From: Heikki Linnakangas <hlinnakangas@vmware.com>
To: pg noob <pgnube@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: deadlock_timeout affect on performance
Date: Tue, 02 Oct 2012 11:11:40 +0300
Message-ID: <506AA1BC.1070305@vmware.com> (raw)
In-Reply-To: <CAPNY-2ULvbcLE9uuTG2=-Zhda+ghW63mPyrBirJ2VQRj=_2TVQ@mail.gmail.com>
References: <CAPNY-2ULvbcLE9uuTG2=-Zhda+ghW63mPyrBirJ2VQRj=_2TVQ@mail.gmail.com>
On 01.10.2012 19:49, pg noob wrote:
> Hi all,
>
> I have a question about the deadlock_timeout in regards to performance.
> Right now we have this timeout set at its default of 1s.
> My understanding of it is that this means that every 1 second the server
> will check for deadlocks.
Not quite. It means that when a backend gets blocked, waiting on a lock,
it will check for deadlocks after waiting for 1 second. When no backend
is waiting for a lock, there are no deadlock checks regardless of
deadlock_timeout.
> What I am wondering is how much of a performance improvement we would
> expect to get if this was raised to 30 seconds?
> Is it negligible or could it be a substantial performance improvement on a
> busy system?
> We very rarely have deadlocks and waiting 30 seconds to discover one
> doesn't seem too bad.
It's almost certainly negligible. If you regularly have deadlocks, it
might even better for performance to make the timeout shorter than 1 s,
so that deadlocks are detected earlier, and backends will spend less
time deadlocked, and more time doing real work. Although I doubt it will
make any meaningful difference either way.
- Heikki
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To: pgsql-performance@postgresql.org
Cc: hlinnakangas@vmware.com, pgnube@gmail.com
Subject: Re: deadlock_timeout affect on performance
In-Reply-To: <506AA1BC.1070305@vmware.com>
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