[PATCH 11/23] io-controller: Introduce group idling
Rik van Riel
riel at redhat.com
Sat Aug 29 17:38:20 PDT 2009
Vivek Goyal wrote:
> o It is not always that IO from a process or group is continuous. There are
> cases of dependent reads where next read is not issued till previous read
> has finished. For such cases, CFQ introduced the notion of slice_idle,
> where we idle on the queue for sometime hoping next request will come
> and that's how fairness is provided otherwise queue will be deleted
> immediately from the service tree and this process will not get the
> fair share.
> o This patch introduces the similar concept at group level. Idle on the group
> for a period of "group_idle" which is tunable through sysfs interface. So
> if a group is empty and about to be deleted, we idle for the next request.
> o This patch also introduces the notion of wait busy where we wait for one
> extra group_idle period even if queue has consumed its time slice. The
> reason being that group will loose its share upon removal from service
> tree as some other entity will be picked for dispatch and vtime jump will
> take place.
> Signed-off-by: Vivek Goyal <vgoyal at redhat.com>
Acked-by: Rik van Riel <riel at redhat.com>
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