On Tue, Oct 06, 2009 at 04:20:32PM -0400, Alan D. Brunelle wrote:
> Coincidentally I was investigating something similar w/ RHEL 5.4 at this
> very moment - just wanted to know if that was a common denominator.
>
> Could you run the attached SystemTap script and send out the output?
> [You may have to get `systemtap' though...]
Thanks for the excuse to try SystemTap. :) I have some traces, but I
don't think the UT case is abnormal. On my desktop at home, I can see
btraces such as this, which seem to show it happening often:
# btrace /dev/md0
9,0 2 1 0.000000000 11679 P N [flush-9:0]
9,0 2 2 0.000006301 11679 Q W 103873856 + 8 [flush-9:0]
9,0 2 3 0.001946762 0 UT N [swapper] 0
9,0 2 4 0.001964494 290 U N [kblockd/2] 0
9,0 2 5 4.625939573 13087 Q W 103899840 + 8 [firefox-bin]
9,0 2 6 4.635987726 13087 P N [firefox-bin]
9,0 2 7 4.637612451 13087 UT N [firefox-bin] 0
9,0 2 8 4.637670985 290 U N [kblockd/2] 0
9,0 0 1 4.996817219 11679 Q W 85739464 + 8 [flush-9:0]
9,0 0 2 5.005772973 11679 P N [flush-9:0]
9,0 0 3 5.005789934 11679 Q W 92127240 + 8 [flush-9:0]
9,0 0 4 5.012468560 4 UT N [ksoftirqd/0] 0
9,0 0 5 5.012482690 288 U N [kblockd/0] 0
9,0 2 9 6.829559401 13087 Q W 103907504 + 8 [firefox-bin]
9,0 2 10 6.838558733 13087 P N [firefox-bin]
9,0 2 11 6.838560239 13087 Q W 103907512 + 8 [firefox-bin]
9,0 2 12 6.838561798 13087 Q W 103907528 + 8 [firefox-bin]
9,0 2 13 6.838563499 13087 Q W 103907624 + 8 [firefox-bin]
9,0 2 14 6.838564916 13087 Q W 103907664 + 8 [firefox-bin]
9,0 2 15 6.838566357 13087 Q W 103907672 + 8 [firefox-bin]
9,0 2 16 6.841928170 0 UT N [swapper] 0
9,0 2 17 6.841934150 290 U N [kblockd/2] 0
^CCPU0 (9,0):
Reads Queued: 0, 0KiB Writes Queued: 2, 8KiB
Read Dispatches: 0, 0KiB Write Dispatches: 0, 0KiB
Reads Requeued: 0 Writes Requeued: 0
Reads Completed: 0, 0KiB Writes Completed: 0, 0KiB
Read Merges: 0, 0KiB Write Merges: 0, 0KiB
Read depth: 0 Write depth: 0
IO unplugs: 1 Timer unplugs: 1
CPU2 (9,0):
Reads Queued: 0, 0KiB Writes Queued: 8, 32KiB
Read Dispatches: 0, 0KiB Write Dispatches: 0, 0KiB
Reads Requeued: 0 Writes Requeued: 0
Reads Completed: 0, 0KiB Writes Completed: 0, 0KiB
Read Merges: 0, 0KiB Write Merges: 0, 0KiB
Read depth: 0 Write depth: 0
IO unplugs: 3 Timer unplugs: 3
Total (9,0):
Reads Queued: 0, 0KiB Writes Queued: 10, 40KiB
Read Dispatches: 0, 0KiB Write Dispatches: 0, 0KiB
Reads Requeued: 0 Writes Requeued: 0
Reads Completed: 0, 0KiB Writes Completed: 0, 0KiB
Read Merges: 0, 0KiB Write Merges: 0, 0KiB
IO unplugs: 4 Timer unplugs: 4
Throughput (R/W): 0KiB/s / 0KiB/s
Events (9,0): 22 entries
Skips: 0 forward (0 - 0.0%)
This is on ext3 via MD raid 1, 0eca52a92735f43462165efe00a7e394345fb38e
kernel version aka "2.6.32rc3".
Simon-
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