[PATCH V5 03/13] sbitmap: add helpers for updating allocation hint

Ming Lei
2020-11-19T09:34:38Z

Add helpers for updating allocation hint, so that we can
avoid to duplicate code.

Prepare for moving allocation hint into sbitmap.

Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Tested-by: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
lib/sbitmap.c | 93 ++++++++++++++++++++++++++++++---------------------
1 file changed, 54 insertions(+), 39 deletions(-)

diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index 8d920d66d42a..4e4423414f4d 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -9,6 +9,55 @@
#include <linux/sbitmap.h>
#include <linux/seq_file.h>

+static int init_alloc_hint(struct sbitmap_queue *sbq, gfp_t flags)
+{
+ unsigned depth = sbq->sb.depth;
+
+ sbq->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
+ if (!sbq->alloc_hint)
+ return -ENOMEM;
+
+ if (depth && !sbq->sb.round_robin) {
+ int i;
+
+ for_each_possible_cpu(i)
+ *per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth;
+ }
+
+ return 0;
+}
+
+static inline unsigned update_alloc_hint_before_get(struct sbitmap_queue *sbq,
+ unsigned int depth)
+{
+ unsigned hint;
+
+ hint = this_cpu_read(*sbq->alloc_hint);
+ if (unlikely(hint >= depth)) {
+ hint = depth ? prandom_u32() % depth : 0;
+ this_cpu_write(*sbq->alloc_hint, hint);
+ }
+
+ return hint;
+}
+
+static inline void update_alloc_hint_after_get(struct sbitmap_queue *sbq,
+ unsigned int depth,
+ unsigned int hint,
+ unsigned int nr)
+{
+ if (nr == -1) {
+ /* If the map is full, a hint won't do us much good. */
+ this_cpu_write(*sbq->alloc_hint, 0);
+ } else if (nr == hint || unlikely(sbq->sb.round_robin)) {
+ /* Only update the hint if we used it. */
+ hint = nr + 1;
+ if (hint >= depth - 1)
+ hint = 0;
+ this_cpu_write(*sbq->alloc_hint, hint);
+ }
+}
+
/*
* See if we have deferred clears that we can batch move
*/
@@ -363,17 +412,11 @@ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
if (ret)
return ret;

- sbq->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
- if (!sbq->alloc_hint) {
+ if (init_alloc_hint(sbq, flags) != 0) {
sbitmap_free(&sbq->sb);
return -ENOMEM;
}

- if (depth && !round_robin) {
- for_each_possible_cpu(i)
- *per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth;
- }
-
sbq->min_shallow_depth = UINT_MAX;
sbq->wake_batch = sbq_calc_wake_batch(sbq, depth);
atomic_set(&sbq->wake_index, 0);
@@ -426,24 +469,10 @@ int __sbitmap_queue_get(struct sbitmap_queue *sbq)
unsigned int hint, depth;
int nr;

- hint = this_cpu_read(*sbq->alloc_hint);
depth = READ_ONCE(sbq->sb.depth);
- if (unlikely(hint >= depth)) {
- hint = depth ? prandom_u32() % depth : 0;
- this_cpu_write(*sbq->alloc_hint, hint);
- }
+ hint = update_alloc_hint_before_get(sbq, depth);
nr = sbitmap_get(&sbq->sb, hint);
-
- if (nr == -1) {
- /* If the map is full, a hint won't do us much good. */
- this_cpu_write(*sbq->alloc_hint, 0);
- } else if (nr == hint || unlikely(sbq->sb.round_robin)) {
- /* Only update the hint if we used it. */
- hint = nr + 1;
- if (hint >= depth - 1)
- hint = 0;
- this_cpu_write(*sbq->alloc_hint, hint);
- }
+ update_alloc_hint_after_get(sbq, depth, hint, nr);

return nr;
}
@@ -457,24 +486,10 @@ int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,

WARN_ON_ONCE(shallow_depth < sbq->min_shallow_depth);

- hint = this_cpu_read(*sbq->alloc_hint);
depth = READ_ONCE(sbq->sb.depth);
- if (unlikely(hint >= depth)) {
- hint = depth ? prandom_u32() % depth : 0;
- this_cpu_write(*sbq->alloc_hint, hint);
- }
+ hint = update_alloc_hint_before_get(sbq, depth);
nr = sbitmap_get_shallow(&sbq->sb, hint, shallow_depth);
-
- if (nr == -1) {
- /* If the map is full, a hint won't do us much good. */
- this_cpu_write(*sbq->alloc_hint, 0);
- } else if (nr == hint || unlikely(sbq->sb.round_robin)) {
- /* Only update the hint if we used it. */
- hint = nr + 1;
- if (hint >= depth - 1)
- hint = 0;
- this_cpu_write(*sbq->alloc_hint, hint);
- }
+ update_alloc_hint_after_get(sbq, depth, hint, nr);

return nr;
}
--
2.25.4