lots of unplugged by timer normal or abnormal?

[Simon Kirby <sim@hostway.ca>]

Hello,

I was just testing out blktrace/blkparse/btrace on a box that is hitting
some performance walls, and noticed that there are a fair amonut of "UT"
events (unplug by timer).  Is this normal/expected?  For example:

[sroot@nas04:/root]# btrace /dev/etherd/e7.0 | grep T
152,32   4     1379     3.582513494     0 UT   N [swapper] 8
152,32   1     1289     4.329760067     0 UT   N [swapper] 1
152,32   3     1132     4.362257911     0 UT   N [swapper] 3
152,32   7     1070     4.375258374     0 UT   N [swapper] 1
152,32   3     1146     4.382260172     0 UT   N [swapper] 5
152,32   1     1318     4.417759727  2830 UT   N [nfsd] 3
152,32   5     1003     4.498757105     0 UT   N [swapper] 1
152,32   1     1368     4.517761127     0 UT   N [swapper] 1
152,32   0     1133     4.585522116     0 UT   N [swapper] 5

This is on 2.6.30.5 with the 2.6.30.6 XFS patches.

Cheers,

Simon-