Date: Wed, 12 Apr 2000 14:57:44 -0400 (EDT) From: Dan Roberts - GWIS <ddr@gwis.com> To: freebsd-scsi@freebsd.org Subject: Possible CAM scheduling problem with DPT SrIV controller? Message-ID: <Pine.BSF.4.10.10004121446340.39412-100000@darcy.gwis.com>
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I've got a SmartRAID IV controller in my FreeBSD 3.4 machine.. when disk
activity becomes high, the system is unresponsive. I've spoken with the
driver's author and it's his opinion that the problem lies withing the
SCSI CAM subsystem. I can demonstrate this problem easily by making the
system work on a large file, as demonstrated below.
$ dd if=/dev/zero of=/home/ddr/bigfile bs=1k count=200000
This is a snapshot of the system under a lighter than average load, before
issuing the dd command (increments of 1 second):
tty da0 cpu
tin tout KB/t tps MB/s us ni sy in id
12 240 6.83 30 0.20 12 0 8 1 79
15 2039 7.36 11 0.08 9 0 12 1 78
18 325 7.29 57 0.41 13 0 12 3 72
18 2074 6.76 85 0.56 19 0 42 2 37
12 412 7.32 19 0.13 3 0 10 1 86
89 2234 6.75 16 0.10 8 0 13 2 78
This is the same system a few minutes later while dd is running:
tty da0 cpu
tin tout KB/t tps MB/s us ni sy in id
0 455 16.73 184 3.01 2 0 1 2 95
0 688 8.83 325 2.80 2 0 2 2 95
0 229 21.73 65 1.39 8 0 53 2 38
0 2080 64.00 30 1.86 1 0 2 2 95
0 229 14.28 212 2.95 2 0 0 3 95
0 1973 13.07 203 2.59 9 0 43 2 47
0 229 64.00 49 3.03 6 0 30 0 64
0 2029 13.55 154 2.04 2 0 2 2 94
If you're using the system while the dd process is running, you'll find
that anything you have open at the moment that doesn't require disk access
continues to run fine. However, as soon as vi needs to access the file
you're working on, or you call a new program from the shell prompt, the
session freezes until dd is complete.
Is there anyone familiar enough with this kind of problem that can offer
me any advise? I'm afraid this is will over my head.
--
Dan Roberts, Systems Engineer Voice 800.656.GWIS
GWIS Internet Solutions Fax 330.656.5440
Please contact support@gwis.com for all technical support issues
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