Hi, On 2021-04-12 12:37:42 -0700, Paul Friedman wrote: > Boiling the complex queries down to their simplest form, we test running 60 > of this query simultaneously: How long does one execution of these queries take (on average)? The likely bottlenecks are very different between running 60 concurrent queries that each complete in 0.1ms and ones that take > 1s. Could you show the results for a query like SELECT state, backend_type, wait_event_type, wait_event, count(*) FROM pg_stat_activity GROUP BY 1, 2, 3, 4 ORDER BY count(*) DESC; ? Without knowing the proportion of LockManager wait events compared to the rest it's hard to know what to make of it. > Does anyone have any advice on how to alleviate LockManager’s LWlock issue? It'd be useful to get a perf profile for this. Both for cpu time and for what ends up blocking on kernel-level locks. E.g. something like # cpu time perf record --call-graph dwarf -F 500 -a sleep 5 perf report --no-children --sort comm,symbol To send it to the list you can use something like perf report --no-children --sort comm,symbol|head -n 500 > somefile # kernel level blocking on locks perf record --call-graph dwarf -e syscalls:sys_enter_futex -a sleep 3 perf report --no-children --sort comm,symbol Greetings, Andres Freund
