blktrace version v2.0.0
note: in blkparse output, the m in the sixth column indicate the line is scheduler information.
On Ubuntu 16.04 ext4 I can see the IO Scheduler message, blktrace -d /dev/sda -o - | blkparse -i -
8,0 3 1 0.000000000 24714 A WS 76519424 + 2048 <- (8,1) 76517376
8,0 3 2 0.000000861 24714 Q WS 76519424 + 2048 [TaskSchedulerFo]
8,0 3 3 0.000005084 24714 X WS 76519424 / 76520768 [TaskSchedulerFo]
8,0 3 4 0.000008962 24714 G WS 76519424 + 1344 [TaskSchedulerFo]
8,0 3 5 0.000009379 24714 P N [TaskSchedulerFo]
8,0 3 6 0.000012021 24714 G WS 76520768 + 704 [TaskSchedulerFo]
8,0 3 7 0.000012622 24714 I WS 76519424 + 1344 [TaskSchedulerFo]
8,0 3 0 0.000015209 0 m N cfq24714SN /user.slice insert_request
8,0 3 0 0.000016074 0 m N cfq24714SN /user.slice add_to_rr
8,0 3 0 0.000017548 0 m N cfq24714SN /user.slice preempt
8,0 3 0 0.000018184 0 m N cfq25055SN /user.slice slice expired t=1
8,0 3 0 0.000018982 0 m N cfq25055SN /user.slice resid=-2643710186
8,0 3 0 0.000020125 0 m N /user.slice served: vt=247310740068 min_vt=247310580285
8,0 3 0 0.000021297 0 m N cfq25055SN /user.slice sl_used=33325195 disp=13 charge=13 iops=1 sect=1088
8,0 3 0 0.000021822 0 m N cfq25055SN /user.slice del_from_rr
8,0 3 0 0.000023767 0 m N cfq workload slice:100000000
8,0 3 0 0.000024496 0 m N cfq24714SN /user.slice set_active wl_class:0 wl_type:1
8,0 3 0 0.000025395 0 m N cfq24714SN /user.slice dispatch_insert
8,0 3 0 0.000026232 0 m N cfq24714SN /user.slice dispatched a request
8,0 3 0 0.000026818 0 m N cfq24714SN /user.slice activate rq, drv=1
8,0 3 8 0.000027030 24714 D WS 76519424 + 1344 [TaskSchedulerFo]
8,0 3 9 0.000037848 24714 U N [TaskSchedulerFo] 1
8,0 3 10 0.000038118 24714 P N [TaskSchedulerFo]
8,0 3 11 0.000048153 24714 A WS 76521472 + 264 <- (8,1) 76519424
8,0 3 12 0.000048340 24714 Q WS 76521472 + 264 [TaskSchedulerFo]
8,0 3 13 0.000049444 24714 M WS 76521472 + 264 [TaskSchedulerFo]
8,0 3 14 0.000050486 24714 I WS 76520768 + 968 [TaskSchedulerFo]
8,0 3 0 0.000051332 0 m N cfq24714SN /user.slice insert_request
8,0 3 15 0.000051755 24714 U N [TaskSchedulerFo] 1
8,0 3 0 0.000052418 0 m N cfq24714SN /user.slice dispatch_insert
8,0 3 0 0.000053068 0 m N cfq24714SN /user.slice dispatched a request
8,0 3 0 0.000053604 0 m N cfq24714SN /user.slice activate rq, drv=2
8,0 3 16 0.000053721 24714 D WS 76520768 + 968 [TaskSchedulerFo]
8,0 2 1 0.001844211 0 C WS 76519424 + 1344 [0]
8,0 2 0 0.001849143 0 m N cfq24714SN /user.slice complete rqnoi
on CentOS 7.4 xfs,I can not see the IO Scheduler message, blktrace -d /dev/sdb -o - | blkparse -i -
8,16 25 1 0.000000000 11966 Q R 73400472 + 128 [fio]
8,16 25 2 0.000006237 11966 G R 73400472 + 128 [fio]
8,16 25 3 0.000007806 11966 P N [fio]
8,16 25 4 0.000010836 11966 I R 73400472 + 128 [fio]
8,16 25 5 0.000011878 11966 U N [fio] 1
8,16 25 6 0.000013900 11966 D R 73400472 + 128 [fio]
8,16 10 1 0.008284979 0 C R 73400472 + 128 [0]
8,16 10 2 0.008343574 11966 Q R 73400600 + 128 [fio]
8,16 10 3 0.008345976 11966 G R 73400600 + 128 [fio]
8,16 10 4 0.008346908 11966 P N [fio]
8,16 10 5 0.008348926 11966 I R 73400600 + 128 [fio]
8,16 10 6 0.008349651 11966 U N [fio] 1
8,16 10 7 0.008350694 11966 D R 73400600 + 128 [fio]
8,16 8 1 0.008771249 0 C R 73400600 + 128 [0]
While there are program version differences between the setups (in CentOS 7 blktrace is version 1.0.5 and the kernel is based off 3.10 whereas in Ubuntu 16.04 blktrace is version 1.1.0 and the kernel may be between 4.4 - 4.10) the real point may be down to what was asked (but unfortunately went unanswered) in one of the comments:
what [I/O] scheduler was in use
If we look at one of your m lines:
8,0 3 0 0.000015209 0 m N cfq24714SN /user.slice insert_request
we can see that it is a textual message (hence the m) and that it likely came from the CFQ I/O scheduler (hence the cfq prefix on the message itself). If the I/O scheduler being used for the /dev/sdb device on the CentOS 7 setup was not CFQ (e.g. because the noop I/O scheduler was being used) then we cannot expect similar messages to be present.
So bringing this back to the title of the question:
blkparse how to show IO Scheduler message
If an I/O scheduler wants to it can send free form blktrace text (e.g. see block/cfq-iosched.c which has calls to blk_add_trace_msg() in it) but not all I/O schedulers do (e.g. see block/noop-iosched.c which doesn't even include the linux/blktrace_api.h header). By default blkparse will show all messages present unless you use the -M option to suppress them.