Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=6d048f5310aa2dda2b5acd947eab3598c25e269f
Commit:     6d048f5310aa2dda2b5acd947eab3598c25e269f
Parent:     1e3335de05da3dfbe48b8caa03db1834a2133256
Author:     Jens Axboe <[EMAIL PROTECTED]>
AuthorDate: Wed Apr 25 12:44:27 2007 +0200
Committer:  Jens Axboe <[EMAIL PROTECTED]>
CommitDate: Mon Apr 30 09:01:21 2007 +0200

    cfq-iosched: development update
    
    - Implement logic for detecting cooperating processes, so we
      choose the best available queue whenever possible.
    
    - Improve residual slice time accounting.
    
    - Remove dead code: we no longer see async requests coming in on
      sync queues. That part was removed a long time ago. That means
      that we can also remove the difference between cfq_cfqq_sync()
      and cfq_cfqq_class_sync(), they are now indentical. And we can
      kill the on_dispatch array, just make it a counter.
    
    - Allow a process to go into the current list, if it hasn't been
      serviced in this scheduler tick yet.
    
    Possible future improvements including caching the cfqq lookup
    in cfq_close_cooperator(), so we don't have to look it up twice.
    cfq_get_best_queue() should just use that last decision instead
    of doing it again.
    
    Signed-off-by: Jens Axboe <[EMAIL PROTECTED]>
---
 block/cfq-iosched.c |  381 +++++++++++++++++++++++++++++++++++----------------
 1 files changed, 261 insertions(+), 120 deletions(-)

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index bfb3967..28236f2 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -56,13 +56,7 @@ static struct completion *ioc_gone;
 #define ASYNC                  (0)
 #define SYNC                   (1)
 
-#define cfq_cfqq_dispatched(cfqq)      \
-       ((cfqq)->on_dispatch[ASYNC] + (cfqq)->on_dispatch[SYNC])
-
-#define cfq_cfqq_class_sync(cfqq)      ((cfqq)->key != CFQ_KEY_ASYNC)
-
-#define cfq_cfqq_sync(cfqq)            \
-       (cfq_cfqq_class_sync(cfqq) || (cfqq)->on_dispatch[SYNC])
+#define cfq_cfqq_sync(cfqq)    ((cfqq)->key != CFQ_KEY_ASYNC)
 
 #define sample_valid(samples)  ((samples) > 80)
 
@@ -79,6 +73,7 @@ struct cfq_data {
        struct list_head busy_rr;
        struct list_head cur_rr;
        struct list_head idle_rr;
+       unsigned long cur_rr_tick;
        unsigned int busy_queues;
 
        /*
@@ -98,11 +93,12 @@ struct cfq_data {
        struct cfq_queue *active_queue;
        struct cfq_io_context *active_cic;
        int cur_prio, cur_end_prio;
+       unsigned long prio_time;
        unsigned int dispatch_slice;
 
        struct timer_list idle_class_timer;
 
-       sector_t last_sector;
+       sector_t last_position;
        unsigned long last_end_request;
 
        /*
@@ -117,6 +113,9 @@ struct cfq_data {
        unsigned int cfq_slice_idle;
 
        struct list_head cic_list;
+
+       sector_t new_seek_mean;
+       u64 new_seek_total;
 };
 
 /*
@@ -133,6 +132,8 @@ struct cfq_queue {
        unsigned int key;
        /* member of the rr/busy/cur/idle cfqd list */
        struct list_head cfq_list;
+       /* in what tick we were last serviced */
+       unsigned long rr_tick;
        /* sorted list of pending requests */
        struct rb_root sort_list;
        /* if fifo isn't expired, next request to serve */
@@ -148,10 +149,11 @@ struct cfq_queue {
 
        unsigned long slice_end;
        unsigned long service_last;
+       unsigned long slice_start;
        long slice_resid;
 
-       /* number of requests that are on the dispatch list */
-       int on_dispatch[2];
+       /* number of requests that are on the dispatch list or inside driver */
+       int dispatched;
 
        /* io prio of this group */
        unsigned short ioprio, org_ioprio;
@@ -159,6 +161,8 @@ struct cfq_queue {
 
