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SubjectRe: [PATCH UPDATED 15/24] cfq-iosched: enable full blkcg hierarchy support
On Mon, Jan 07, 2013 at 08:34:05AM -0800, Tejun Heo wrote:

[..]
> + weight leaf_weight
> + root : 125 125
> + A : 500 750
> + B : 250 500
> + AA : 500 500
> + AB : 1000 500
> +
> +root never has a parent making its weight is meaningless. For backward
> +compatibility, weight is always kept in sync with leaf_weight. B, AA
> +and AB have no child and thus its tasks have no children cgroup to
> +compete with. They always get 100% of what the cgroup won at the
> +parent level. Considering only the weights which matter, the hierarchy
> +looks like the following.
> +
> + root
> + / | \
> + A B leaf
> + 500 250 125
> + / | \
> + AA AB leaf
> + 500 1000 750
> +
> +If all cgroups have active IOs and competing with each other, disk
> +time will be distributed like the following.
> +
> +Distribution below root. The total active weight at this level is
> +A:500 + B:250 + C:125 = 875.
> +
> + root-leaf : 125 / 875 =~ 14%
> + A : 500 / 875 =~ 57%
> + B(-leaf) : 250 / 875 =~ 28%
> +
> +A has children and further distributes its 57% among the children and
> +the implicit leaf node. The total active weight at this level is
> +AA:500 + AB:1000 + A-leaf:750 = 2250.
> +
> + A-leaf : ( 750 / 2250) * A =~ 19%
> + AA(-leaf) : ( 500 / 2250) * A =~ 12%
> + AB(-leaf) : (1000 / 2250) * A =~ 25%

Hi Tejun,

What does (-leaf) is supposed to signify? I can understand that A-leaf
tells the share of A's tasks which are effectively in A-leaf group.

Will just plain AA and AB be more clear?

Rest looks good to me. Thanks for updating the blkio-controoler.txt too.

Thanks
Vivek


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