Messages in this thread | | | Date | Fri, 06 Nov 2009 15:55:58 +0800 | From | Gui Jianfeng <> | Subject | Re: [PATCH 15/20] blkio: Take care of preemptions across groups |
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Vivek Goyal wrote: > o Additional preemption checks for groups where we travel up the hierarchy > and see if one queue should preempt other or not. > > o Also prevents preemption across groups in some cases to provide isolation > between groups. > > Signed-off-by: Vivek Goyal <vgoyal@redhat.com> > --- > block/cfq-iosched.c | 33 +++++++++++++++++++++++++++++++++ > 1 files changed, 33 insertions(+), 0 deletions(-) > > diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c > index 87b1799..98dbead 100644 > --- a/block/cfq-iosched.c > +++ b/block/cfq-iosched.c > @@ -2636,6 +2636,36 @@ cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq, > } > } > > +static bool cfq_should_preempt_group(struct cfq_data *cfqd, > + struct cfq_queue *cfqq, struct cfq_queue *new_cfqq) > +{ > + struct cfq_entity *cfqe = &cfqq->entity; > + struct cfq_entity *new_cfqe = &new_cfqq->entity; > + > + if (cfqq_to_cfqg(cfqq) != &cfqd->root_group) > + cfqe = parent_entity(&cfqq->entity); > + > + if (cfqq_to_cfqg(new_cfqq) != &cfqd->root_group) > + new_cfqe = parent_entity(&new_cfqq->entity); > + > + /* > + * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice. > + */ > + > + if (new_cfqe->ioprio_class == IOPRIO_CLASS_RT > + && cfqe->ioprio_class != IOPRIO_CLASS_RT) > + return true; > + /* > + * Allow an BE request to pre-empt an ongoing IDLE clas timeslice. > + */ > + > + if (new_cfqe->ioprio_class == IOPRIO_CLASS_BE > + && cfqe->ioprio_class == IOPRIO_CLASS_IDLE) > + return true; > + > + return false; > +} > + > /* > * Check if new_cfqq should preempt the currently active queue. Return 0 for > * no or if we aren't sure, a 1 will cause a preempt. > @@ -2666,6 +2696,9 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, > if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq)) > return true; > > + if (cfqq_to_cfqg(new_cfqq) != cfqq_to_cfqg(cfqq)) > + return cfq_should_preempt_group(cfqd, cfqq, new_cfqq); > +
Vivek, why not put cfq_should_preempt_group() at the beginning of cfq_should_preempt() to prevent preemption across groups?
-- Regards Gui Jianfeng
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