Message-Id: <49B8E79C.EE98.0025.0@wicourts.gov>
Date: Thu, 12 Mar 2009 10:44:44 -0500
From: "Kevin Grittner" <Kevin.Grittner@wicourts.gov>
To: "=?ISO-8859-15?Q?Grzegorz=20Ja*kiewicz?=" <gryzman@gmail.com>
Cc: "pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>,
	"Scott Carey" <scott@richrelevance.com>,
	"Jignesh K. Shah" <J.K.Shah@sun.com>
Subject: Re: Proposal of tunable fix for scalability of 8.4
References: <49B7F470.EE98.0025.0@wicourts.gov>
	<C5DDBB25.3333%scott@richrelevance.com>
	<49B8E044.EE98.0025.0@wicourts.gov>
	<2f4958ff0903120831q4ca3d0a8o8f2571f16b316ecf@mail.gmail.com>
In-Reply-To: <2f4958ff0903120831q4ca3d0a8o8f2571f16b316ecf@mail.gmail.com>
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>>> Grzegorz Ja½kiewicz <gryzman@gmail.com> wrote: 
> Scalability is something that is affected by everything, and fixing
> this makes sens as much as looking at possible fixes to make raids
> more scalable, which is looked at by someone else I think.
> So please, don't say that this doesn't make sense because he tested
it
> against ram disc. That was precisely the point of exercise.
 
I'm probably more inclined to believe that his change may have merit
than many here, but I can't accept anything based on this test until
someone answers the question, so far ignored by all responses, of
where the bottleneck is at the low end which allows linear scalability
up to 1000 users (which I assume means connections).
 
I'm particularly inclined to be suspicious of this test since my own
benchmarks, with real applications replaying real URL requests from a
production website that gets millions of hits per day, show that
response time and throughput are improved by using a connection pool
with queuing to limit the concurrent active queries.
 
My skepticism is not helped by the fact that in a previous discussion
with someone about performance as connections are increased, this
point was covered by introducing a "primitive" connection pool --
which used a one second sleep for a thread if the maximum number of
connections were already in use, rather than proper queuing and
semaphores.  That really gives no clue how performance would be with a
real connection pool.
 
-Kevin