        /* various state flags, see below */
        unsigned int flags;
+
+       sector_t last_request_pos;
 };
 
 enum cfqq_state_flags {
@@ -259,6 +263,8 @@ cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue 
*cfqq)
         * easily introduce oscillations.
         */
        cfqq->slice_resid = 0;
+
+       cfqq->slice_start = jiffies;
 }
 
 /*
@@ -307,7 +313,7 @@ cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, 
struct request *rq2)
        s1 = rq1->sector;
        s2 = rq2->sector;
 
-       last = cfqd->last_sector;
+       last = cfqd->last_position;
 
        /*
         * by definition, 1KiB is 2 sectors
@@ -398,39 +404,42 @@ cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue 
*cfqq,
        return cfq_choose_req(cfqd, next, prev);
 }
 
-static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
+/*
+ * This function finds out where to insert a BE queue in the service hierarchy
+ */
+static void cfq_resort_be_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq,
+                               int preempted)
 {
-       struct cfq_data *cfqd = cfqq->cfqd;
        struct list_head *list, *n;
        struct cfq_queue *__cfqq;
+       int add_tail = 0;
 
        /*
-        * Resorting requires the cfqq to be on the RR list already.
+        * if cfqq has requests in flight, don't allow it to be
+        * found in cfq_set_active_queue before it has finished them.
+        * this is done to increase fairness between a process that
+        * has lots of io pending vs one that only generates one
+        * sporadically or synchronously
         */
-       if (!cfq_cfqq_on_rr(cfqq))
-               return;
-
-       list_del(&cfqq->cfq_list);
-
-       if (cfq_class_rt(cfqq))
+       if (cfqq->dispatched)
+               list = &cfqd->busy_rr;
+       else if (cfqq->ioprio == (cfqd->cur_prio + 1) &&
+                cfq_cfqq_sync(cfqq) &&
+                (time_before(cfqd->prio_time, cfqq->service_last) ||
+                 cfq_cfqq_queue_new(cfqq) || preempted)) {
                list = &cfqd->cur_rr;
-       else if (cfq_class_idle(cfqq))
-               list = &cfqd->idle_rr;
-       else {
+               add_tail = 1;
+       } else
+               list = &cfqd->rr_list[cfqq->ioprio];
+
+       if (!cfq_cfqq_sync(cfqq) || add_tail) {
                /*
-                * if cfqq has requests in flight, don't allow it to be
-                * found in cfq_set_active_queue before it has finished them.
-                * this is done to increase fairness between a process that
-                * has lots of io pending vs one that only generates one
-                * sporadically or synchronously
+                * async queue always goes to the end. this wont be overly
+                * unfair to writes, as the sort of the sync queue wont be
+                * allowed to pass the async queue again.
                 */
-               if (cfq_cfqq_dispatched(cfqq))
-                       list = &cfqd->busy_rr;
-               else
-                       list = &cfqd->rr_list[cfqq->ioprio];
-       }
-
-       if (preempted || cfq_cfqq_queue_new(cfqq)) {
+               list_add_tail(&cfqq->cfq_list, list);
+       } else if (preempted || cfq_cfqq_queue_new(cfqq)) {
                /*
                 * If this queue was preempted or is new (never been serviced),
                 * let it be added first for fairness but beind other new
@@ -444,14 +453,7 @@ static void cfq_resort_rr_list(struct cfq_queue *cfqq, int 
preempted)
 
                        n = n->next;
                }
-               list_add_tail(&cfqq->cfq_list, n);
-       } else if (!cfq_cfqq_class_sync(cfqq)) {
-               /*
-                * async queue always goes to the end. this wont be overly
-                * unfair to writes, as the sort of the sync queue wont be
-                * allowed to pass the async queue again.
-                */
-               list_add_tail(&cfqq->cfq_list, list);
+               list_add(&cfqq->cfq_list, n);
        } else {
                /*
                 * sort by last service, but don't cross a new or async
@@ -461,17 +463,54 @@ static void cfq_resort_rr_list(struct cfq_queue *cfqq, 
int preempted)
                 */
                n = list;
                while ((n = n->prev) != list) {
-                       struct cfq_queue *__cfqq = list_entry_cfqq(n);
+                       struct cfq_queue *__c = list_entry_cfqq(n);
 
