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    Subject[PATCH 03/21] blkio: Implement macro to traverse each idle tree in group
    Date
    o Implement a macro to traverse each service tree in the group. This avoids
    usage of double for loop and special condition for idle tree 4 times.

    o Macro is little twisted because of special handling of idle class service
    tree.

    Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
    ---
    block/cfq-iosched.c | 35 +++++++++++++++++++++--------------
    1 files changed, 21 insertions(+), 14 deletions(-)

    diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
    index 3baa3f4..c73ff44 100644
    --- a/block/cfq-iosched.c
    +++ b/block/cfq-iosched.c
    @@ -303,6 +303,15 @@ CFQ_CFQQ_FNS(deep);
    #define cfq_log(cfqd, fmt, args...) \
    blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)

    +/* Traverses through cfq group service trees */
    +#define for_each_cfqg_st(cfqg, i, j, st) \
    + for (i = 0; i < 3; i++) \
    + for (j = 0, st = i < 2 ? &cfqg->service_trees[i][j] : \
    + &cfqg->service_tree_idle; \
    + (i < 2 && j < 3) || (i == 2 && j < 1); \
    + j++, st = i < 2 ? &cfqg->service_trees[i][j]: NULL) \
    +
    +
    static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
    {
    if (cfq_class_idle(cfqq))
    @@ -565,6 +574,10 @@ cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2,
    */
    static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
    {
    + /* Service tree is empty */
    + if (!root->count)
    + return NULL;
    +
    if (!root->left)
    root->left = rb_first(&root->rb);

    @@ -1592,18 +1605,14 @@ static int cfq_forced_dispatch(struct cfq_data *cfqd)
    int dispatched = 0;
    int i, j;
    struct cfq_group *cfqg = &cfqd->root_group;
    + struct cfq_rb_root *st;

    - for (i = 0; i < 2; ++i)
    - for (j = 0; j < 3; ++j)
    - while ((cfqq = cfq_rb_first(&cfqg->service_trees[i][j]))
    - != NULL)
    - dispatched += __cfq_forced_dispatch_cfqq(cfqq);
    -
    - while ((cfqq = cfq_rb_first(&cfqg->service_tree_idle)) != NULL)
    - dispatched += __cfq_forced_dispatch_cfqq(cfqq);
    + for_each_cfqg_st(cfqg, i, j, st) {
    + while ((cfqq = cfq_rb_first(st)) != NULL)
    + dispatched += __cfq_forced_dispatch_cfqq(cfqq);
    + }

    cfq_slice_expired(cfqd, 0);
    -
    BUG_ON(cfqd->busy_queues);

    cfq_log(cfqd, "forced_dispatch=%d", dispatched);
    @@ -2974,6 +2983,7 @@ static void *cfq_init_queue(struct request_queue *q)
    struct cfq_data *cfqd;
    int i, j;
    struct cfq_group *cfqg;
    + struct cfq_rb_root *st;

    cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
    if (!cfqd)
    @@ -2981,11 +2991,8 @@ static void *cfq_init_queue(struct request_queue *q)

    /* Init root group */
    cfqg = &cfqd->root_group;
    -
    - for (i = 0; i < 2; ++i)
    - for (j = 0; j < 3; ++j)
    - cfqg->service_trees[i][j] = CFQ_RB_ROOT;
    - cfqg->service_tree_idle = CFQ_RB_ROOT;
    + for_each_cfqg_st(cfqg, i, j, st)
    + *st = CFQ_RB_ROOT;

    /*
    * Not strictly needed (since RB_ROOT just clears the node and we
    --
    1.6.2.5


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