Re: Lock contention high

Hi,
Yes, lock contention reduced with postgresqlv14.
Lock acquire reduced 18% to 10%
10.49 %postgres postgres [.] LWLockAcquire
5.09% postgres postgres [.] _bt_compare

Is lock contention can be reduced to 0-3%?
On pg-stat-activity shown LwLock as “BufferCounter” and “WalInsert”

On Tuesday, October 26, 2021, Andres Freund <andres(at)anarazel(dot)de> wrote:

> Hi,
>
> On 2021-10-12 13:05:12 +0530, Ashkil Dighin wrote:
> > PostgreSQL version: 13.3
>
> You could try postgres 14 - that did improve scalability in some areas.
>
>
>
> > Perf data for 24vu(TPC-C)
> > --------------------------------
> >
> > 18.99% postgres postgres [.] LWLockAcquire
> > 7.09% postgres postgres [.] _bt_compare
> > 8.66% postgres postgres [.] LWLockRelease
> > 2.28% postgres postgres [.] GetSnapshotData
> > 2.25% postgres postgres [.] hash_search_with_hash_value
> > 2.11% postgres postgres [.] XLogInsertRecord
> > 1.98% postgres postgres [.] PinBuffer
>
> To be more useful you'd need to create a profile with 'caller' information
> using 'perf record --call-graph dwarf', and then check what the important
> callers are.
>
>
> > Postgres.conf used in Baremetal
> > ========================
> > shared_buffers = 128GB(1/4 th RAM size)
> > effective_cachesize=392 GB(1/3 or 75% of RAM size)
>
> If your hot data set is actually larger than s_b, I'd recommend trying a
> larger s_b. It's plausible that a good chunk of lock contention is from
> that.
>
> Greetings,
>
> Andres Freund
>