DTrace for Cocoa Developers

Update: Sorry people I didn't know the default Viddler downloading permissions. If you logged in and tried to download the video and couldn't before, login again and you should be able to download it now.

So in this Screencast Im going to show you how to use DTrace and how to ultimately turn that knowledge into a custom DTrace Instrument for Instruments. Honestly I would login and download the full quality version of this from Viddler. I apologize for the hisses in the s's that I make, I was slightly tired and trying to control that. As always if I said something wrong and made a mistake please let me know right away and i'll make a correction here.



DTrace Examples in the movie

Example #1

colinw$ sudo dtrace -n 'syscall:::/execname == "Safari"/{@num[probefunc] = count();}' -q
^C

lstat 2
sigaltstack 2
sigprocmask 2
stat 2
getuid 16
mmap 32
munmap 36
geteuid 94
gettimeofday 128
stat64 248


Example #2

colinw$ sudo dtrace -n 'syscall::*open*:entry{printf("%s %s",execname,copyinstr(arg0));}'
dtrace: description 'syscall::*open*:entry' matched 7 probes
CPU ID FUNCTION:NAME
0 17604 open:entry mds .
1 17604 open:entry nmbd /private/var/samba/browse.dat.
0 17604 open:entry Safari /.vol/234881026/1644952
1 17604 open:entry mdworker /private/var/samba/browse.dat
1 17604 open:entry mds .
1 17604 open:entry Safari /.vol/234881026/230745/QuickTime Preferences
^C


Example #3

colinw$ sudo dtrace -n 'syscall:::/execname == "Safari"/{@num[ustack()] = count();}' -q
Password:
^C

libSystem.B.dylib`sendto$UNIX2003+0xa
CoreFoundation`__CFSocketEnableCallBacks+0x255
CoreFoundation`CFSocketEnableCallBacks+0x4f
CFNetwork`_SocketStreamRead+0x5e5
CoreFoundation`CFReadStreamRead+0x1dd
CFNetwork`httpRdFilterRead+0x5ef
CoreFoundation`CFReadStreamRead+0x1dd
CFNetwork`httpStreamRead+0x2aa
CoreFoundation`CFReadStreamRead+0x1dd
CFNetwork`httpReadStreamCB+0x94
CoreFoundation`_CFStreamSignalEventSynch+0x89
CoreFoundation`CFRunLoopRunSpecific+0xca8
CoreFoundation`CFRunLoopRunInMode+0x58
Foundation`+[NSURLConnection(NSURLConnectionReallyInternal) _resourceLoadLoop:]+0x140
Foundation`-[NSThread main]+0x2d
Foundation`__NSThread__main__+0x134
libSystem.B.dylib`_pthread_start+0x141
libSystem.B.dylib`thread_start+0x22
2

Example #4

sh-3.2# dtrace -n 'objc16675:NSMutableArray::entry{@num[ustack()] = count();}'
dtrace: description 'objc16675:NSMutableArray::entry' matched 24 probes
^C


CoreFoundation`+[NSMutableArray arrayWithCapacity:]
Keynote`0x201ab
Keynote`0x35289
Keynote`0x9d981
AppKit`-[NSWindow makeFirstResponder:]+0x12e
Keynote`0xa1b29
AppKit`-[NSWindow sendEvent:]+0x1505
Keynote`0x18c7e7
AppKit`-[NSApplication sendEvent:]+0xadc
SFApplication`-[SFAppApplication sendEvent:]+0x283
Keynote`0x26d69
AppKit`-[NSApplication run]+0x34f
Keynote`0x352f
Keynote`0x34a5
Keynote`0x4cc36
Keynote`0x4cb5d
0x2
1

Useful DTrace Links
Solaris DTrace Guide (PDF) from Sun
Solaris DTrace Guide (HTML) from Sun
DTrace Review (Google Tech Talk)
MacTech: Exploring Leopard with DTrace

I am on the Mac Developer Roundtable 007 Source Code Management

I was an invited guest on the Mac Developer Roundtable and came on to talk Source Code Management and to advocate for GIT. It was my first time ever on a podcast and I was a bit nervous, still listening to the first part of it right now, but it sounds pretty good so far. Please forgive all the "uhs" I do, Im normally a lot more confident speaking publicly, but I didn't know what to expect on the podcast.

Give it a listen and let me know what you think. Be gentle, it's my first time :P ...

Mac Developer Roundtable Episode 007 - Source Code Management

My Recommendations from the podcast

F-Script
If I remember correctly, I think I just glanced over F-Script and didn't give it much explanation. Im a huge fan of creating experimental projects and playing around with API's and that's one reason Im a fan of F-Script because then I don't have 30 small projects cluttering up my desktop or a temp directory and so now I do much less tiny projects in Xcode and use F-Script to see how the API's work. You can start F-Script up in a console and create an app from scratch or just create temp objects and see how they work and play around with Cocoa in a way that's not possible in Xcode without creating loads of small projects.

You can download F-Script from http://www.fscript.org/ though if you are on Leopard you will need to download and install a special version of FScript Anywhere from http://osiris.laya.com/blog/?p=24

Mac OS X Internals
Mac OS X Internals is a great book explaining the guts of Mac OS X and its individual components to you in how they work and comes with many source code examples to demo what's going on. It's a very big book, but it's well worth it for the content it offers you. The books website is at http://www.osxbook.com/