[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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