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>

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 6300f3ed70d2c1134b4fa94f7b9b235cc04fcae2..f03e158ee1977544f89476ee5634ba0a46bc582b 100644 (file)
--- 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();
 }