#!/bin/bash
#
# perf-stat-hist - perf_events stat histogram hack.
#                  Written using Linux perf_events (aka "perf").
#
# This is a proof-of-concept showing in-kernel histogram summaries of a
# tracepoint variable.
#
# USAGE: perf-stat-hist [-h] [-b buckets|-P power] [-m max] tracepoint
#        variable [seconds]
#
# Run "perf-stat-hist -h" for full usage.
#
# This uses multiple counting tracepoints with different filters, one for each
# histogram bucket. While this is summarized in-kernel, the use of multiple
# tracepoints does add addiitonal overhead, which is more evident if you change
# the power-of size from 4 to 2 (which creates more buckets). Hopefully, in the
# future this this functionality will be provided in an efficient way from
# perf_events itself, at which point this tool can be rewritten.
#
# From perf-tools: https://github.com/brendangregg/perf-tools
# 
# COPYRIGHT: Copyright (c) 2014 Brendan Gregg.
#
#  This program is free software; you can redistribute it and/or
#  modify it under the terms of the GNU General Public License
#  as published by the Free Software Foundation; either version 2
#  of the License, or (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  You should have received a copy of the GNU General Public License
#  along with this program; if not, write to the Free Software Foundation,
#  Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
#
#  (http://www.gnu.org/copyleft/gpl.html)
#
# 30-Jun-2014	Brendan Gregg	Created this.

opt_buckets=0; buckets=; opt_power=0; power=4; opt_max=0; max=$((1024 * 1024))
opt_filter=0; filter=; duration=0; debug=0
trap ':' INT QUIT TERM PIPE HUP

function usage {
	cat <<-END >&2
	USAGE: perf-stat-hist [-h] [-b buckets|-P power] [-m max] [-f filter]
	                      tracepoint variable [seconds]
	                 -b buckets      # specify histogram bucket points
	                 -P power        # power-of (default is 4)
	                 -m max          # max value for power-of
	                 -f filter       # specify a filter 
	                 -h              # this usage message
	   eg,
	       perf-stat-hist syscalls:sys_enter_read count 5
	                 # read() request histogram, 5 seconds
	       perf-stat-hist syscalls:sys_exit_read ret 5
	                 # read() return histogram, 5 seconds
	       perf-stat-hist -P 10 syscalls:sys_exit_read ret 5
	                 # ... use power-of-10
	       perf-stat-hist -P 2 -m 1024 syscalls:sys_exit_read ret 5
	                 # ... use power-of-2, max 1024
	       perf-stat-hist -b "10 50 100 500" syscalls:sys_exit_read ret 5
	                 # ... histogram based on these bucket ranges
	       perf-stat-hist -b 10 syscalls:sys_exit_read ret 5
	                 # ... bifurcate by the value 10 (lowest overhead)
	       perf-stat-hist -f 'rwbs == "WS"' block:block_rq_complete nr_sector 5
	                 # ... synchronous writes histogram, 5 seconds

	See the man page and example file for more info.
END
	exit
}

function die {
	echo >&2 "$@"
	exit 1
}

### process options
while getopts b:hm:P:f: opt
do
	case $opt in
	b)	opt_buckets=1; buckets=($OPTARG) ;;
	P)	opt_power=1; power=$OPTARG ;;
	m)	opt_max=1; max=$OPTARG ;;
	f)	opt_filter=1; filter="$OPTARG && " ;;
	h|?)	usage ;;
	esac
done
shift $(( $OPTIND - 1 ))
(( $# < 2 )) && usage
tpoint=$1			# tracepoint
var=$2				# variable for histogram
duration=${3}

### option logic
(( opt_buckets && opt_power )) && die "ERROR: use either -b or -P"
(( opt_power && power < 2 )) && die "ERROR: -P power must be 2 or higher"

