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    Subject[PATCH 6/15] cfq-iosched: sort RT queues into the rbtree
    Date
    Currently CFQ does a linked insert into the current list for RT
    queues. We can just factor the class into the rb insertion,
    and then we don't have to treat RT queues in a special way. It's
    faster, too.

    Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
    ---
    block/cfq-iosched.c | 27 ++++++++++++---------------
    1 files changed, 12 insertions(+), 15 deletions(-)
    diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
    index 7f964ee..38ac492 100644
    --- a/block/cfq-iosched.c
    +++ b/block/cfq-iosched.c
    @@ -471,7 +471,16 @@ static void cfq_service_tree_add(struct cfq_data *cfqd,
    parent = *p;
    __cfqq = rb_entry(parent, struct cfq_queue, rb_node);

    - if (rb_key < __cfqq->rb_key)
    + /*
    + * sort RT queues first, we always want to give
    + * preference to them. after that, sort on the next
    + * service time.
    + */
    + if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq))
    + p = &(*p)->rb_left;
    + else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq))
    + p = &(*p)->rb_right;
    + else if (rb_key < __cfqq->rb_key)
    p = &(*p)->rb_left;
    else {
    p = &(*p)->rb_right;
    @@ -490,7 +499,6 @@ static void cfq_service_tree_add(struct cfq_data *cfqd,
    static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
    {
    struct cfq_data *cfqd = cfqq->cfqd;
    - struct list_head *n;

    /*
    * Resorting requires the cfqq to be on the RR list already.
    @@ -500,25 +508,14 @@ static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)

    list_del_init(&cfqq->cfq_list);

    - if (cfq_class_rt(cfqq)) {
    - /*
    - * At to the front of the current list, but behind other
    - * RT queues.
    - */
    - n = &cfqd->cur_rr;
    - while (n->next != &cfqd->cur_rr)
    - if (!cfq_class_rt(cfqq))
    - break;
    -
    - list_add(&cfqq->cfq_list, n);
    - } else if (cfq_class_idle(cfqq)) {
    + if (cfq_class_idle(cfqq)) {
    /*
    * IDLE goes to the tail of the idle list
    */
    list_add_tail(&cfqq->cfq_list, &cfqd->idle_rr);
    } else {
    /*
    - * So we get here, ergo the queue is a regular best-effort queue
    + * RT and BE queues, sort into the rbtree
    */
    cfq_service_tree_add(cfqd, cfqq);
    }
    --
    1.5.1.1.190.g74474
    -
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