Re: Proposal of tunable fix for scalability of 8.4

From: Scott Carey <scott(at)richrelevance(dot)com>
To: Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, "david(at)lang(dot)hm" <david(at)lang(dot)hm>, Kevin Grittner <Kgrittn(dot)CCAP(dot)Courts(at)wicourts(dot)gov>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Greg Smith <gsmith(at)gregsmith(dot)com>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Jignesh K(dot) Shah" <J(dot)K(dot)Shah(at)sun(dot)com>
Subject: Re: Proposal of tunable fix for scalability of 8.4
Date: 2009-03-16 18:44:34
Message-ID: C5E3EC22.3580%scott@richrelevance.com
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Note, some have mentioned that my client breaks inline formatting. My only comment is after Kevin's signature below:

On 3/16/09 9:53 AM, "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> wrote:

I wrote:
> One more reason this point is an interesting one is that it is one
> that gets *worse* with the suggested patch, if only by half a
percent.
>
> Without:
>
> 600: 80: Medium Throughput: 82632.000 Avg Medium Resp: 0.005
>
> with:
>
> 600: 80: Medium Throughput: 82241.000 Avg Medium Resp: 0.005

Oops. A later version:

> Redid the test with - waking up all waiters irrespective of shared,
> exclusive

> 600: 80: Medium Throughput: 82920.000 Avg Medium Resp: 0.005

The one that showed the decreased performance at 800 was:

> a modified Fix (not the original one that I proposed but something
> that works like a heart valve : Opens and shuts to minimum
> default way thus controlling how many waiters are waked up )

-Kevin

All three of those are probably within the margin of error of the measurement. We would need to run the same test 3 or 4 times to gauge its variance before concluding much.

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