[dm-devel] [Question] btt -B doesn't output anything with DM device
Akira Hayakawa
ruby.wktk at gmail.com
Thu Dec 5 12:12:49 UTC 2013
Hi, Guys,
I am trying to visualize io pattern by bno_plot.
bno_plot requires an output from btt -B but
btt -B doesn't output anything for DM devices (e.g. /dev/mapper/mydev) while
it does for real block devices (e.g. /dev/sdc).
For narrowing down the problem
I reproduced this problem with simple linear device.
# Setup
root at Freedom:/home/akira# dmsetup create mydev --table "0 100000 linear /dev/sdc 0"
root at Freedom:/home/akira# dmsetup ls
pdc_fgaahfadb (254:0)
mydev (254:1) <- this
# Trace
root at Freedom:/home/akira# cat devlist
/dev/mapper/mydev
/dev/sdc
root at Freedom:/home/akira# blktrace -w 30 -I devlist -D mytrace
=== dm-1 ===
CPU 0: 0 events, 0 KiB data
CPU 1: 378 events, 18 KiB data
Total: 378 events (dropped 0), 18 KiB data
=== sdc ===
CPU 0: 0 events, 0 KiB data
CPU 1: 781 events, 37 KiB data
Total: 781 events (dropped 0), 37 KiB data
root at Freedom:/home/akira# ls mytrace/
dm-1.blktrace.0 dm-1.blktrace.1 sdc.blktrace.0 sdc.blktrace.1
# btt
root at Freedom:/home/akira# btt -i mytrace/sdc.blktrace.* -B sdc
root at Freedom:/home/akira# btt -i mytrace/dm-1.blktrace.* -B dm-1
root at Freedom:/home/akira# ls *.dat
sdc_008,032_c.dat sdc_008,032_r.dat
btt doesn't output anything with dm-1.blktrace.* .
Is this intentionally designed or just a (known/unknown) bug?
Or, do I forget something?
Thanks,
Akira
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