Replace list based free/busy/requeue list with FIFO + ring
Cache friendliness of the list is pretty low. This has
provably lower overhead.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/io_u_queue.h b/io_u_queue.h
new file mode 100644
index 0000000..4f6e8e6
--- /dev/null
+++ b/io_u_queue.h
@@ -0,0 +1,75 @@
+#ifndef FIO_IO_U_QUEUE
+#define FIO_IO_U_QUEUE
+
+#include <assert.h>
+
+struct io_u;
+
+struct io_u_queue {
+ struct io_u **io_us;
+ unsigned int nr;
+};
+
+static inline struct io_u *io_u_qpop(struct io_u_queue *q)
+{
+ if (q->nr)
+ return q->io_us[--q->nr];
+
+ return NULL;
+}
+
+static inline void io_u_qpush(struct io_u_queue *q, struct io_u *io_u)
+{
+ q->io_us[q->nr++] = io_u;
+}
+
+static inline int io_u_qempty(struct io_u_queue *q)
+{
+ return !q->nr;
+}
+
+#define io_u_qiter(q, io_u, i) \
+ for (i = 0, io_u = (q)->io_us[0]; i < (q)->nr; i++, io_u = (q)->io_us[i])
+
+int io_u_qinit(struct io_u_queue *q, unsigned int nr);
+void io_u_qexit(struct io_u_queue *q);
+
+struct io_u_ring {
+ unsigned int head;
+ unsigned int tail;
+ unsigned int max;
+ struct io_u **ring;
+};
+
+int io_u_rinit(struct io_u_ring *ring, unsigned int nr);
+void io_u_rexit(struct io_u_ring *ring);
+
+static inline void io_u_rpush(struct io_u_ring *r, struct io_u *io_u)
+{
+ if (r->head + 1 != r->tail) {
+ r->ring[r->head] = io_u;
+ r->head = (r->head + 1) & (r->max - 1);
+ return;
+ }
+
+ assert(0);
+}
+
+static inline struct io_u *io_u_rpop(struct io_u_ring *r)
+{
+ if (r->head != r->tail) {
+ struct io_u *io_u = r->ring[r->tail];
+
+ r->tail = (r->tail + 1) & (r->max - 1);
+ return io_u;
+ }
+
+ return NULL;
+}
+
+static inline int io_u_rempty(struct io_u_ring *ring)
+{
+ return ring->head == ring->tail;
+}
+
+#endif