#!/bin/bash

######################################################################
# customize per survey

# the SG device to measure
dev=/dev/sg6

# result file prefix
# NB ensure the path exists if it includes subdirs
rslt=/tmp/sg_dd_rslt

# what to do (read or write)
action=write

# total size (MBytes)
# NB bigger than device cache is good
size=8192

# record size (KBytes)
rszlo=1024
rszhi=1024

# Concurrent regions
crglo=1
crghi=4

# total numbers of threads to share between concurrent regions
# NB survey skips over #thr < #regions
thrlo=1
thrhi=1024

#####################################################################

# disk block size (Bytes)
bs=512

if [ $action = read ]; then
    f1="if=$dev"
    f2="of=/dev/null"
    skip=skip
else
    f1="if=/dev/zero"
    f2="of=$dev"
    skip=seek
fi

start=`date +%F@%R`
rsltf=${rslt}_${start}.summary
echo -n > $rsltf
workf=${rslt}_${start}.detail
echo -n > $workf

print_summary () {
    if [ "$1" = "-n" ]; then
	minusn=$1; shift
    else
	minusn=""
    fi
    echo $minusn "$*" >> $rsltf
    echo $minusn "$*"
}

for ((rsz=$rszlo;rsz<=$rszhi;rsz*=2)); do
    for ((crg=$crglo;crg<=$crghi;crg*=2)); do 
	for ((thr=$thrlo;thr<=$thrhi;thr*=2)); do
	    if ((thr < crg)); then
		continue
	    fi
	    # compute parameters
	    bpt=$((rsz*1024/bs))
	    blocks=$((size*((1024*1024)/bs)/crg))
	    count=$blocks
	    # show computed parameters
	    actual_rsz=$((bpt*bs/1024))
	    actual_size=$((bs*count*crg/1024))
	    str=`printf 'total_size %8dK rsz %4d crg %5d thr %3d ' \
		         $actual_size $actual_rsz $crg $thr`
	    echo "==============> $str" >> $workf
	    print_summary -n "$str"
	    freemem=`awk < /proc/meminfo '/^MemTotal:/ {printf "%d\n", $2}'`
	    if (((actual_rsz * thr /crg + 64) * crg > freemem)); then
		print_summary "ENOMEM"
		continue
	    fi
	    # start test
	    t0=`date +%s.%N`
	    for ((i=0;i<crg;i++)); do 
		sgp_dd 2> ${rslt}_tmp${i} \
		    $f1 $f2 ${skip}=$((1024+i*blocks)) \
		    thr=$((thr/crg)) count=$count bs=$bs bpt=$bpt time=1&
	    done 
	    wait
	    t1=`date +%s.%N`
	    # collect all results in 1 file
	    rfile=${rslt}_thr${thr}_crg${crg}_rsz${rsz}
	    echo > $rfile
	    ok=0
	    for ((i=0;i<crg;i++)); do
		rtmp=${rslt}_tmp${i}
		if grep 'time to transfer data' $rtmp > /dev/null 2>&1; then
		    ok=$((ok + 1))
		fi
		cat ${rslt}_tmp${i} >> $rfile
		cat ${rslt}_tmp${i} >> $workf
		rm ${rslt}_tmp${i}
	    done
	    if [ $ok -ne $crg ]; then
		print_summary `printf "failed %d" $((crg - ok))`
	    else
	        # compute MB/sec from elapsed
		bw=`awk "BEGIN {printf \"%6.2f MB/s\", $actual_size / (( $t1 - $t0 ) * 1024); exit}"`
	        # compute MB/sec from nregions*slowest
		check=`awk < $rfile \
		           '/time to transfer data/ {mb=$8/1.048576; if (n == 0 || mb < min) min = mb; n++}\
		            END {printf "%3d x %6.2f = %6.2f MB/s", n, min, min * n}'`
                print_summary "$bw $check"
	    fi
	    rm $rfile
	done
    done
done