命令行 java 程序的磁盘 I/O

Question

I have a simple question, I've read up online but couldn't find a simple solution:

I'm running a java program on the command line as follows which accesses a database:

java -jar myProgram.jar

I would like a simple mechanism to see the number of disk I/Os performed by this program (on OSX). So far I've come across iotop but how do I get iotop to measure the disk I/O of myProgram.jar?

Do I need a profiler like JProfiler do get this information?

Answer 1

iotop is a utility which gives you top n processes in descending order of IO consumption/utilization.

Most importantly it is a live monitoring utility which means its output changes every n sec( or time interval you specify). Though you can redirect it to a file, you need to parse that file and find out meaningful data after plotting a graph.

I would recommend to use sar. you can read more about it here

It is the lowest level monitoring utility in linux/unix. It will give you much more data than iotop.

best thing about sar is you can collect the data using a daemon when your program is running and then later analyze it using ksar

According to me, you can follow below approach,

1. Start sar monitoring, collect sar data every n seconds. value of n depends of approximate execution time of your program.

example : if your program takes 10 seconds to execute then monitoring per sec is good but if your program takes 1hr to execute then monitor per min or 30 sec. This will minimize overhead of sar process and still your data is meaningful.

2. Wait for some time (so that you get data before your program starts) and then start your program

3. end of your program execution

4. wait for some time again (so that you get data after your program finishes)

5. stop sar.

Monitor/visualize sar data using ksar. To start with, you check for disk utilization and then IOPS for a disk.

You can use Profilers for same thing but they have few drawbacks,

1. They need their own agents (agents will have their own overhead)
2. Some of them are not free.
3. Some of them are not easy to set up.
4. may or may not provide enough/required data.

besides this IMHO, Using inbuilt/system level utilities is always beneficial.

I hope this was helpful.

Answer 2

Your Java program will eventually be a process for host system so you need to filter out output of monitoring tool for your own process id. Refer Scripts section of this Blog Post

Also, even though you have tagged question with OsX but do mention in question that you are using OsX.

If you are looking for offline data - that is provided by proc filesystem in Unix bases systems but unfortunately that is missing in OSX , Where is the /proc folder on Mac OS X?
/proc on Mac OS X

You might chose to write a small script to dump data from disk and process monitoring tools for your process id. You can get your process id in script by process name, put script in a loop to look for that process name and start script before you execute your Java program. When script finds the said process, it will keep dumping relevant data from commands chosen by you at intervals decided by you. Once your programs ends ,log dumping script also terminates.