Re: Lock contention high

On Tue, Oct 12, 2021 at 01:05:12PM +0530, Ashkil Dighin wrote:
> Hi,
> Lock contention observed high in PostgreSQLv13.3
> The source code compiled with GNC(GCCv11.x)
> PostgreSQL version: 13.3
> Operating system: RHEL8.3
> Kernel name:4.18.0-305.10.2.el8_4.x86_64
> RAM Size:512GB
> SSD: 1TB
> The environment used IBM metal and test benchmark environment HammerDbv4.2
> Test case :TPC-C
>
> Perf data for 24vu(TPC-C)
> --------------------------------
>
> 18.99% postgres postgres [.] LWLockAcquire
> 7.09% postgres postgres [.] _bt_compare
> 8.66% postgres postgres [.] LWLockRelease
...
> 1.Is there a way to tune the lock contention ?
> 2.Is any recommendations to tune/reduce the lock contention via postgres.conf

I think you'd want to find *which* LW locks are being waited on, to see if it's
something that can be easily tuned.

You can check pg_stat_activity, or maybe create a cronjob to record its content
for later analysis.

--
Justin