From: Jignesh K. Shah <J.K.Shah@Sun.COM>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Scott Carey <scott@richrelevance.com>
Cc: Kevin Grittner <Kevin.Grittner@wicourts.gov>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: Proposal of tunable fix for scalability of 8.4
Date: Wed, 11 Mar 2009 23:48:44 -0400
Message-ID: <49B8861C.2000005@sun.com> (raw)
In-Reply-To: <29836.1236826066@sss.pgh.pa.us>
References: <C5DDBB25.3333%scott@richrelevance.com>
<29836.1236826066@sss.pgh.pa.us>
Tom Lane wrote:
> Scott Carey <scott@richrelevance.com> writes:
>
>> 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.
>> Exclusive locks may be delayed, but will NOT be starved, since on the next iteration, a streak of exclusive locks will occur first in the list and they will all process before any more shared locks can go.
>>
>
> That's a lot of sunny assertions without any shred of evidence behind
> them...
>
> The current LWLock behavior was arrived at over multiple iterations and
> is not lightly to be toyed with IMHO. Especially not on the basis of
> one benchmark that does not reflect mainstream environments.
>
> Note that I'm not saying "no". I'm saying that I want a lot more
> evidence *before* we go to the trouble of making this configurable
> and asking users to test it.
>
> regards, tom lane
>
>
Fair enough.. Well I am now appealing to all who has a fairly decent
sized hardware want to try it out and see whether there are "gains",
"no-changes" or "regressions" based on your workload. Also it will help
if you report number of cpus when you respond back to help collect
feedback.
Regards,
Jignesh
--
Jignesh Shah http://blogs.sun.com/jkshah
The New Sun Microsystems,Inc http://sun.com/postgresql
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To: pgsql-performance@postgresql.org
Cc: J.K.Shah@Sun.COM, tgl@sss.pgh.pa.us, scott@richrelevance.com, Kevin.Grittner@wicourts.gov
Subject: Re: Proposal of tunable fix for scalability of 8.4
In-Reply-To: <49B8861C.2000005@sun.com>
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