### check that tracepoint exists
if ! grep "^$tpoint\$" /sys/kernel/debug/tracing/available_events > /dev/null
then
	echo >&2 "ERROR: tracepoint \"$tpoint\" not found. Exiting..."
	[[ "$USER" != "root" ]] && echo >&2 "Not root user?"
	exit 1
fi

### auto build power-of buckets
if (( !opt_buckets )); then
	b=0
	s=1
	while (( s <= max )); do
		b="$b $s"
		(( s *= power ))
	done
	buckets=($b)
fi

### build list of tracepoints and filters for each histogram bucket
max=${buckets[${#buckets[@]} - 1]}	# last element
((max_i = ${#buckets[*]} - 1))
tpoints="-e $tpoint --filter \"$filter $var < ${buckets[0]}\""
awkarray=
i=0
while (( i < max_i )); do
	if (( i && ${buckets[$i]} <= ${buckets[$i - 1]} )); then
		die "ERROR: bucket list must increase in size."
	fi
	tpoints="$tpoints -e $tpoint --filter \"$filter $var >= ${buckets[$i]} && "
	tpoints="$tpoints $var < ${buckets[$i + 1]}\""
	awkarray="$awkarray buckets[$i]=${buckets[$i]};"
	(( i++ ))
done
awkarray="$awkarray buckets[$max_i]=${buckets[$max_i]};"
tpoints="$tpoints -e $tpoint --filter \"$filter $var >= ${buckets[$max_i]}\""

if (( debug )); then
	echo buckets: ${buckets[*]}
	echo tracepoints: $tpoints
	echo awkarray: ${awkarray[*]}
fi

### prepare to run
if (( duration )); then
	etext="for $duration seconds"
	cmd="sleep $duration"
else
	etext="until Ctrl-C"
	cmd="sleep 999999"
fi

p_tpoint=$tpoint
if [ -n "$filter" ]; then 
	p_tpoint="$tpoint (Filter: ${filter%????})"
fi

if (( opt_buckets )); then
	echo "Tracing $p_tpoint, specified buckets, $etext..."
else
	echo "Tracing $p_tpoint, power-of-$power, max $max, $etext..."
fi

### run perf
out="-o /dev/stdout"	# a workaround needed in linux 3.2; not by 3.4.15
stat=$(eval perf stat $tpoints -a $out $cmd 2>&1)
if (( $? != 0 )); then
	echo >&2 "ERROR running perf:"
	echo >&2 "$stat"
	exit
fi

if (( debug )); then
	echo raw output:
	echo "$stat"
	echo
fi

### find max value for ASCII histogram
most=$(echo "$stat" | awk -v tpoint=$tpoint '
	$2 == tpoint { gsub(/,/, ""); if ($1 > m) { m = $1 } }
	END { print m }'
)

### process output
echo
echo "$stat" | awk -v tpoint=$tpoint -v max_i=$max_i -v most=$most '
	function star(sval, smax, swidth) {
		stars = ""
		if (smax == 0) return ""
		for (si = 0; si < (swidth * sval / smax); si++) {
			stars = stars "#"
		}
		return stars
	}
	BEGIN {
		'"$awkarray"'
		printf("            %-15s: %-8s %s\n", "Range", "Count",
		    "Distribution")
	}
	/Performance counter stats/ { i = -1 }
	# reverse order of rule set is important
	{ ok = 0 }
	$2 == tpoint { num = $1; gsub(/,/, "", num); ok = 1 }
	ok && i >= max_i {
		printf("   %10d -> %-10s: %-8s |%-38s|\n", buckets[i],
		    "", num, star(num, most, 38))
		next
	}
	ok && i >= 0 && i < max_i {
		printf("   %10d -> %-10d: %-8s |%-38s|\n", buckets[i],
		    buckets[i+1] - 1, num, star(num, most, 38))
		i++
		next
	}
	ok && i == -1 {
		printf("   %10s -> %-10d: %-8s |%-38s|\n", "",
		    buckets[0] - 1, num, star(num, most, 38))
		i++
	}
'