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authorJens Axboe <axboe@suse.de>2005-05-01 08:59:06 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-05-01 08:59:06 -0700
commit1181c1f923c349acaa01bca40fe600584f265132 (patch)
treec511e606275ed31c2a203d40a372fdfbfb9fa913
parent41f11a4fa378201e902892130b11d78cf7cf8e10 (diff)
[PATCH] noop-iosched: kill O(N) merge scan
Profiling hit rates on merging shows that the last merge hint works extremely well for most work loads. So lets kill the linear merge scan in noop-iosched, so it provides O(1) run time for any operation. Testing credits go to Ken Chen from Intel. Signed-off-by: Jens Axboe <axboe@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--drivers/block/noop-iosched.c27
1 files changed, 3 insertions, 24 deletions
diff --git a/drivers/block/noop-iosched.c b/drivers/block/noop-iosched.c
index 888c477e02b..b1730b62c37 100644
--- a/drivers/block/noop-iosched.c
+++ b/drivers/block/noop-iosched.c
@@ -13,34 +13,13 @@
static int elevator_noop_merge(request_queue_t *q, struct request **req,
struct bio *bio)
{
- struct list_head *entry = &q->queue_head;
- struct request *__rq;
int ret;
- if ((ret = elv_try_last_merge(q, bio))) {
+ ret = elv_try_last_merge(q, bio);
+ if (ret != ELEVATOR_NO_MERGE)
*req = q->last_merge;
- return ret;
- }
- while ((entry = entry->prev) != &q->queue_head) {
- __rq = list_entry_rq(entry);
-
- if (__rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER))
- break;
- else if (__rq->flags & REQ_STARTED)
- break;
-
- if (!blk_fs_request(__rq))
- continue;
-
- if ((ret = elv_try_merge(__rq, bio))) {
- *req = __rq;
- q->last_merge = __rq;
- return ret;
- }
- }
-
- return ELEVATOR_NO_MERGE;
+ return ret;
}
static void elevator_noop_merge_requests(request_queue_t *q, struct request *req,