-                       if (!cfq_cfqq_class_sync(cfqq) || !__cfqq->service_last)
+                       if (!cfq_cfqq_sync(__c) || !__c->service_last)
                                break;
-                       if (time_before(__cfqq->service_last, 
cfqq->service_last))
+                       if (time_before(__c->service_last, cfqq->service_last))
                                break;
                }
                list_add(&cfqq->cfq_list, n);
        }
 }
 
+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.
+        */
+       if (!cfq_cfqq_on_rr(cfqq))
+               return;
+
+       list_del(&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)) {
+               /*
+                * 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
+                */
+               cfq_resort_be_queue(cfqd, cfqq, preempted);
+       }
+}
+
 /*
  * add to busy list of queues for service, trying to be fair in ordering
  * the pending list according to last request service
@@ -579,6 +618,8 @@ static void cfq_activate_request(request_queue_t *q, struct 
request *rq)
         */
        if (!cfqd->hw_tag && cfqd->rq_in_driver > 4)
                cfqd->hw_tag = 1;
+
+       cfqd->last_position = rq->hard_sector + rq->hard_nr_sectors;
 }
 
 static void cfq_deactivate_request(request_queue_t *q, struct request *rq)
@@ -684,6 +725,7 @@ __cfq_set_active_queue(struct cfq_data *cfqd, struct 
cfq_queue *cfqq)
                cfq_clear_cfqq_must_alloc_slice(cfqq);
                cfq_clear_cfqq_fifo_expire(cfqq);
                cfq_mark_cfqq_slice_new(cfqq);
+               cfqq->rr_tick = cfqd->cur_rr_tick;
        }
 
        cfqd->active_queue = cfqq;
@@ -786,10 +828,46 @@ static int cfq_get_next_prio_level(struct cfq_data *cfqd)
                cfqd->cur_end_prio = 0;
        }
 
+       cfqd->cur_rr_tick++;
+       cfqd->prio_time = jiffies;
        return prio;
 }
 
-static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
+static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
+                                         struct request *rq)
+{
+       if (rq->sector >= cfqd->last_position)
+               return rq->sector - cfqd->last_position;
+       else
+               return cfqd->last_position - rq->sector;
+}
+
+static struct cfq_queue *cfq_get_best_queue(struct cfq_data *cfqd)
+{
+       struct cfq_queue *cfqq = NULL, *__cfqq;
+       sector_t best = -1, dist;
+
+       list_for_each_entry(__cfqq, &cfqd->cur_rr, cfq_list) {
+               if (!__cfqq->next_rq || !cfq_cfqq_sync(__cfqq))
+                       continue;
+
+               dist = cfq_dist_from_last(cfqd, __cfqq->next_rq);
+               if (dist < best) {
+                       best = dist;
+                       cfqq = __cfqq;
+               }
+       }
+
+       /*
+        * Only async queue(s) available, grab first entry
+        */
+       if (!cfqq)
+               cfqq = list_entry_cfqq(cfqd->cur_rr.next);
+
+       return cfqq;
+}
+
+static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
 {
        struct cfq_queue *cfqq = NULL;
 
@@ -799,7 +877,7 @@ static struct cfq_queue *cfq_set_active_queue(struct 
cfq_data *cfqd)
                 * empty, get next prio level and grab first entry then if any
                 * are spliced
                 */
-               cfqq = list_entry_cfqq(cfqd->cur_rr.next);
+               cfqq = cfq_get_best_queue(cfqd);
        } else if (!list_empty(&cfqd->busy_rr)) {
                /*
                 * If no new queues are available, check if the busy list has
@@ -820,49 +898,128 @@ static struct cfq_queue *cfq_set_active_queue(struct 
cfq_data *cfqd)
                        mod_timer(&cfqd->idle_class_timer, end);
        }
 
