From: Richard Huxton <dev@archonet.com>
To: Wei Weng <wweng@kencast.com>
To: pgsql-sql@postgresql.org
Subject: Re: concurrent connections is worse than serialization?
Date: Wed, 14 Aug 2002 10:18:38 +0100
Message-ID: <200208141018.38875.dev@archonet.com> (raw)
In-Reply-To: <1029271170.16828.7.camel@Monet>
References: <1029271170.16828.7.camel@Monet>
On Tuesday 13 Aug 2002 9:39 pm, Wei Weng wrote:
> I have a testing program that uses 30 concurrent connections
> (max_connections = 32 in my postgresql.conf) and each does 100
> insertions to a simple table with index.
>
> It took me approximately 2 minutes to finish all of them.
>
> But under the same environment(after "delete From test_table, and vacuum
> analyze"), I then queue up all those 30 connections one after another
> one (serialize) and it took only 30 seconds to finish.
>
> Why is it that the performance of concurrent connections is worse than
> serializing them into one?
What was the limiting factor during the test? Was the CPU maxed, memory, disk
I/O?
I take it the insert really *is* simple - no dependencies etc.
> I was testing them using our own (proprietary) scripting engine and the
> extension library that supports postgresql serializes the queries by
> simply locking when a query manipulates a PGconn object and unlocking
> when it is done. (And similiarly, it creates a PGconn object on the
> stack for each concurrent queries.)
I assume you've ruled the application end of things out.
- Richard Huxton
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To: pgsql-sql@postgresql.org
Cc: dev@archonet.com, wweng@kencast.com
Subject: Re: concurrent connections is worse than serialization?
In-Reply-To: <200208141018.38875.dev@archonet.com>
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