#!/bin/bash

DEVS=sda # please set this parameter to the dev name for your test drive

SCHED=bfq
TRACE=1

function init_tracing {
	if [ "$TRACE" == "1" ] ; then
		if [ ! -d /sys/kernel/debug/tracing ] ; then
			mount -t debugfs none /sys/kernel/debug
		fi
		echo nop > /sys/kernel/debug/tracing/current_tracer
		echo 500000 > /sys/kernel/debug/tracing/buffer_size_kb
		echo "${SCHED}*" "__${SCHED}*" >\
			/sys/kernel/debug/tracing/set_ftrace_filter
		echo blk > /sys/kernel/debug/tracing/current_tracer
	fi
}

function set_tracing {
	if [ "$TRACE" == "1" ] ; then
	    if [[ -e /sys/kernel/debug/tracing/tracing_enabled && \
		$(cat /sys/kernel/debug/tracing/tracing_enabled) -ne $1 ]]; then
			echo "echo $1 > /sys/kernel/debug/tracing/tracing_enabled"
			echo $1 > /sys/kernel/debug/tracing/tracing_enabled
		fi
		dev=$(echo $DEVS | awk '{ print $1 }')
		if [[ -e /sys/block/$dev/trace/enable && \
			  $(cat /sys/block/$dev/trace/enable) -ne $1 ]]; then
		    echo "echo $1 > /sys/block/$dev/trace/enable"
		    echo $1 > /sys/block/$dev/trace/enable
		fi

		if [ "$1" == 0 ]; then
		    for cpu_path in /sys/kernel/debug/tracing/per_cpu/cpu?
		    do
			stat_file=$cpu_path/stats
			OVER=$(grep "overrun" $stat_file | \
			    grep -v "overrun: 0")
			if [ "$OVER" != "" ]; then
			    cpu=$(basename $cpu_path)
			    echo $OVER on $cpu, please increase buffer size!
			fi
		    done
		fi
	fi
}

init_tracing

mkdir /sys/fs/cgroup/blkio/testgrp
echo $BASHPID > /sys/fs/cgroup/blkio/testgrp/cgroup.procs
echo > /sys/kernel/debug/tracing/trace
set_tracing 1 
echo bfq > /sys/block/sda/queue/scheduler
cat /sys/block/sda/queue/scheduler
echo 0 > /sys/block/sda/queue/iosched/low_latency
dd if=/dev/zero of=/root/test.img bs=512 count=5000 oflag=dsync
set_tracing 0
echo 1 > /sys/block/sda/queue/iosched/low_latency
cp /sys/kernel/debug/tracing/trace .
echo $BASHPID > /sys/fs/cgroup/blkio/cgroup.procs 
rmdir /sys/fs/cgroup/blkio/testgrp