly a bad idea, even if we get rid of all the hash_seq_searches > > on it. > > That seems like a good idea. Although, it would be good to know that > it didn't add too much overhead dropping and recreating the table when > every transaction happened to obtain more locks than $some-value. If > it did, then maybe we could track the average locks per of recent > transactions and just ditch the table after the locks are released if > the locks held by the last transaction exceeded the average * > 1.something. No need to go near shared memory to do that.
Isn't a large portion of benefits in this patch going to be mooted by the locking improvements discussed in the other threads? I.e. there's hopefully not going to be a ton of cases with low overhead where we acquire a lot of locks and release them very soon after. Sure, for DDL etc we will, but I can't see this mattering from a performance POV? I'm not against doing something like Tom proposes, but heuristics with magic constants like this tend to age purely / are hard to tune well across systems. Greetings, Andres Freund
