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Re: Performance under contention

From: Jignesh Shah <jkshah(at)gmail(dot)com>
To: Ivan Voras <ivoras(at)freebsd(dot)org>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Performance under contention
Date: 2010-11-22 06:54:50
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
On Sun, Nov 21, 2010 at 9:18 PM, Ivan Voras <ivoras(at)freebsd(dot)org> wrote:
> On 11/22/10 02:47, Kevin Grittner wrote:
>> Ivan Voras  wrote:
>>> After 16 clients (which is still good since there are only 12
>>> "real" cores in the system), the performance drops sharply
>> Yet another data point to confirm the importance of connection
>> pooling.  :-)
> I agree, connection pooling will get rid of the symptom. But not the
> underlying problem. I'm not saying that having 1000s of connections to the
> database is a particularly good design, only that there shouldn't be a sharp
> decline in performance when it does happen. Ideally, the performance should
> remain the same as it was at its peek.
> I've been monitoring the server some more and it looks like there are
> periods where almost all servers are in the semwait state followed by
> periods of intensive work - approximately similar to the "thundering herd"
> problem, or maybe to what Josh Berkus has posted a few days ago.
> --
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Try it with systemtap or dtrace and see if you find the same
bottlenecks as I do in

I will probably retry it with pgBench and see what  I find ..


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