cfq-iosched: blktrace print per slice sector stats

o Divyesh had gotten rid of this code in the past. I want to re-introduce it
  back as it helps me a lot during debugging.

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Reviewed-by: Divyesh Shah <dpshah@google.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 85e48192754d..f65c6f01c475 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -148,6 +148,8 @@ struct cfq_queue {
         struct cfq_queue *new_cfqq;
         struct cfq_group *cfqg;
         struct cfq_group *orig_cfqg;
+        /* Number of sectors dispatched from queue in single dispatch round */
+        unsigned long nr_sectors;
 };
 
 /*
@@ -960,8 +962,9 @@ static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
 
         cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
                                         st->min_vdisktime);
-        cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u disp=%u charge=%u iops=%u",
-                        used_sl, cfqq->slice_dispatch, charge, iops_mode(cfqd));
+        cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u disp=%u charge=%u iops=%u"
+                        " sect=%u", used_sl, cfqq->slice_dispatch, charge,
+                        iops_mode(cfqd), cfqq->nr_sectors);
         cfq_blkiocg_update_timeslice_used(&cfqg->blkg, used_sl);
         cfq_blkiocg_set_start_empty_time(&cfqg->blkg);
 }
@@ -1609,6 +1612,7 @@ static void __cfq_set_active_queue(struct cfq_data *cfqd,
                 cfqq->allocated_slice = 0;
                 cfqq->slice_end = 0;
                 cfqq->slice_dispatch = 0;
+                cfqq->nr_sectors = 0;
 
                 cfq_clear_cfqq_wait_request(cfqq);
                 cfq_clear_cfqq_must_dispatch(cfqq);
@@ -1971,6 +1975,7 @@ static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
         elv_dispatch_sort(q, rq);
 
         cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
+        cfqq->nr_sectors += blk_rq_sectors(rq);
         cfq_blkiocg_update_dispatch_stats(&cfqq->cfqg->blkg, blk_rq_bytes(rq),
                                         rq_data_dir(rq), rq_is_sync(rq));
 }