+       return cfqq;
+}
+
+static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
+{
+       struct cfq_queue *cfqq;
+
+       do {
+               long prio;
+
+               cfqq = cfq_get_next_queue(cfqd);
+               if (!cfqq)
+                       break;
+
+               prio = cfq_prio_to_slice(cfqd, cfqq);
+               if (cfqq->slice_resid > -prio)
+                       break;
+
+               cfqq->slice_resid += prio;
+               list_del_init(&cfqq->cfq_list);
+               list_add_tail(&cfqq->cfq_list, &cfqd->rr_list[cfqq->ioprio]);
+               cfqq = NULL;
+       } while (1);
+
        __cfq_set_active_queue(cfqd, cfqq);
        return cfqq;
 }
 
-#define CIC_SEEKY(cic) ((cic)->seek_mean > (128 * 1024))
+static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq)
+{
+       struct cfq_io_context *cic = cfqd->active_cic;
+
+       if (!sample_valid(cic->seek_samples))
+               return 0;
+
+       return cfq_dist_from_last(cfqd, rq) <= cic->seek_mean;
+}
+
+static struct cfq_queue *__cfq_close_cooperator(struct cfq_data *cfqd,
+                                               struct cfq_queue *cur_cfqq,
+                                               struct list_head *list)
+{
+       struct cfq_queue *cfqq;
+
+       list_for_each_entry(cfqq, list, cfq_list) {
+               if (cfqq == cur_cfqq || !cfq_cfqq_sync(cfqq))
+                       continue;
+
+               BUG_ON(!cfqq->next_rq);
+
+               if (cfq_rq_close(cfqd, cfqq->next_rq))
+                       return cfqq;
+       }
+
+       return NULL;
+}
+
+static int cfq_close_cooperator(struct cfq_data *cfqd,
+                               struct cfq_queue *cur_cfqq)
+{
+       struct cfq_queue *cfqq;
+
+       if (!cfqd->busy_queues)
+               return 0;
+
+       /*
+        * check cur_rr and same-prio rr_list for candidates
+        */
+       cfqq = __cfq_close_cooperator(cfqd, cur_cfqq, &cfqd->cur_rr);
+       if (cfqq)
+               return 1;
+
+       cfqq = __cfq_close_cooperator(cfqd, cur_cfqq, 
&cfqd->rr_list[cur_cfqq->ioprio]);
+       if (cfqq && (cfqq->rr_tick == cfqd->cur_rr_tick))
+               cfqq = NULL;
+
+       return cfqq != NULL;
+}
+
+#define CIC_SEEKY(cic) ((cic)->seek_mean > (8 * 1024))
 
-static int cfq_arm_slice_timer(struct cfq_data *cfqd)
+static void cfq_arm_slice_timer(struct cfq_data *cfqd)
 {
        struct cfq_queue *cfqq = cfqd->active_queue;
        struct cfq_io_context *cic;
        unsigned long sl;
 
        WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
+       WARN_ON(cfq_cfqq_slice_new(cfqq));
 
        /*
         * idle is disabled, either manually or by past process history
         */
-       if (!cfqd->cfq_slice_idle)
-               return 0;
-       if (!cfq_cfqq_idle_window(cfqq))
-               return 0;
+       if (!cfqd->cfq_slice_idle || !cfq_cfqq_idle_window(cfqq))
+               return;
+
        /*
         * task has exited, don't wait
         */
        cic = cfqd->active_cic;
        if (!cic || !cic->ioc->task)
-               return 0;
+               return;
+
+       /*
+        * See if this prio level has a good candidate
+        */
+       if (cfq_close_cooperator(cfqd, cfqq))
+               return;
 
        cfq_mark_cfqq_must_dispatch(cfqq);
        cfq_mark_cfqq_wait_request(cfqq);
 
-       sl = min(cfqq->slice_end - 1, (unsigned long) cfqd->cfq_slice_idle);
-
        /*
         * we don't want to idle for seeks, but we do want to allow
         * fair distribution of slice time for a process doing back-to-back
         * seeks. so allow a little bit of time for him to submit a new rq
         */
+       sl = cfqd->cfq_slice_idle;
        if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
                sl = min(sl, msecs_to_jiffies(2));
 
        mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
-       return 1;
 }
 
 static void cfq_dispatch_insert(request_queue_t *q, struct request *rq)
@@ -870,7 +1027,7 @@ static void cfq_dispatch_insert(request_queue_t *q, struct 
request *rq)
        struct cfq_queue *cfqq = RQ_CFQQ(rq);
 
        cfq_remove_request(rq);
-       cfqq->on_dispatch[rq_is_sync(rq)]++;
+       cfqq->dispatched++;
        elv_dispatch_sort(q, rq);
 }
 
