dsk/

When using DTrace to track I/Os to disks under the sd/ssd
driver, it's easy enough to  get the major/minor device
number of the disk being targeted for I/O:

fbt:ssd:ssdstrategy:entry,
fbt:sd:sdstrategy:entry
{
  io_start[(struct buf *)arg0] = timestamp;
}

fbt:ssd:ssdintr:entry,
fbt:sd:sdintr:entry
/ io_start[(this->buf = (struct buf *)((struct scsi_pkt
*)arg0)->pkt_private)]
  != 0 /
{
  this->un = ((struct sd_xbuf *)
this->buf->b_private)->xb_un;
  this->major = getmajor(this->buf->b_edev);
  this->minor = getminor(this->buf->b_edev);

  max_ms[this->major, this->minor] =
    max((timestamp - io_start[this->buf])/1000000); /*
convert ns to ms */

  io_start[this->buf] = 0;
}

We can even get device names in the form of 'ssdXXX', which
unfortunately aren't that helpful.

How can we map major/minor numbers or device names to their
/dev/[r]dsk/... symlinks in DTrace?   That would make the
output more intuitive, at least to us.

Gordon Marler
gmarlergmarler.com


--
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Gordon Marler writes:
 > When using DTrace to track I/Os to disks under the
sd/ssd driver, it's easy enough to  get the major/minor
device number of the disk being targeted for I/O:
 > 
 > fbt:ssd:ssdstrategy:entry,
 > fbt:sd:sdstrategy:entry
 > {
 >   io_start[(struct buf *)arg0] = timestamp;
 > }
 > 
 > fbt:ssd:ssdintr:entry,
 > fbt:sd:sdintr:entry
 > / io_start[(this->buf = (struct buf *)((struct
scsi_pkt *)arg0)->pkt_private)]
 >   != 0 /
 > {
 >   this->un = ((struct sd_xbuf *)
this->buf->b_private)->xb_un;
 >   this->major = getmajor(this->buf->b_edev);
 >   this->minor = getminor(this->buf->b_edev);
 > 
 >   max_ms[this->major, this->minor] =
 >     max((timestamp - io_start[this->buf])/1000000);
/* convert ns to ms */
 > 
 >   io_start[this->buf] = 0;
 > }
 > 
 > We can even get device names in the form of 'ssdXXX',
which unfortunately aren't that helpful.
 > 
 > How can we map major/minor numbers or device names to
their /dev/[r]dsk/... symlinks in DTrace?   That would make
the output more intuitive, at least to us.
 > 
 > Gordon Marler
 > gmarlergmarler.com
 > 
 > 
 > --
 > This message posted from opensolaris.org
 > _______________________________________________
 > dtrace-discuss mailing list
 > dtrace-discussopensolaris.org


Here is an example script where I got this working :


#!/usr/bin/ksh
#
# iolat - print avg latency and distribution of each disk
#
# This scripts prints average latency of each disk over the
length of the
# run. With -d, results includes an lquantization of the
result. Scripts
# runs until interrupted. Results are in usec (actually nsec
>>10).
#
# If you get "DIF program exceeds maximum program
size"
# Try : echo dtrace_dof_maxsize/Z1000000 | mdb -kw 
#

opt_dist=0; min=0; max=50000; bin=5000;

### process options
while getopts dh name
do
	case $name in
	d)	opt_dist=1 ;;
	h|?)	cat <<-END >&2
		USAGE: iolat [-d [min max bucket]]

		            -d              # report per disk latency
distribution.
		            min max bucket  # arguments to dtrace
lquantize in usec.
		                            # Default : 0, 5000, 500.
		END
		exit 1
	esac
done

shift $(( $OPTIND - 1 ))

### option logic
if [[ ! "$1" == "" ]]; then
        min=$1; shift
fi
if [[ ! "$1" == "" ]]; then
        max=$1; shift
fi
if [[ ! "$1" == "" ]]; then
        bin=$1; shift
fi

#Build a string to be parsed by dtrace
#Contains entry of the form 
#          disks[major, minor] = "c0t0d0s0"; 
#
disks_arr_string=`/bin/ls -1lL /dev/dsk/* 2>/dev/null |
/usr/bin/nawk -F'[ ,t/]*' '{print "disks[" $5
", " $6 "] = "" $12
"";"}'`

if [[ $opt_dist == 1 ]]; then
    quantize_gather="d[this->disk] =
lquantize(this->lat, $min, $max, $bin);"
    quantize_print="printf("nnLatency
Distribution:nn"); printa("%20s   %10dn", d);"
else
    quantize_gather=""
    quantize_print=""
fi


script_str='

BEGIN {
    '$disks_arr_string';
    printf("Ctrl-C to terminate and get
resultsn");
}

io:::start{
	started[args[0]->b_edev, args[0]->b_blkno] =
timestamp;
}

io:::done
/started[args[0]->b_edev, args[0]->b_blkno] != 0/
{

 
	this->major = args[1]->dev_major;
	this->minor = args[1]->dev_minor;
	this->disk = (disks[this->major, this->minor] ==
"" ? "unknown" : disks[this->major,
this->minor]);
	this->lat = (timestamp - started[args[0]->b_edev,
args[0]->b_blkno])>>10;

	a[this->disk] = avg(this->lat); /* First is
sort key */

	b[this->disk] = count();
	c[this->disk] = sum(args[0]->b_bcount);
	'$quantize_gather'

	started[args[0]->b_edev, args[0]->b_blkno] = 0;
}

END {
	printf("%20s   %10s %10s %10sn",
"Disk", "Avg Lat(us)", "IO
cnt", "Bytes"); 
        printf("%20s   %10s %10s %10sn",
"----", "----------",
"------", "-----"); 
	printa("%20s   %10d %10d %10dn", a, b, c);
	'$quantize_print'
}
'

/usr/bin/pfexec /usr/sbin/dtrace  -qn
"$script_str"


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