Re: [RFC] IO scheduler based IO controller V9

On Mon, Sep 07, 2009 at 03:40:53PM +0800, Gui Jianfeng wrote:
Hi Vivek,

I happened to encount a bug when i test IO Controller V9.
When there are three tasks to run concurrently in three group,
that is, one is parent group, and other two tasks are running
in two different child groups respectively to read or write
files in some disk, say disk "hdb", The task may hang up, and
other tasks which access into "hdb" will also hang up.

The bug only happens when using AS io scheduler.
The following scirpt can reproduce this bug in my box.


Hi Gui,

I tried reproducing this on my system and can't reproduce it. All the
three processes get killed and system does not hang.

Can you please dig deeper a bit into it.

- If whole system hangs or it is just IO to disk seems to be hung.
- Does io scheduler switch on the device work
- If the system is not hung, can you capture the blktrace on the device.
Trace might give some idea, what's happening.

Thanks
Vivek

===========
#!/bin/sh

mkdir /cgroup
mount -t cgroup -o io,blkio io /cgroup

echo anticipatory > /sys/block/hdb/queue/scheduler

mkdir /cgroup/test1
echo 100 > /cgroup/test1/io.weight

mkdir /cgroup/test2
echo 400 > /cgroup/test2/io.weight

mkdir /cgroup/test2/test3
echo 400 > /cgroup/test2/test3/io.weight

mkdir /cgroup/test2/test4
echo 400 > /cgroup/test2/test4/io.weight

#./rwio -r -f /hdb2/2000M.3 &
dd if=/hdb2/2000M.3 of=/dev/null &
pid4=$!
echo $pid4 > /cgroup/test2/test3/tasks
echo "pid4: $pid4"

#./rwio -r -f /hdb2/2000M.1 &
dd if=/hdb2/2000M.1 of=/dev/null &
pid1=$!
echo $pid1 > /cgroup/test1/tasks
echo "pid1 $pid1"

#./rwio -r -f /hdb2/2000M.2 &
dd if=/hdb2/2000M.2 of=/dev/null &
pid2=$!
echo $pid2 > /cgroup/test2/test4/tasks
echo "pid2 $pid2"

sleep 20

for ((;1;))
{
ps -p $pid1 > /dev/null 2>&1
if [ $? -ne 0 ]; then
break
fi

kill -9 $pid1 > /dev/null 2>&1
}
for ((;1;))
{
ps -p $pid2 > /dev/null 2>&1
if [ $? -ne 0 ]; then
break
fi

kill -9 $pid2 > /dev/null 2>&1
}


kill -9 $pid4 > /dev/null 2>&1

rmdir /cgroup/test2/test3
rmdir /cgroup/test2/test4
rmdir /cgroup/test2
rmdir /cgroup/test1

umount /cgroup
rmdir /cgroup
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