@@ -891,13 +1048,13 @@ static inline struct request *cfq_check_fifo(struct 
cfq_queue *cfqq)
        if (list_empty(&cfqq->fifo))
                return NULL;
 
-       fifo = cfq_cfqq_class_sync(cfqq);
+       fifo = cfq_cfqq_sync(cfqq);
        rq = rq_entry_fifo(cfqq->fifo.next);
 
-       if (time_after(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo]))
-               return rq;
+       if (time_before(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo]))
+               return NULL;
 
-       return NULL;
+       return rq;
 }
 
 static inline int
@@ -922,23 +1079,26 @@ static struct cfq_queue *cfq_select_queue(struct 
cfq_data *cfqd)
                goto new_queue;
 
        /*
-        * slice has expired
+        * The active queue has run out of time, expire it and select new.
         */
-       if (!cfq_cfqq_must_dispatch(cfqq) && cfq_slice_used(cfqq))
+       if (cfq_slice_used(cfqq))
                goto expire;
 
        /*
-        * if queue has requests, dispatch one. if not, check if
-        * enough slice is left to wait for one
+        * The active queue has requests and isn't expired, allow it to
+        * dispatch.
         */
        if (!RB_EMPTY_ROOT(&cfqq->sort_list))
                goto keep_queue;
-       else if (cfq_cfqq_slice_new(cfqq) || cfq_cfqq_dispatched(cfqq)) {
+
+       /*
+        * No requests pending. If the active queue still has requests in
+        * flight or is idling for a new request, allow either of these
+        * conditions to happen (or time out) before selecting a new queue.
+        */
+       if (cfqq->dispatched || timer_pending(&cfqd->idle_slice_timer)) {
                cfqq = NULL;
                goto keep_queue;
-       } else if (cfq_cfqq_class_sync(cfqq)) {
-               if (cfq_arm_slice_timer(cfqd))
-                       return NULL;
        }
 
 expire:
@@ -1039,7 +1199,7 @@ static int
 cfq_dispatch_requests(request_queue_t *q, int force)
 {
        struct cfq_data *cfqd = q->elevator->elevator_data;
-       struct cfq_queue *cfqq, *prev_cfqq;
+       struct cfq_queue *cfqq;
        int dispatched;
 
        if (!cfqd->busy_queues)
@@ -1049,23 +1209,19 @@ cfq_dispatch_requests(request_queue_t *q, int force)
                return cfq_forced_dispatch(cfqd);
 
        dispatched = 0;
-       prev_cfqq = NULL;
        while ((cfqq = cfq_select_queue(cfqd)) != NULL) {
                int max_dispatch;
 
                if (cfqd->busy_queues > 1) {
                        /*
-                        * Don't repeat dispatch from the previous queue.
-                        */
-                       if (prev_cfqq == cfqq)
-                               break;
-
-                       /*
                         * So we have dispatched before in this round, if the
                         * next queue has idling enabled (must be sync), don't
-                        * allow it service until the previous have continued.
+                        * allow it service until the previous have completed.
                         */
-                       if (cfqd->rq_in_driver && cfq_cfqq_idle_window(cfqq))
+                       if (cfqd->rq_in_driver && cfq_cfqq_idle_window(cfqq) &&
+                           dispatched)
+                               break;
+                       if (cfqq->dispatched >= cfqd->cfq_quantum)
                                break;
                }
 
@@ -1078,7 +1234,6 @@ cfq_dispatch_requests(request_queue_t *q, int force)
                        max_dispatch = 1;
 
                dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
-               prev_cfqq = cfqq;
        }
 
        return dispatched;
@@ -1520,7 +1675,8 @@ cfq_update_io_thinktime(struct cfq_data *cfqd, struct 
cfq_io_context *cic)
 }
 
 static void
-cfq_update_io_seektime(struct cfq_io_context *cic, struct request *rq)
+cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic,
+                      struct request *rq)
 {
        sector_t sdist;
        u64 total;
@@ -1530,6 +1686,11 @@ cfq_update_io_seektime(struct cfq_io_context *cic, 
struct request *rq)
        else
                sdist = cic->last_request_pos - rq->sector;
 
