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authorJens Axboe <axboe@suse.de>2005-05-01 11:59:06 -0400
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-05-01 11:59:06 -0400
commit1181c1f923c349acaa01bca40fe600584f265132 (patch)
treec511e606275ed31c2a203d40a372fdfbfb9fa913 /drivers/block/noop-iosched.c
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>
Diffstat (limited to 'drivers/block/noop-iosched.c')
-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 888c477e02b3..b1730b62c37e 100644
--- a/drivers/block/noop-iosched.c
+++ b/drivers/block/noop-iosched.c
@@ -13,34 +13,13 @@
13static int elevator_noop_merge(request_queue_t *q, struct request **req, 13static int elevator_noop_merge(request_queue_t *q, struct request **req,
14 struct bio *bio) 14 struct bio *bio)
15{ 15{
16 struct list_head *entry = &q->queue_head;
17 struct request *__rq;
18 int ret; 16 int ret;
19 17
20 if ((ret = elv_try_last_merge(q, bio))) { 18 ret = elv_try_last_merge(q, bio);
19 if (ret != ELEVATOR_NO_MERGE)
21 *req = q->last_merge; 20 *req = q->last_merge;
22 return ret;
23 }
24 21
25 while ((entry = entry->prev) != &q->queue_head) { 22 return ret;
26 __rq = list_entry_rq(entry);
27
28 if (__rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER))
29 break;
30 else if (__rq->flags & REQ_STARTED)
31 break;
32
33 if (!blk_fs_request(__rq))
34 continue;
35
36 if ((ret = elv_try_merge(__rq, bio))) {
37 *req = __rq;
38 q->last_merge = __rq;
39 return ret;
40 }
41 }
42
43 return ELEVATOR_NO_MERGE;
44} 23}
45 24
46static void elevator_noop_merge_requests(request_queue_t *q, struct request *req, 25static void elevator_noop_merge_requests(request_queue_t *q, struct request *req,