blk-throttle: choose a small throtl_slice for SSD

The throtl_slice is 100ms by default. This is a long time for SSD, a lot
of IO can run. To make cgroups have smoother throughput, we choose a
small value (20ms) for SSD.

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

3 files changed, 24 insertions, 3 deletions

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index b315e62cc914..7f090dd15ca6 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -906,6 +906,8 @@ int blk_register_queue(struct gendisk *disk)
 
         blk_wb_init(q);
 
+        blk_throtl_register_queue(q);
+
         if (q->request_fn || (q->mq_ops && q->elevator)) {
                 ret = elv_register_queue(q);
                 if (ret) {
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 93841da808a1..d00c1c1e99e4 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -18,8 +18,9 @@ static int throtl_grp_quantum = 8;
 /* Total max dispatch from all groups in one round */
 static int throtl_quantum = 32;
 
-/* Throttling is performed over 100ms slice and after that slice is renewed */
-#define DFL_THROTL_SLICE (HZ / 10)
+/* Throttling is performed over a slice and after that slice is renewed */
+#define DFL_THROTL_SLICE_HD (HZ / 10)
+#define DFL_THROTL_SLICE_SSD (HZ / 50)
 #define MAX_THROTL_SLICE (HZ)
 
 static struct blkcg_policy blkcg_policy_throtl;
@@ -1961,7 +1962,6 @@ int blk_throtl_init(struct request_queue *q)
 
         q->td = td;
         td->queue = q;
-        td->throtl_slice = DFL_THROTL_SLICE;
 
         td->limit_valid[LIMIT_MAX] = true;
         td->limit_index = LIMIT_MAX;
@@ -1982,6 +1982,23 @@ void blk_throtl_exit(struct request_queue *q)
         kfree(q->td);
 }
 
+void blk_throtl_register_queue(struct request_queue *q)
+{
+        struct throtl_data *td;
+
+        td = q->td;
+        BUG_ON(!td);
+
+        if (blk_queue_nonrot(q))
+                td->throtl_slice = DFL_THROTL_SLICE_SSD;
+        else
+                td->throtl_slice = DFL_THROTL_SLICE_HD;
+#ifndef CONFIG_BLK_DEV_THROTTLING_LOW
+        /* if no low limit, use previous default */
+        td->throtl_slice = DFL_THROTL_SLICE_HD;
+#endif
+}
+
 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
 ssize_t blk_throtl_sample_time_show(struct request_queue *q, char *page)
 {
diff --git a/block/blk.h b/block/blk.h
index bcd3de6c1081..13070c325858 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -319,10 +319,12 @@ static inline struct io_context *create_io_context(gfp_t gfp_mask, int node)
 extern void blk_throtl_drain(struct request_queue *q);
 extern int blk_throtl_init(struct request_queue *q);
 extern void blk_throtl_exit(struct request_queue *q);
+extern void blk_throtl_register_queue(struct request_queue *q);
 #else /* CONFIG_BLK_DEV_THROTTLING */
 static inline void blk_throtl_drain(struct request_queue *q) { }
 static inline int blk_throtl_init(struct request_queue *q) { return 0; }
 static inline void blk_throtl_exit(struct request_queue *q) { }
+static inline void blk_throtl_register_queue(struct request_queue *q) { }
 #endif /* CONFIG_BLK_DEV_THROTTLING */
 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
 extern ssize_t blk_throtl_sample_time_show(struct request_queue *q, char *page);