blkio: Implementation of IOPS limit logic

o core logic of implementing IOPS throttling.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 127 insertions, 37 deletions

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 4b492011e0de..af53f37c1b13 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -59,8 +59,13 @@ struct throtl_grp {
         /* bytes per second rate limits */
         uint64_t bps[2];
 
+        /* IOPS limits */
+        unsigned int iops[2];
+
         /* Number of bytes disptached in current slice */
         uint64_t bytes_disp[2];
+        /* Number of bio's dispatched in current slice */
+        unsigned int io_disp[2];
 
         /* When did we start a new slice */
         unsigned long slice_start[2];
@@ -194,6 +199,8 @@ static struct throtl_grp * throtl_find_alloc_tg(struct throtl_data *td,
 
         tg->bps[READ] = blkcg_get_read_bps(blkcg, tg->blkg.dev);
         tg->bps[WRITE] = blkcg_get_write_bps(blkcg, tg->blkg.dev);
+        tg->iops[READ] = blkcg_get_read_iops(blkcg, tg->blkg.dev);
+        tg->iops[WRITE] = blkcg_get_write_iops(blkcg, tg->blkg.dev);
 
         hlist_add_head(&tg->tg_node, &td->tg_list);
         td->nr_undestroyed_grps++;
@@ -335,6 +342,7 @@ static inline void
 throtl_start_new_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
 {
         tg->bytes_disp[rw] = 0;
+        tg->io_disp[rw] = 0;
         tg->slice_start[rw] = jiffies;
         tg->slice_end[rw] = jiffies + throtl_slice;
         throtl_log_tg(td, tg, "[%c] new slice start=%lu end=%lu jiffies=%lu",
@@ -365,7 +373,7 @@ throtl_slice_used(struct throtl_data *td, struct throtl_grp *tg, bool rw)
 static inline void
 throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
 {
-        unsigned long nr_slices, bytes_trim, time_elapsed;
+        unsigned long nr_slices, bytes_trim, time_elapsed, io_trim;
 
         BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
 
@@ -385,8 +393,9 @@ throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
                 return;
 
         bytes_trim = (tg->bps[rw] * throtl_slice * nr_slices)/HZ;
+        io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ;
 
-        if (!bytes_trim)
+        if (!bytes_trim && !io_trim)
                 return;
 
         if (tg->bytes_disp[rw] >= bytes_trim)
@@ -394,51 +403,62 @@ throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
         else
                 tg->bytes_disp[rw] = 0;
 
+        if (tg->io_disp[rw] >= io_trim)
+                tg->io_disp[rw] -= io_trim;
+        else
+                tg->io_disp[rw] = 0;
+
         tg->slice_start[rw] += nr_slices * throtl_slice;
 
-        throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%lu"
+        throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%lu io=%lu"
                         " start=%lu end=%lu jiffies=%lu",
-                        rw == READ ? 'R' : 'W', nr_slices, bytes_trim,
+                        rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
                         tg->slice_start[rw], tg->slice_end[rw], jiffies);
 }
 
-/*
- * Returns whether one can dispatch a bio or not. Also returns approx number
- * of jiffies to wait before this bio is with-in IO rate and can be dispatched
- */
-static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg,
-                                struct bio *bio, unsigned long *wait)
+static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg,
+                struct bio *bio, unsigned long *wait)
 {
         bool rw = bio_data_dir(bio);
-        u64 bytes_allowed, extra_bytes;
+        unsigned int io_allowed;
         unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
 
-        /*
-         * Currently whole state machine of group depends on first bio
-         * queued in the group bio list. So one should not be calling
-         * this function with a different bio if there are other bios
-         * queued.
-         */
-        BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw]));
+        jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
 
-        /* If tg->bps = -1, then BW is unlimited */
-        if (tg->bps[rw] == -1) {
+        /* Slice has just started. Consider one slice interval */
+        if (!jiffy_elapsed)
+                jiffy_elapsed_rnd = throtl_slice;
+
+        jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
+
+        io_allowed = (tg->iops[rw] * jiffies_to_msecs(jiffy_elapsed_rnd))
+                                / MSEC_PER_SEC;
+
+        if (tg->io_disp[rw] + 1 <= io_allowed) {
                 if (wait)
                         *wait = 0;
                 return 1;
         }
 
-        /*
-         * If previous slice expired, start a new one otherwise renew/extend
-         * existing slice to make sure it is at least throtl_slice interval
-         * long since now.
-         */
-        if (throtl_slice_used(td, tg, rw))
-                throtl_start_new_slice(td, tg, rw);
-        else {
-                if (time_before(tg->slice_end[rw], jiffies + throtl_slice))
-                        throtl_extend_slice(td, tg, rw, jiffies + throtl_slice);
-        }
+        /* Calc approx time to dispatch */
+        jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1;
+
+        if (jiffy_wait > jiffy_elapsed)
+                jiffy_wait = jiffy_wait - jiffy_elapsed;
+        else
+                jiffy_wait = 1;
+
+        if (wait)
+                *wait = jiffy_wait;
+        return 0;
+}
+
+static bool tg_with_in_bps_limit(struct throtl_data *td, struct throtl_grp *tg,
+                struct bio *bio, unsigned long *wait)
+{
+        bool rw = bio_data_dir(bio);
+        u64 bytes_allowed, extra_bytes;
+        unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
 
         jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
 
@@ -469,12 +489,62 @@ static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg,
          * up we did. Add that time also.
          */
         jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
-
         if (wait)
                 *wait = jiffy_wait;
+        return 0;
+}
+
+/*
+ * Returns whether one can dispatch a bio or not. Also returns approx number
+ * of jiffies to wait before this bio is with-in IO rate and can be dispatched
+ */
+static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg,
+                                struct bio *bio, unsigned long *wait)
+{
+        bool rw = bio_data_dir(bio);
+        unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
+
+        /*
+         * Currently whole state machine of group depends on first bio
+         * queued in the group bio list. So one should not be calling
+         * this function with a different bio if there are other bios
+         * queued.
+         */
+        BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw]));
 
-        if (time_before(tg->slice_end[rw], jiffies + jiffy_wait))
-                throtl_extend_slice(td, tg, rw, jiffies + jiffy_wait);
+        /* If tg->bps = -1, then BW is unlimited */
+        if (tg->bps[rw] == -1 && tg->iops[rw] == -1) {
+                if (wait)
+                        *wait = 0;
+                return 1;
+        }
+
+        /*
+         * If previous slice expired, start a new one otherwise renew/extend
+         * existing slice to make sure it is at least throtl_slice interval
+         * long since now.
+         */
+        if (throtl_slice_used(td, tg, rw))
+                throtl_start_new_slice(td, tg, rw);
+        else {
+                if (time_before(tg->slice_end[rw], jiffies + throtl_slice))
+                        throtl_extend_slice(td, tg, rw, jiffies + throtl_slice);
+        }
+
+        if (tg_with_in_bps_limit(td, tg, bio, &bps_wait)
+            && tg_with_in_iops_limit(td, tg, bio, &iops_wait)) {
+                if (wait)
+                        *wait = 0;
+                return 1;
+        }
+
+        max_wait = max(bps_wait, iops_wait);
+
+        if (wait)
+                *wait = max_wait;
+
+        if (time_before(tg->slice_end[rw], jiffies + max_wait))
+                throtl_extend_slice(td, tg, rw, jiffies + max_wait);
 
         return 0;
 }
@@ -486,13 +556,13 @@ static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
 
         /* Charge the bio to the group */
         tg->bytes_disp[rw] += bio->bi_size;
+        tg->io_disp[rw]++;
 
         /*
          * TODO: This will take blkg->stats_lock. Figure out a way
          * to avoid this cost.
          */
         blkiocg_update_dispatch_stats(&tg->blkg, bio->bi_size, rw, sync);
-
 }
 
 static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg,
@@ -763,6 +833,18 @@ static void throtl_update_blkio_group_write_bps (struct blkio_group *blkg,
         tg_of_blkg(blkg)->bps[WRITE] = write_bps;
 }
 
+static void throtl_update_blkio_group_read_iops (struct blkio_group *blkg,
+                        unsigned int read_iops)
+{
+        tg_of_blkg(blkg)->iops[READ] = read_iops;
+}
+
+static void throtl_update_blkio_group_write_iops (struct blkio_group *blkg,
+                        unsigned int write_iops)
+{
+        tg_of_blkg(blkg)->iops[WRITE] = write_iops;
+}
+
 void throtl_shutdown_timer_wq(struct request_queue *q)
 {
         struct throtl_data *td = q->td;
@@ -777,7 +859,12 @@ static struct blkio_policy_type blkio_policy_throtl = {
                                         throtl_update_blkio_group_read_bps,
                 .blkio_update_group_write_bps_fn =
                                         throtl_update_blkio_group_write_bps,
+                .blkio_update_group_read_iops_fn =
+                                        throtl_update_blkio_group_read_iops,
+                .blkio_update_group_write_iops_fn =
+                                        throtl_update_blkio_group_write_iops,
         },
+        .plid = BLKIO_POLICY_THROTL,
 };
 
 int blk_throtl_bio(struct request_queue *q, struct bio **biop)
@@ -811,9 +898,11 @@ int blk_throtl_bio(struct request_queue *q, struct bio **biop)
         }
 
 queue_bio:
-        throtl_log_tg(td, tg, "[%c] bio. disp=%u sz=%u bps=%llu"
-                        " queued=%d/%d", rw == READ ? 'R' : 'W',
+        throtl_log_tg(td, tg, "[%c] bio. bdisp=%u sz=%u bps=%llu"
+                        " iodisp=%u iops=%u queued=%d/%d",
+                        rw == READ ? 'R' : 'W',
                         tg->bytes_disp[rw], bio->bi_size, tg->bps[rw],
+                        tg->io_disp[rw], tg->iops[rw],
                         tg->nr_queued[READ], tg->nr_queued[WRITE]);
 
         throtl_add_bio_tg(q->td, tg, bio);
@@ -850,6 +939,7 @@ int blk_throtl_init(struct request_queue *q)
 
         /* Practically unlimited BW */
         tg->bps[0] = tg->bps[1] = -1;
+        tg->iops[0] = tg->iops[1] = -1;
         atomic_set(&tg->ref, 1);
 
         INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work);