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    SubjectRe: [PATCH 3/6 v4] cfq-iosched: Introduce vdisktime and io weight for CFQ queue
    Vivek Goyal wrote:
    > On Thu, Feb 10, 2011 at 03:47:16PM +0800, Gui Jianfeng wrote:
    >
    > [..]
    >> +/*
    >> + * The time when a CFQ queue is put onto a service tree is recoreded in
    >> + * cfqq->reposition_time. Currently, we check the first priority CFQ queues
    >> + * on each service tree, and select the workload type that contains the lowest
    >> + * reposition_time CFQ queue among them.
    >> + */
    >> static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
    >> struct cfq_group *cfqg, enum wl_prio_t prio)
    >> {
    >> struct cfq_entity *cfqe;
    >> + struct cfq_queue *cfqq;
    >> + unsigned long lowest_start_time;
    >> int i;
    >> - bool key_valid = false;
    >> - unsigned long lowest_key = 0;
    >> + bool time_valid = false;
    >> enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
    >>
    >> + /*
    >> + * TODO: We may take io priority and io class into account when
    >> + * choosing a workload type. But for the time being just make use of
    >> + * reposition_time only.
    >> + */
    >> for (i = 0; i <= SYNC_WORKLOAD; ++i) {
    >> - /* select the one with lowest rb_key */
    >> cfqe = cfq_rb_first(service_tree_for(cfqg, prio, i));
    >> - if (cfqe &&
    >> - (!key_valid || time_before(cfqe->rb_key, lowest_key))) {
    >> - lowest_key = cfqe->rb_key;
    >> + cfqq = cfqq_of_entity(cfqe);
    >> + if (cfqe && (!time_valid ||
    >> + time_before(cfqq->reposition_time,
    >> + lowest_start_time))) {
    >> + lowest_start_time = cfqq->reposition_time;
    >
    > Gui,
    >
    > Have you had a chance to run some mixed workloads in a group (some sync,
    > some async and some sync-idle queues), and see how latency and throughput
    > of sync-idle workload changes due to this "resposition_time" logic. I
    > just want to make sure that latency of sync-noidle workload does not
    > go up as that's the workload that people care and gets noticed first.

    Hi Vivek

    Will do some tests.

    Thanks,
    Gui

    >
    > Thanks
    > Vivek
    >


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