blk-throttle: add interface to configure idle time threshold

Add interface to configure the threshold. The io.low interface will
like:
echo "8:16 rbps=2097152 wbps=max idle=2000" > io.low

idle is in microsecond unit.

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 28 insertions, 13 deletions

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 6300f3ed70d2..f03e158ee197 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -181,6 +181,8 @@ struct throtl_data
         unsigned int limit_index;
         bool limit_valid[LIMIT_CNT];
 
+        unsigned long dft_idletime_threshold; /* us */
+
         unsigned long low_upgrade_time;
         unsigned long low_downgrade_time;
 
@@ -477,10 +479,7 @@ static void throtl_pd_init(struct blkg_policy_data *pd)
                 sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
         tg->td = td;
 
-        if (blk_queue_nonrot(td->queue))
-                tg->idletime_threshold = DFL_IDLE_THRESHOLD_SSD;
-        else
-                tg->idletime_threshold = DFL_IDLE_THRESHOLD_HD;
+        tg->idletime_threshold = td->dft_idletime_threshold;
 }
 
 /*
@@ -1449,6 +1448,7 @@ static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd,
         char bufs[4][21] = { "max", "max", "max", "max" };
         u64 bps_dft;
         unsigned int iops_dft;
+        char idle_time[26] = "";
 
         if (!dname)
                 return 0;
@@ -1464,7 +1464,9 @@ static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd,
         if (tg->bps_conf[READ][off] == bps_dft &&
             tg->bps_conf[WRITE][off] == bps_dft &&
             tg->iops_conf[READ][off] == iops_dft &&
-            tg->iops_conf[WRITE][off] == iops_dft)
+            tg->iops_conf[WRITE][off] == iops_dft &&
+            (off != LIMIT_LOW || tg->idletime_threshold ==
+                                  tg->td->dft_idletime_threshold))
                 return 0;
 
         if (tg->bps_conf[READ][off] != bps_dft)
@@ -1479,9 +1481,16 @@ static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd,
         if (tg->iops_conf[WRITE][off] != iops_dft)
                 snprintf(bufs[3], sizeof(bufs[3]), "%u",
                         tg->iops_conf[WRITE][off]);
+        if (off == LIMIT_LOW) {
+                if (tg->idletime_threshold == ULONG_MAX)
+                        strcpy(idle_time, " idle=max");
+                else
+                        snprintf(idle_time, sizeof(idle_time), " idle=%lu",
+                                tg->idletime_threshold);
+        }
 
-        seq_printf(sf, "%s rbps=%s wbps=%s riops=%s wiops=%s\n",
-                   dname, bufs[0], bufs[1], bufs[2], bufs[3]);
+        seq_printf(sf, "%s rbps=%s wbps=%s riops=%s wiops=%s%s\n",
+                   dname, bufs[0], bufs[1], bufs[2], bufs[3], idle_time);
         return 0;
 }
 
@@ -1499,6 +1508,7 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of,
         struct blkg_conf_ctx ctx;
         struct throtl_grp *tg;
         u64 v[4];
+        unsigned long idle_time;
         int ret;
         int index = of_cft(of)->private;
 
@@ -1513,6 +1523,7 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of,
         v[2] = tg->iops_conf[READ][index];
         v[3] = tg->iops_conf[WRITE][index];
 
+        idle_time = tg->idletime_threshold;
         while (true) {
                 char tok[27];   /* wiops=18446744073709551616 */
                 char *p;
@@ -1544,6 +1555,8 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of,
                         v[2] = min_t(u64, val, UINT_MAX);
                 else if (!strcmp(tok, "wiops"))
                         v[3] = min_t(u64, val, UINT_MAX);
+                else if (off == LIMIT_LOW && !strcmp(tok, "idle"))
+                        idle_time = val;
                 else
                         goto out_finish;
         }
@@ -1572,6 +1585,8 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of,
                 blk_throtl_update_limit_valid(tg->td);
                 if (tg->td->limit_valid[LIMIT_LOW])
                         tg->td->limit_index = LIMIT_LOW;
+                tg->idletime_threshold = (idle_time == ULONG_MAX) ?
+                        ULONG_MAX : idle_time;
         }
         tg_conf_updated(tg);
         ret = 0;
@@ -2122,10 +2137,13 @@ void blk_throtl_register_queue(struct request_queue *q)
         td = q->td;
         BUG_ON(!td);
 
-        if (blk_queue_nonrot(q))
+        if (blk_queue_nonrot(q)) {
                 td->throtl_slice = DFL_THROTL_SLICE_SSD;
-        else
+                td->dft_idletime_threshold = DFL_IDLE_THRESHOLD_SSD;
+        } else {
                 td->throtl_slice = DFL_THROTL_SLICE_HD;
+                td->dft_idletime_threshold = DFL_IDLE_THRESHOLD_HD;
+        }
 #ifndef CONFIG_BLK_DEV_THROTTLING_LOW
         /* if no low limit, use previous default */
         td->throtl_slice = DFL_THROTL_SLICE_HD;
@@ -2139,10 +2157,7 @@ void blk_throtl_register_queue(struct request_queue *q)
         blkg_for_each_descendant_post(blkg, pos_css, q->root_blkg) {
                 struct throtl_grp *tg = blkg_to_tg(blkg);
 
-                if (blk_queue_nonrot(q))
-                        tg->idletime_threshold = DFL_IDLE_THRESHOLD_SSD;
-                else
-                        tg->idletime_threshold = DFL_IDLE_THRESHOLD_HD;
+                tg->idletime_threshold = td->dft_idletime_threshold;
         }
         rcu_read_unlock();
 }