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SubjectRe: [PATCH 14/24] cfq-iosched: convert cfq_group_slice() to use cfqg->vfraction
On Fri, Dec 28, 2012 at 12:35:36PM -0800, Tejun Heo wrote:
> cfq_group_slice() calculates slice by taking a fraction of
> cfq_target_latency according to the ratio of cfqg->weight against
> service_tree->total_weight. This currently works only because all
> cfqgs are treated to be at the same level.
> To prepare for proper hierarchy support, convert cfq_group_slice() to
> base the calculation on cfqg->vfraction. As cfqg->vfraction is always
> a fraction of 1 and represents the fraction allocated to the cfqg with
> hierarchy considered, the slice can be simply calculated by
> multiplying cfqg->vfraction to cfq_target_latency (with fixed point
> shift factored in).
> As vfraction calculation currently treats all non-root cfqgs as
> children of the root cfqg, this patch doesn't introduce noticeable
> behavior difference.
> Signed-off-by: Tejun Heo <>

Acked-by: Vivek Goyal <>


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