[PATCH V6 09/18] blk-throttle: choose a small throtl_slice for SSD

[Shaohua Li]

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@xxxxxx>
---
 block/blk-sysfs.c    |  2 ++
 block/blk-throttle.c | 18 +++++++++++++++---
 block/blk.h          |  2 ++
 3 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 0e3fb2a..7285f74 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -907,6 +907,8 @@ int blk_register_queue(struct gendisk *disk)
 
 	blk_wb_init(q);
 
+	blk_throtl_register_queue(q);
+
 	if (!q->request_fn)
 		return 0;
 
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 49cad9a..2d05c91 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;
@@ -1957,7 +1958,6 @@ 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;
@@ -1978,6 +1978,18 @@ 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;
+}
+
 ssize_t blk_throtl_sample_time_show(struct request_queue *q, char *page)
 {
 	if (!q->td)
diff --git a/block/blk.h b/block/blk.h
index e83e757..186c67d 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -293,10 +293,12 @@ extern void blk_throtl_exit(struct request_queue *q);
 extern ssize_t blk_throtl_sample_time_show(struct request_queue *q, char *page);
 extern ssize_t blk_throtl_sample_time_store(struct request_queue *q,
 	const char *page, size_t count);
+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 */
 
 #endif /* BLK_INTERNAL_H */
-- 
2.9.3