Re: [PATCH 14/16] blkio: Idle on a group for some time on rotational media

Corrado Zoccolo
2009-11-13T10:58:53Z

Hi Vivek,
On Fri, Nov 13, 2009 at 12:32 AM, Vivek Goyal <vgoyal@redhat.com> wrote:
> o If a group is not continuously backlogged, then it will be deleted from
>  service tree and loose it share. For example, if a single random seeky
>  reader or a single sequential reader is running in group.
>
Without groups, a single sequential reader would already have its 10ms
idle slice, and a single random reader on the noidle service tree
would have its 2ms idle, before switching to a new workload. Were
those removed in the previous patches (and this patches re-enable
them), or this introduces an additional idle between groups?

> o One solution is to let group loose it share if it is not backlogged and
>  other solution is to wait a bit for the slow group so that it can get its
>  time slice. This patch implements waiting for a group to wait a bit.
>
> o This waiting is disabled for NCQ SSDs.
>
> o This patch also intorduces the tunable "group_idle" which can enable/disable
>  group idling manually.
>
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>

Thanks,
Corrado