Re: [Lse-tech] [RFC PATCH] scheduler: Dynamic sched_domains

[Peter Williams <pwil3058@bigpond.net.au>]

Matthew Dobson wrote:
> On Fri, 2004-10-08 at 03:40, Nick Piggin wrote:
> 
>>And so you want to make a partition with CPUs {0,1,2,4,5}, and {3,6,7}
>>for some crazy reason, the new domains would look like this:
>>
>>0 1  2  4 5    3  6 7
>>---  -  ---    -  ---  <- 0
>>  |   |   |     |   |
>>  -----   -     -   -   <- 1
>>    |     |     |   |
>>    -------     -----   <- 2 (global, partitioned)
>>
>>Agreed? You don't need to get fancier than that, do you?
>>
>>Then how to input the partitions... you could have a sysfs entry that
>>takes the complete partition info in the form:
>>
>>0,1,2,3 4,5,6 7,8 ...
>>
>>Pretty dumb and simple.
> 
> 
> How do we describe the levels other than the first?  We'd either need
> to:
> 1) come up with a language to describe the full tree.  For your example
> I quoted above:
>    echo "0,1,2,4,5 3,6 7,8;0,1,2 4,5 3 6,7;0,1 2 4,5 3 6,7" > partitions

I think the idea was that the full hierarchy was (automatically) derived 
from the partition in a way that best matched the physical layout of the 
machine?

> 
> 2) have multiple files:
>    echo "0,1,2,4,5 3,6,7" > level2
>    echo "0,1,2 4,5 3 6,7" > level1
>    echo "0,1 2 4,5 3 6,7" > level0
> 
> 3) Or do it hierarchically as Paul implemented in cpusets, and as I
> described in an earlier mail:
>    mkdir level2
>    echo "0,1,2,4,5 3,6,7" > level2/partitions
>    mkdir level1
>    echo "0,1,2 4,5 3 6,7" > level1/partitions
>    mkdir level0
>    echo "0,1 2 4,5 3 6,7" > level0/partitions
> 
> I personally like the hierarchical idea.  Machine topologies tend to
> look tree-like, and every useful sched_domain layout I've ever seen has
> been tree-like.  I think our interface should match that.
> 
> -Matt
> 
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-- 
Peter Williams                                   pwil3058@bigpond.net.au

"Learning, n. The kind of ignorance distinguishing the studious."
  -- Ambrose Bierce