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authorTejun Heo <tj@kernel.org>2013-01-09 08:05:11 -0800
committerTejun Heo <tj@kernel.org>2013-01-09 08:05:11 -0800
commit41cad6ab2cb9ccb3b11546ad56b8b285e47c6279 (patch)
treec6308080ab464a5f7a5da52035e948431061949a /Documentation/block
parent1d3650f713e7f6392b02fde450c5bae40291e65b (diff)
cfq-iosched: convert cfq_group_slice() to use cfqg->vfraction
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 <tj@kernel.org> Acked-by: Vivek Goyal <vgoyal@redhat.com>
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