[PATCH] Moved UNPLUG traces to match 1-to-1 with PLUG traces
From: Alan D. Brunelle
Date: Fri Feb 01 2008 - 15:11:25 EST
Currently, with DM (and probably MD) we can receive streams of multiple
PLUG and/or UNPLUG traces on the lower devices:
8,32 1 910438 25.383725302 12843 P N [mkfs.ext2]
8,32 1 911627 25.385613612 12843 P N [mkfs.ext2]
8,32 1 911819 25.385931255 12843 P N [mkfs.ext2]
8,32 1 913176 25.388396840 12843 P N [mkfs.ext2]
8,32 1 914170 25.391634524 12843 P N [mkfs.ext2]
8,32 1 915239 25.393325078 12843 P N [mkfs.ext2]
8,32 1 915473 25.397930230 0 UT N [swapper] 18
8,32 1 915474 25.397936145 32 U N [kblockd/1] 18
8,32 1 915497 25.594446953 12843 P N [mkfs.ext2]
8,32 1 916806 25.596543309 12843 P N [mkfs.ext2]
8,32 1 918351 25.599276485 12843 P N [mkfs.ext2]
8,32 1 918377 25.599313544 12843 U N [mkfs.ext2] 9
The PLUG traces are "protected" by the test-and-clear functionality
in blk_plug_device, however the UNPLUG traces has no such protection.
And in the case where MD or DM were involved, the upper level dev as
well as the lower level devs would both go through blk_unplug which
would generate extra UNPLUGS.
With the proposed change, I only see a good one-to-one mapping of PLUG
and UNPLUG traces on the underlying devices. However, we no longer see
the UNPLUG traces on the MD or DM devices, which one could argue makes
sense because (a) those devices don't have request queues managed by
the block layer, and thus (b) they never had any notion of having been
plugged. (So we saw UNPLUG traces on devices that never had PLUG traces.)
A similar stream with the new patch:
8,32 1 882908 24.179721271 7539 P N [mkfs.ext2]
8,32 1 884121 24.182232467 7539 U N [mkfs.ext2] 10
8,32 1 884129 24.182305789 7539 P N [mkfs.ext2]
8,32 1 885478 24.184748842 7539 U N [mkfs.ext2] 14
8,32 1 885487 24.184791013 7539 P N [mkfs.ext2]
8,32 1 886336 24.186479185 7539 U N [mkfs.ext2] 15
8,32 1 886343 24.186516024 7539 P N [mkfs.ext2]
8,32 1 886414 24.186637771 7539 U N [mkfs.ext2] 14
8,32 1 886420 24.186649173 7539 P N [mkfs.ext2]
8,32 1 886726 24.193329121 0 UT N [swapper] 15
8,32 1 886727 24.193336428 32 U N [kblockd/1] 15
8,32 1 886748 24.354771821 7539 P N [mkfs.ext2]
8,32 1 888081 24.357279380 7539 U N [mkfs.ext2] 4
8,32 1 888090 24.357323899 7539 P N [mkfs.ext2]
8,32 1 888934 24.358969886 7539 U N [mkfs.ext2] 5
8,32 1 888942 24.359019161 7539 P N [mkfs.ext2]
8,32 1 890147 24.361314613 7539 U N [mkfs.ext2] 8
The proposed patch was tested with a 2.6.22-based kernel, and
compile tested with a 2.6.24-based tree from 31 January 2008
(85004cc367abc000aa36c0d0e270ab609a68b0cb).
Signed-off-by: Alan D. Brunelle <alan.brunelle@xxxxxx>
---
block/blk-core.c | 12 ++++--------
1 files changed, 4 insertions(+), 8 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 8ff9944..1d148b5 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -218,6 +218,9 @@ int blk_remove_plug(struct request_queue *q)
if (!test_and_clear_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags))
return 0;
+ blk_add_trace_pdu_int(q, BLK_TA_UNPLUG_IO, NULL,
+ q->rq.count[READ] + q->rq.count[WRITE]);
+
del_timer(&q->unplug_timer);
return 1;
}
@@ -271,9 +274,6 @@ void blk_unplug_work(struct work_struct *work)
struct request_queue *q =
container_of(work, struct request_queue, unplug_work);
- blk_add_trace_pdu_int(q, BLK_TA_UNPLUG_IO, NULL,
- q->rq.count[READ] + q->rq.count[WRITE]);
-
q->unplug_fn(q);
}
@@ -292,12 +292,8 @@ void blk_unplug(struct request_queue *q)
/*
* devices don't necessarily have an ->unplug_fn defined
*/
- if (q->unplug_fn) {
- blk_add_trace_pdu_int(q, BLK_TA_UNPLUG_IO, NULL,
- q->rq.count[READ] + q->rq.count[WRITE]);
-
+ if (q->unplug_fn)
q->unplug_fn(q);
- }
}
EXPORT_SYMBOL(blk_unplug);
--
1.5.2.5
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