From: Robert Haas <robertmhaas@gmail.com>
To: drvillo <f.vivoli@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Checkpoint execution overrun impact?
Date: Wed, 11 May 2011 23:36:19 -0400
Message-ID: <BANLkTikFUqMuC6Xrt7kd91FKTzXCCAT7MQ@mail.gmail.com> (raw)
In-Reply-To: <1303464095907-4332601.post@n5.nabble.com>
References: <1303464095907-4332601.post@n5.nabble.com>
On Fri, Apr 22, 2011 at 5:21 AM, drvillo <f.vivoli@gmail.com> wrote:
> -given the configuration attached (which is basically a vanilla one) and the
> number of buffers written at each execution, are these execution times
> normal or above average?
They seem fine. Remember that the write is deliberately spread out;
it's not as if the system couldn't write out 130-160 8k blocks in less
than 30 s.
> -in the case of the execution that overruns past the timeout, what are the
> implications wrt the client application?
Not sure what you are referring to here.
> -AFAIU client connections are basically stalled during checkpoints. Is it
> reasonable to infer that the fact that the application blocking on a
> getConnection() might be related to checkpoints being executed?
> -considering some tuning on the PG side, should I try increasing
> checkpoint_timeout and rising checkpoint_completion_target to lessen the
> impact of IO on the client or should I shorten the period so there's less
> stuff to write? from the number of buffers written on average I'd assume the
> first option is the one to go for but I might miss some bit of reasoning
> here...
I'm a bit puzzled by all of this because the logs you posted seem to
reflect a system under very light load. Each checkpoint is writing no
more than 4% of shared_buffers and the sync phases are generally
completing in less than one second. I don't see why that would be
causing stalls.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: robertmhaas@gmail.com, f.vivoli@gmail.com
Subject: Re: Checkpoint execution overrun impact?
In-Reply-To: <BANLkTikFUqMuC6Xrt7kd91FKTzXCCAT7MQ@mail.gmail.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox