DTrace and MySQL - 1

With this post, I am starting another series of blog posts that will help you become familiar of DTrace. You can then apply that knowledge to find all the hidden performance goodies of MySQL on Solaris 10. Sounds good?

DTrace is one of those tools that the more you use it, the more you fall in love with it. To be fair, it is much more than a tool, in fact it has its own language, D.

With DTrace you can enable probes by either their name or their number. To see a list of probes available, run

[root@db31:/] dtrace -l | more
   ID   PROVIDER            MODULE                          FUNCTION NAME
    1     dtrace                                                     BEGIN
    2     dtrace                                                     END
    3     dtrace                                                     ERROR
    4    syscall                                               nosys entry
    5    syscall                                               nosys return
    6    syscall                                               rexit entry
    7    syscall                                               rexit return
    8    syscall                                             forkall entry
    9    syscall                                             forkall return
   10    syscall                                                read entry
   11    syscall                                                read return
   12    syscall                                               write entry
   13    syscall                                               write return
   14    syscall                                                open entry
   15    syscall                                                open return
   16    syscall                                               close entry
   17    syscall                                               close return
   18    syscall                                                wait entry
   19    syscall                                                wait return
   20    syscall                                               creat entry
   21    syscall                                               creat return
...

.

To enable a basic probe named BEGIN with the id of 1, we can either use:

[root@db31:/] dtrace -n BEGIN
dtrace: description 'BEGIN' matched 1 probe
CPU     ID                    FUNCTION:NAME
  1      1                           :BEGIN
^C

or

[root@db31:/] dtrace -i 1
dtrace: description '1' matched 1 probe
CPU     ID                    FUNCTION:NAME
  0      1                           :BEGIN
^C

In addition, to enabling individual probes, we can also enable multiple probes simply be specifying them on the command line. For instance:

[root@db31:/] dtrace -i 1 -i 2 -i 3
dtrace: description '1' matched 1 probe
dtrace: description '2' matched 1 probe
dtrace: description '3' matched 1 probe
CPU     ID                    FUNCTION:NAME
  0      1                           :BEGIN
^C
  0      2                             :END

or

[root@db31:/] dtrace -n BEGIN -n END -n ERROR
dtrace: description 'BEGIN' matched 1 probe
dtrace: description 'END' matched 1 probe
dtrace: description 'ERROR' matched 1 probe
CPU     ID                    FUNCTION:NAME
  1      1                           :BEGIN
^C
  0      2                             :END

If you try to enable a probe that is not valid, you will get an error like this:

[root@db31:/] dtrace -n BEGIN -n END -n ERRORS
dtrace: invalid probe specifier ERRORS: probe description :::ERRORS does not match any probes

For a complete and in-depth coverage of DTrace, make sure you check out Solaris Dynamic Tracing Guide. For those looking to dive into examples right away, checkout the /usr/demo/dtrace directory on your Solaris machine.

to be continued...