linux-kernel - Re: fair group scheduler not so fair?

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Message-ID: <48360D21.9060102@nortel.com>
Date:	Thu, 22 May 2008 18:17:37 -0600
From:	"Chris Friesen" <cfriesen@...tel.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	"Li, Tong N" <tong.n.li@...el.com>, linux-kernel@...r.kernel.org,
	vatsa@...ux.vnet.ibm.com, mingo@...e.hu, pj@....com
Subject: Re: fair group scheduler not so fair?

Peter Zijlstra wrote:

> Given the following:
> 
>       root
>      / | \
>    _A_ 1  2
>   /| |\
>  3 4 5 B
>       / \
>      6   7
> 
>      CPU0            CPU1
>      root            root
>      /  \            /  \
>     A    1          A    2
>    / \             / \
>   4   B           3   5
>      / \
>     6   7

How do you move specific groups to different cpus.  Is this simply using 
cpusets?

> 
> Numerical examples given the above scenario, assuming every body's
> weight is 1024:

>  s_(0,A) = s_(1,A) = 512

Just to make sure I understand what's going on...this is half of 1024 
because it shows up on both cpus?

>  s_(0,B) = 1024, s_(1,B) = 0

This gets the full 1024 because it's only on one cpu.

>  rw_(0,A) = rw(1,A) = 2048
>  rw_(0,B) = 2048, rw_(1,B) = 0

How do we get 2048?  Shouldn't this be 1024?

>  h_load_(0,A) = h_load_(1,A) = 512
>  h_load_(0,B) = 256, h_load(1,B) = 0

At this point the numbers make sense, but I'm not sure how the formula 
for h_load_ works given that I'm not sure what's going on for rw_.

Chris
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