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Date: Sun, 14 Oct 2012 12:47:21 +0300
From: Andriy Gapon <avg@FreeBSD.org>
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Subject: Re: new DragonFly-3.2 scheduler and PostgreSQL comparision with
 FreeBSD 9.1-RC1
References: <CAJ-VmomzubLrG7apd2tFObo2C_C2J4jRanwdR6foY-x3wcRSuA@mail.gmail.com>
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on 14/10/2012 00:27 Pedro Giffuni said the following:
> Actually ...
> 
> On 10/13/2012 13:38, Jakub Lach wrote:
>> I'm not at all up to date with DragonFly, so does anybody know
>> what did they change so spectacularly between 3.0/3.2?
>>
> Their explanation of the changes is here:
> 
> http://www.shiningsilence.com/dbsdlog/2012/09/19/10403.html

>From the article:

      (3) It will detect process block/wakeup events which e.g. tie two
	  processes together, and will try to move the process pairs closer
	  to each other using that information.

	  For example, if you have many postgres clients and servers on a
	  large server, enough to load down all cores, the client and
	  server pairs will be localized to the same socket, thus making
	  use of chip caches to facilitate communications between the two
	  processes.

This sounds like a nice heuristic.  Currently our code unintentionally does the
opposite quite often.

-- 
Andriy Gapon