+       if (!cic->seek_samples) {
+               cfqd->new_seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
+               cfqd->new_seek_mean = cfqd->new_seek_total / 256;
+       }
+
        /*
         * Don't allow the seek distance to get too large from the
         * odd fragment, pagein, etc
@@ -1580,13 +1741,16 @@ static int
 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
                   struct request *rq)
 {
-       struct cfq_queue *cfqq = cfqd->active_queue;
-       sector_t dist;
+       struct cfq_queue *cfqq;
 
-       if (cfq_class_idle(new_cfqq))
+       cfqq = cfqd->active_queue;
+       if (!cfqq)
                return 0;
 
-       if (!cfqq)
+       if (cfq_slice_used(cfqq))
+               return 1;
+
+       if (cfq_class_idle(new_cfqq))
                return 0;
 
        if (cfq_class_idle(cfqq))
@@ -1613,12 +1777,7 @@ cfq_should_preempt(struct cfq_data *cfqd, struct 
cfq_queue *new_cfqq,
         * if this request is as-good as one we would expect from the
         * current cfqq, let it preempt
         */
-       if (rq->sector > cfqd->last_sector)
-               dist = rq->sector - cfqd->last_sector;
-       else
-               dist = cfqd->last_sector - rq->sector;
-
-       if (dist <= cfqd->active_cic->seek_mean)
+       if (cfq_rq_close(cfqd, rq))
                return 1;
 
        return 0;
@@ -1656,28 +1815,12 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue 
*cfqq,
        if (rq_is_meta(rq))
                cfqq->meta_pending++;
 
-       /*
-        * we never wait for an async request and we don't allow preemption
-        * of an async request. so just return early
-        */
-       if (!rq_is_sync(rq)) {
-               /*
-                * sync process issued an async request, if it's waiting
-                * then expire it and kick rq handling.
-                */
-               if (cic == cfqd->active_cic &&
-                   del_timer(&cfqd->idle_slice_timer)) {
-                       cfq_slice_expired(cfqd, 0, 0);
-                       blk_start_queueing(cfqd->queue);
-               }
-               return;
-       }
-
        cfq_update_io_thinktime(cfqd, cic);
-       cfq_update_io_seektime(cic, rq);
+       cfq_update_io_seektime(cfqd, cic, rq);
        cfq_update_idle_window(cfqd, cfqq, cic);
 
        cic->last_request_pos = rq->sector + rq->nr_sectors;
+       cfqq->last_request_pos = cic->last_request_pos;
 
        if (cfqq == cfqd->active_queue) {
                /*
@@ -1726,13 +1869,11 @@ static void cfq_completed_request(request_queue_t *q, 
struct request *rq)
        now = jiffies;
 
        WARN_ON(!cfqd->rq_in_driver);
-       WARN_ON(!cfqq->on_dispatch[sync]);
+       WARN_ON(!cfqq->dispatched);
        cfqd->rq_in_driver--;
-       cfqq->on_dispatch[sync]--;
+       cfqq->dispatched--;
        cfqq->service_last = now;
 
-       cfqd->last_sector = rq->hard_sector + rq->hard_nr_sectors;
-
        if (!cfq_class_idle(cfqq))
                cfqd->last_end_request = now;
 
@@ -1752,11 +1893,12 @@ static void cfq_completed_request(request_queue_t *q, 
struct request *rq)
                }
                if (cfq_slice_used(cfqq))
                        cfq_slice_expired(cfqd, 0, 1);
-               else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list)) {
-                       if (!cfq_arm_slice_timer(cfqd))
-                               cfq_schedule_dispatch(cfqd);
-               }
+               else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list))
+                       cfq_arm_slice_timer(cfqd);
        }
+
+       if (!cfqd->rq_in_driver)
+               cfq_schedule_dispatch(cfqd);
 }
 
 /*
@@ -2101,7 +2243,6 @@ fail:
 /*
  * sysfs parts below -->
  */
-
 static ssize_t
 cfq_var_show(unsigned int var, char *page)
 {
-
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