lowlatency patch testing results (< 2ms latency :-)

Hi Andrew,

Thanks a lot for the latest iteration of the lowlatency patch.  I've done
a little testing with the rtc-debug and amlat and have triggered your
automatic stack tracing 'feature' a few times.  The actual rtc histogram
is at the very end.

For the record, all latencies are under 2ms, but on another system I think
I'm seeing a rare 7 or 8 ms bump.  I'll follow up on that.

My system is UP 700mhz athlon, SCSI system (aic7xxx), 256mb ram,  running
2.4.7 with lowlatency and rtc-debug.  To generate the load, I run amlat
with the 0% cpu consumption (default) and a disk I/O test that simulates a
hard disk recorder I/O load. (read and write to N files sequentially).

It seems like all of the traces are about the same, and come from two
places, kapmd and bdflush.

Here it is:

`bdflush'[7] is being piggy.  need_resched=1, orq=1

c1471d48 d48ba5e0 c1470232 00000007 00000001 00000001 20000001 00000008
       c0107f49 00000008 00000000 c1471dac c1471dac 00000008 c0264b00 cf556dc0
       c01080b8 00000008 c1471dac cf556dc0 c14baa00 cff07198 c14bab04 cff07140
Call Trace: [<c0107f49>] [<c01080b8>] [<c0106d54>] [<c0189ba3>] [<c016268b>] [<c01892e8>] [<c0189514>]
       [<c0189772>] [<c0173a2e>] [<c019f374>] [<c0184032>] [<c0183e1a>] [<c0183e86>] [<c011816e>] [<c0118037>]
       [<c0117d5b>] [<c01080ec>] [<c0106d54>] [<c0189ba3>] [<c01736fe>] [<c0118229>] [<c01344a1>] [<c0105000>]
       [<c0105000>] [<c0105516>] [<c0134400>]

Trace; c0107f49 <handle_IRQ_event+39/60>
Trace; c01080b8 <do_IRQ+68/b0>
Trace; c0106d54 <ret_from_intr+0/7>
Trace; c0189ba3 <scsi_request_fn+203/300>
Trace; c016268b <add_timer_randomness+cb/e0>
Trace; c01892e8 <scsi_queue_next_request+38/110>
Trace; c0189514 <__scsi_end_request+154/160>
Trace; c0189772 <scsi_io_completion+182/360>
Trace; c0173a2e <attempt_merge+5e/170>
Trace; c019f374 <rw_intr+154/160>
Trace; c0184032 <scsi_finish_command+92/a0>
Trace; c0183e1a <scsi_done+7a/80>
Trace; c0183e86 <scsi_bottom_half_handler+66/100>
Trace; c011816e <bh_action+1e/40>
Trace; c0118037 <tasklet_hi_action+87/e0>
Trace; c0117d5b <do_softirq+4b/90>
Trace; c01080ec <do_IRQ+9c/b0>
Trace; c0106d54 <ret_from_intr+0/7>
Trace; c0189ba3 <scsi_request_fn+203/300>
Trace; c01736fe <generic_unplug_device+1e/30>
Trace; c0118229 <__run_task_queue+49/60>
Trace; c01344a1 <bdflush+a1/c0>
Trace; c0105000 <_stext+0/0>
Trace; c0105000 <_stext+0/0>
Trace; c0105516 <kernel_thread+26/30>
Trace; c0134400 <bdflush+0/c0>