On Tue, Jul 22, 2025, at 14:48, Joel Jacobson wrote: > Benchmark from original post: ... > For a normal PostgreSQL with the CPU and storage on the same physical machine, > I think the results above clearly demonstrate that the global exclusive lock > is at least not the bottleneck, which I strongly believe instead is the flood > of > unnecessary kill(pid, SIGUSR1) syscalls.
I was wrong here. This is much more complex than I initially thought. After some additional benchmarking and analyzing perf results, I realize the bottleneck depends on the workload, which is either the kill() syscalls *or* the heavyweight lock. Here is one scenario where the heavyweight lock actually *is* the bottleneck: 1 session does LISTEN pgbench -f notify.sql -c 1000 -j 8 -T 60 -n Simply commenting out the heavyweight lock gives a dramatic difference: tps = 7679 (with heavyweight lock; in commit order) tps = 95430 (without heavyweight lock; not in commit order) My conclusion so far is that we would greatly benefit both from reducing/eliminating kill() syscalls, as well as finding ways to avoid the heavyweight lock while preserving commit order. /Joel
