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help / color / mirror / Atom feedFrom: ravi k <[email protected]>
To: Álvaro Herrera <[email protected]>
Cc: Ramakrishna m <[email protected]>
Cc: pgsql-general <[email protected]>
Subject: Re: Commit Latency
Date: Fri, 7 Feb 2025 18:30:10 +0530
Message-ID: <CAFL4M8FrJqr_VZ4pMu-xNTYA_sg8W=vvrq_d-45zd9nWH7wX1g@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <CAG-eXHLT2Fgw_szi3KUd8a2AE7cgzBsdi3MaUaGb=TQ+w7oV4w@mail.gmail.com>
<[email protected]>
Thanks for the suggestions!
It looks the issue is happening at the time of wal creation, does
wal_init_zero off is good option?
Best
On Wed, 5 Feb, 2025, 9:07 pm Álvaro Herrera, <[email protected]>
wrote:
> Hello
>
> On 2025-Feb-05, Ramakrishna m wrote:
>
> > I have a system handling *300 TPS*, with resource usage *below 10%*.
> > However, I’m noticing *commit latency of around 200ms* for *1% of
> > transactions*, occasionally spiking to *1 second*. Since there is no
> > significant *I/O pressure*, I’m trying to identify what else might be
> > causing this in *PostgreSQL 16*.
>
> max_connections=8000 doesn't sound great -- how many of those are
> active, typically, and how many are idle-in-transaction? And you have
> autovacuum_naptime=5s ... which sounds rather dubious. Either somebody
> with great expertise configured this very carefully, or the settings are
> somewhat randomly chosen with little or no expert oversight. Do you
> have monitoring on the amount of bloat on these database? Maybe you
> should consider connection pooling and limit the number that are active,
> for starters.
>
> Maybe have a look at whether pg_wait_sampling can give you more clues.
> Some basic bloat monitoring is a prerequisite to any further performance
> tweaking anyhow.
>
> --
> Álvaro Herrera Breisgau, Deutschland —
> https://www.EnterpriseDB.com/
> Maybe there's lots of data loss but the records of data loss are also lost.
> (Lincoln Yeoh)
>
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