DTrace on Linux

Linux port of DTrace has been moving for some time now.

I just tried the latest bits from ftp://crisp.dynalias.com/pub/release/website/dtrace and the initial impression is we got really cool stuff (in the making here).

Besides, GCC, Kernel headers, you will need the following stuffs to compile and load the DTrace kernel module:

• libelf-dev: Working with 'elf' files
• zlib libraries: working with the zlib files
• bison, flex

Once you have got them, extract the sources and do:

1. make all
2. sudo make install
3. sudo make load

If you do not see any error message, then the DTrace kernel module 'dtracedrv' has been correctly insrted.dtrace -l should display a long list of the currently available probes.

Let's try a simple DTrace one-liner.

This DTrace one-liner dtrace -n 'syscall:::entry { @num[probefunc] = count(); } will display the number of times a system call is invoked during the time its running. Press a C-c after sometime and you should see something like this:

amit@kubuntu904:~$ dtrace -n 'syscall:::entry { @num[probefunc] = count(); }'
dtrace: description 'syscall:::entry ' matched 329 probes
dtrace: buffer size lowered to 512k
dtrace: aggregation size lowered to 256k
^C


kill                                                              1
rt_sigpending                                                     1
readlink                                                          2
sigprocmask                                                       2
brk                                                               3
uname                                                             3
lstat64                                                           5
fcntl64                                                           7
sigreturn                                                         7
close                                                            11
open                                                             11
socketcall                                                       11
_llseek                                                          14
munmap                                                           15
rt_sigaction                                                     16
mmap2                                                            19
access                                                           27
rt_sigprocmask                                                   30
stat64                                                           54
fstat64                                                          69
setitimer                                                       230
writev                                                          397
time                                                            482
_newselect                                                      545
write                                                           709
futex                                                           727
ioctl                                                           754
poll                                                           1583
gettimeofday                                                   2212
read                                                           4878
clock_gettime                                                  5462

That's all for now. I just wanted to post my initial excitement :-)

Some points:

1. If your OS seems to hang after the DTrace command, and even a C-c/ C-d/ C-z won't help, then its possibly an issue with the terminal you are using. I had issues with gnome-terminal, xterm and ETerm. However, it works perfectly on KDE's konsole
   
2. If you are using Debian 5, you will possibly need to recompile your kernel for the zlib symbols in the kernel
   
3. If you are familiar with DTrace on Solaris, you must have noticed that I could use DTrace as non-root user, this is different from the way it works on Solaris. I shall try to explore more on this.