From: Robert Haas <robertmhaas@gmail.com>
To: Jignesh K. Shah <J.K.Shah@sun.com>
Cc: Alvaro Herrera <alvherre@commandprompt.com>
Cc: Scott Carey <scott@richrelevance.com>
Cc: Greg Smith <gsmith@gregsmith.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: Fri, 20 Mar 2009 20:45:28 -0400
Message-ID: <603c8f070903201745m575642f5s539e1a374ce4ce9f@mail.gmail.com> (raw)
In-Reply-To: <49C42921.8050508@sun.com>
References: <603c8f070903191349p5e8fb00as2816581d584fcefd@mail.gmail.com>
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<20090320154601.GC8313@alvh.no-ip.org>
<20090320215813.GR8313@alvh.no-ip.org>
<20090320220513.GS8313@alvh.no-ip.org>
<49C42921.8050508@sun.com>
On Fri, Mar 20, 2009 at 7:39 PM, Jignesh K. Shah <J.K.Shah@sun.com> wrote:
> Alvaro Herrera wrote:
>>> So Simon's correct.
>> And perhaps this explains why Jignesh is measuring an improvement on his
>> benchmark. Perhaps an useful experiment would be to turn this behavior
>> off and compare performance. This lack of measurement is probably the
>> cause that the suggested patch to fix it was never applied.
>>
>> The patch is here
>> http://archives.postgresql.org//pgsql-hackers/2004-11/msg00935.php
>
> One of the reasons why my patch helps is it keeps this check intact but
> allows other exclusive Wake up.. Now what PostgreSQL calls "Wakes" is in
> reality just makes a variable indicating wake up and not really signalling a
> process to wake up. This is a key point to note. So when the process wanting
> the exclusive fights the OS Scheduling policy to finally get time on the CPU
> then it check the value to see if it is allowed to wake up and potentially
I'm confused. Is a process waiting for an LWLock is in a runnable
state? I thought we went to sleep on a semaphore.
...Robert
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To: pgsql-performance@postgresql.org
Cc: robertmhaas@gmail.com, J.K.Shah@sun.com, alvherre@commandprompt.com, scott@richrelevance.com, gsmith@gregsmith.com, Kevin.Grittner@wicourts.gov
Subject: Re: Proposal of tunable fix for scalability of 8.4
In-Reply-To: <603c8f070903201745m575642f5s539e1a374ce4ce9f@mail.gmail.com>
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