On Tue, 27 Aug 2013 18:03:25 -0400
Jörn Engel <joern@xxxxxxxxx> wrote:
> Here is a fun patch in an early state. Essentially I want to trace
> scsi commands, which has already been done long ago. The problem I
> have is that I care about all the scsi commands for one particular
> device - without knowing in advance which device it will be. Once I
> know the device in question, I want to dump the last X commands.
Is the device passed to the trace point? If so, you can add a filter on
that device. You can even create a separate buffer to just trace that
device.
cd /sys/kernel/debug/tracing
mkdir instances/myscsi
echo 'channel==0 && id==0 && lun==0' > \
instances/myscsi/events/scsi/scsi_dispatch_cmd_done/filter
echo 1 > instance/myscsi/events/scsi/scsi_dispatch_cmd_done/enable
cat instances/myscsi/trace
# tracer: nop
#
# entries-in-buffer/entries-written: 10/10 #P:4
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / delay
# TASK-PID CPU# |||| TIMESTAMP FUNCTION
# | | | |||| | |
<idle>-0 [000] d.h3 8173.344559: scsi_dispatch_cmd_done: host_no=0 channel=0 id=0 lun=0 data_sgl=1 prot_sgl=0 prot_op=SCSI_PROT_NORMAL cmnd=(READ_10 lba=68117912 txlen=8 protect=0 raw=28 00 04 0f 65 98 00 00 08 00) result=(driver=DRIVER_OK host=DID_OK message=COMMAND_COMPLETE status=SAM_STAT_GOOD)
<idle>-0 [001] d.h3 8173.347743: scsi_dispatch_cmd_done: host_no=0 channel=0 id=0 lun=0 data_sgl=1 prot_sgl=0 prot_op=SCSI_PROT_NORMAL cmnd=(READ_10 lba=68351144 txlen=8 protect=0 raw=28 00 04 12 f4 a8 00 00 08 00) result=(driver=DRIVER_OK host=DID_OK message=COMMAND_COMPLETE status=SAM_STAT_GOOD)
<idle>-0 [000] d.h3 8174.810108: scsi_dispatch_cmd_done: host_no=0 channel=0 id=0 lun=0 data_sgl=1 prot_sgl=0 prot_op=SCSI_PROT_NORMAL cmnd=(READ_10 lba=61301272 txlen=8 protect=0 raw=28 00 03 a7 62 18 00 00 08 00) result=(driver=DRIVER_OK host=DID_OK message=COMMAND_COMPLETE status=SAM_STAT_GOOD)
<idle>-0 [001] d.h3 8174.822038: scsi_dispatch_cmd_done: host_no=0 channel=0 id=0 lun=0 data_sgl=1 prot_sgl=0 prot_op=SCSI_PROT_NORMAL cmnd=(READ_10 lba=48718352 txlen=8 protect=0 raw=28 00 02 e7 62 10 00 00 08 00) result=(driver=DRIVER_OK host=DID_OK message=COMMAND_COMPLETE status=SAM_STAT_GOOD)
<idle>-0 [002] d.h3 8174.827439: scsi_dispatch_cmd_done: host_no=0 channel=0 id=0 lun=0 data_sgl=1 prot_sgl=0 prot_op=SCSI_PROT_NORMAL cmnd=(READ_10 lba=56582672 txlen=8 protect=0 raw=28 00 03 5f 62 10 00 00 08 00) result=(driver=DRIVER_OK host=DID_OK message=COMMAND_COMPLETE status=SAM_STAT_GOOD)
<idle>-0 [003] d.h3 8174.835280: scsi_dispatch_cmd_done:
host_no=0 channel=0 id=0 lun=0 data_sgl=1 prot_sgl=0
prot_op=SCSI_PROT_NORMAL cmnd=(READ_10 lba=82010640 txl
Is that something you are talking about?
-- Steve
>
> The existing tracing is covering all commands to all devices. So
> either I have to oversize my trace buffer and dump way too much, or I
> will miss the stuff I am interested in most of the time. Hence my
> per-device trace buffer (called fdr to avoid namespace collisions).
>
> Steven, is there some magic 2-line patch that would also give me what
> I want without having to reinvent all your infrastructure and doing
> such a bad job?
>
> Jörn
>
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