cfq-iosched: split seeky coop queues after one slice

Currently we split seeky coop queues after 1s, which is too big. Below patch
marks seeky coop queue split_coop flag after one slice. After that, if new
requests come in, the queues will be splitted. Patch is suggested by Corrado.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Reviewed-by: Corrado Zoccolo <czoccolo@gmail.com>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 17b768d..023f4e6 100644 (file)
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -42,16 +42,13 @@ static const int cfq_hist_divisor = 4;
  */
 #define CFQ_MIN_TT             (2)
 
-/*
- * Allow merged cfqqs to perform this amount of seeky I/O before
- * deciding to break the queues up again.
- */
-#define CFQQ_COOP_TOUT         (HZ)
-
 #define CFQ_SLICE_SCALE                (5)
 #define CFQ_HW_QUEUE_MIN       (5)
 #define CFQ_SERVICE_SHIFT       12
 
+#define CFQQ_SEEK_THR          8 * 1024
+#define CFQQ_SEEKY(cfqq)       ((cfqq)->seek_mean > CFQQ_SEEK_THR)
+
 #define RQ_CIC(rq)             \
        ((struct cfq_io_context *) (rq)->elevator_private)
 #define RQ_CFQQ(rq)            (struct cfq_queue *) ((rq)->elevator_private2)
@@ -137,7 +134,6 @@ struct cfq_queue {
        u64 seek_total;
        sector_t seek_mean;
        sector_t last_request_pos;
-       unsigned long seeky_start;
 
        pid_t pid;
 
@@ -314,6 +310,7 @@ enum cfqq_state_flags {
        CFQ_CFQQ_FLAG_slice_new,        /* no requests dispatched in slice */
        CFQ_CFQQ_FLAG_sync,             /* synchronous queue */
        CFQ_CFQQ_FLAG_coop,             /* cfqq is shared */
+       CFQ_CFQQ_FLAG_split_coop,       /* shared cfqq will be splitted */
        CFQ_CFQQ_FLAG_deep,             /* sync cfqq experienced large depth */
        CFQ_CFQQ_FLAG_wait_busy,        /* Waiting for next request */
 };
@@ -342,6 +339,7 @@ CFQ_CFQQ_FNS(prio_changed);
 CFQ_CFQQ_FNS(slice_new);
 CFQ_CFQQ_FNS(sync);
 CFQ_CFQQ_FNS(coop);
+CFQ_CFQQ_FNS(split_coop);
 CFQ_CFQQ_FNS(deep);
 CFQ_CFQQ_FNS(wait_busy);
 #undef CFQ_CFQQ_FNS
@@ -1566,6 +1564,15 @@ __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
        cfq_clear_cfqq_wait_busy(cfqq);
 
        /*
+        * If this cfqq is shared between multiple processes, check to
+        * make sure that those processes are still issuing I/Os within
+        * the mean seek distance.  If not, it may be time to break the
+        * queues apart again.
+        */
+       if (cfq_cfqq_coop(cfqq) && CFQQ_SEEKY(cfqq))
+               cfq_mark_cfqq_split_coop(cfqq);
+
+       /*
         * store what was left of this slice, if the queue idled/timed out
         */
        if (timed_out && !cfq_cfqq_slice_new(cfqq)) {
@@ -1663,9 +1670,6 @@ static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
                return cfqd->last_position - blk_rq_pos(rq);
 }
 
-#define CFQQ_SEEK_THR          8 * 1024
-#define CFQQ_SEEKY(cfqq)       ((cfqq)->seek_mean > CFQQ_SEEK_THR)
-
 static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                               struct request *rq, bool for_preempt)
 {
@@ -3000,19 +3004,6 @@ cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
        total = cfqq->seek_total + (cfqq->seek_samples/2);
        do_div(total, cfqq->seek_samples);
        cfqq->seek_mean = (sector_t)total;
-
-       /*
-        * If this cfqq is shared between multiple processes, check to
-        * make sure that those processes are still issuing I/Os within
-        * the mean seek distance.  If not, it may be time to break the
-        * queues apart again.
-        */
-       if (cfq_cfqq_coop(cfqq)) {
-               if (CFQQ_SEEKY(cfqq) && !cfqq->seeky_start)
-                       cfqq->seeky_start = jiffies;
-               else if (!CFQQ_SEEKY(cfqq))
-                       cfqq->seeky_start = 0;
-       }
 }
 
 /*
@@ -3453,14 +3444,6 @@ cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic,
        return cic_to_cfqq(cic, 1);
 }
 
-static int should_split_cfqq(struct cfq_queue *cfqq)
-{
-       if (cfqq->seeky_start &&
-           time_after(jiffies, cfqq->seeky_start + CFQQ_COOP_TOUT))
-               return 1;
-       return 0;
-}
-
 /*
  * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
  * was the last process referring to said cfqq.
@@ -3469,9 +3452,9 @@ static struct cfq_queue *
 split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)
 {
        if (cfqq_process_refs(cfqq) == 1) {
-               cfqq->seeky_start = 0;
                cfqq->pid = current->pid;
                cfq_clear_cfqq_coop(cfqq);
+               cfq_clear_cfqq_split_coop(cfqq);
                return cfqq;
        }
 
@@ -3510,7 +3493,7 @@ new_queue:
                /*
                 * If the queue was seeky for too long, break it apart.
                 */
-               if (cfq_cfqq_coop(cfqq) && should_split_cfqq(cfqq)) {
+               if (cfq_cfqq_coop(cfqq) && cfq_cfqq_split_coop(cfqq)) {
                        cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
                        cfqq = split_cfqq(cic, cfqq);
                        if (!cfqq)