From: Kevin Grittner <Kevin.Grittner@wicourts.gov>
To: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
To: Scott Carey <scott@richrelevance.com>
To: Jignesh K. Shah <J.K.Shah@Sun.COM>
Subject: Re: Proposal of tunable fix for scalability of 8.4
Date: Thu, 12 Mar 2009 10:13:24 -0500
Message-ID: <49B8E044.EE98.0025.0@wicourts.gov> (raw)
In-Reply-To: <C5DDBB25.3333%scott@richrelevance.com>
References: <49B7F470.EE98.0025.0@wicourts.gov>
<C5DDBB25.3333%scott@richrelevance.com>
>>> Scott Carey <scott@richrelevance.com> wrote:
> "Kevin Grittner" <Kevin.Grittner@wicourts.gov> wrote:
>
>> I'm a lot more interested in what's happening between 60 and 180
>> than over 1000, personally. If there was a RAID involved, I'd put
>> it down to better use of the numerous spindles, but when it's all
>> in RAM it makes no sense.
>
> If there is enough lock contention and a common lock case is a short
> lived shared lock, it makes perfect sense sense. Fewer readers are
> blocked waiting on writers at any given time. Readers can 'cut' in
> line ahead of writers within a certain scope (only up to the number
> waiting at the time a shared lock is at the head of the queue).
> Essentially this clumps up shared and exclusive locks into larger
> streaks, and allows for higher shared lock throughput.
You misunderstood me. I wasn't addressing the affects of his change,
but rather the fact that his test shows a linear improvement in TPS up
to 1000 connections for a 64 thread machine which is dealing entirely
with RAM -- no disk access. Where's the bottleneck that allows this
to happen? Without understanding that, his results are meaningless.
-Kevin
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To: pgsql-performance@postgresql.org
Cc: Kevin.Grittner@wicourts.gov, scott@richrelevance.com, J.K.Shah@Sun.COM
Subject: Re: Proposal of tunable fix for scalability of 8.4
In-Reply-To: <49B8E044.EE98.0025.0@wicourts.gov>
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