block: add support for IO CPU affinity
This patch adds support for controlling the IO completion CPU of
either all requests on a queue, or on a per-request basis. We export
a sysfs variable (rq_affinity) which, if set, migrates completions
of requests to the CPU that originally submitted it. A bio helper
(bio_set_completion_cpu()) is also added, so that queuers can ask
for completion on that specific CPU.
In testing, this has been show to cut the system time by as much
as 20-40% on synthetic workloads where CPU affinity is desired.
This requires a little help from the architecture, so it'll only
work as designed for archs that are using the new generic smp
helper infrastructure.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index 639624b..bb791c3 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -173,15 +173,15 @@
#define rb_entry_rq(node) rb_entry((node), struct request, rb_node)
/*
- * Hack to reuse the donelist list_head as the fifo time holder while
+ * Hack to reuse the csd.list list_head as the fifo time holder while
* the request is in the io scheduler. Saves an unsigned long in rq.
*/
-#define rq_fifo_time(rq) ((unsigned long) (rq)->donelist.next)
-#define rq_set_fifo_time(rq,exp) ((rq)->donelist.next = (void *) (exp))
+#define rq_fifo_time(rq) ((unsigned long) (rq)->csd.list.next)
+#define rq_set_fifo_time(rq,exp) ((rq)->csd.list.next = (void *) (exp))
#define rq_entry_fifo(ptr) list_entry((ptr), struct request, queuelist)
#define rq_fifo_clear(rq) do { \
list_del_init(&(rq)->queuelist); \
- INIT_LIST_HEAD(&(rq)->donelist); \
+ INIT_LIST_HEAD(&(rq)->csd.list); \
} while (0)
/*