On 12/11/12 23:46, scameron@xxxxxxxxxxxxxxxxxx wrote:
I would be curious to see what kind of results you would get with scsi_debug
with fake_rw=1. I am sort of suspecting that trying to put an "upper limit"
on scsi LLD IOPS performance by seeing what scsi_debug will do with fake_rw=1
is not really valid (or, maybe I'm doing it wrong) as I know of one case in
which a real HW scsi driver beats scsi_debug fake_rw=1 at IOPS on the very
same system, which seems like it shouldn't be possible. Kind of mysterious.
The test
# disable-frequency-scaling
# modprobe scsi_debug delay=0 fake_rw=1
# echo 2 > /sys/block/sdc/queue/rq_affinity
# echo noop > /sys/block/sdc/queue/scheduler
# echo 0 > /sys/block/sdc/queue/add_random
results in about 800K IOPS for random reads on the same setup (with a
request size of 4 KB; CPU: quad core i5-2400).
Repeating the same test with fake_rw=0 results in about 651K IOPS.
Bart.
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