DTrace on LKML

So DTrace was recently mentioned on the linux-kernel mailing list. The question in the subject was is “DTrace-like analysis possible with future Linux kernels?” The responses have been interesting. Karim Yaghmour rattled in with his usual blather about the existence of DTrace proving that LTT should have been accepted into the Linux kernel long ago. I find this argument incredibly tedious, and have addressed it at some length. Then there was this inane post:

> http://www.theregister.co.uk/2004/07/08/dtrace_user_take/:
> "Sun sees DTrace as a big advantage for Solaris over other versions of Unix
> and Linux."
That article is way too hypey.
It sounds like one of those strange american commercials you see
sometimes at night, where two overenthusiastic persons are telling you
how much that strange fruit juice machine has changed their lives,
with making them loose 200 pounds in 6 days and improving their
performance at beach volleyball a lot due to subneutronic antigravity
manipulation. You usually can't watch those commercials for longer
than 5 minutes.
The same applies to that article, I couldn't even read it completely,
it was just too much.
And is it just me or did that article really take that long to
mentioning what dtrace actually IS?
Come on, it's profiling. As presented by that article, it is even more
micro optimization than one would think. What with tweaking the disk
I/O improvements and all... If my harddisk accesses were a microsecond
more immediate or my filesystem giving a quantum more transfer rate,
it would be nice, but I certainly wouldn't get enthusiastic and I bet
nobody would even notice.
Maybe, without that article, I would recognize it as a fine thing (and
by "fine" I don't mean "the best thing since sliced bread"), but that
piece of text was just too ridiculous to take anything serious.
I sure hope that article is meant sarcastically. By the way, did I
miss something or is profiling suddenly a new thing again?
Regards,
Julien

Yes, you missed something Julien: you forgot to type “dtrace” into google. (If there were a super-nerd equivalent of the Daily Show, we might expect Lewis Black to say that – probably punctuated with his usual “you moron!”) If you had done this, you would have been taken to the DTrace BigAdmin site which contains links to the DTrace USENIX paper, the DTrace documentation, and a boatload of other material that supports the claims in The Register story. In fact, if you had just scrolled to the bottom of that story you would have read the “Bootnotes” section of the story – which provides plenty of low-level supporting detail. (Indeed, I’m not sure that I’ve ever seen The Register publish such user-supplied detail to support a story.)

Sometimes the bigotry surrounding Linux suprises even me: in the time he took to record his misconceptions, Julien could have (easily!) figured out that he was completely wrong. But I guess that even this is too much work for someone who is looking to confirm preconceived notions rather than understand new technology…

Fortunately, one of the responses did call Julien on this, if only slightly:

* Julien Oster:
> Miles Lane  writes:
>
>> http://www.theregister.co.uk/2004/07/08/dtrace_user_take/:
>> "Sun sees DTrace as a big advantage for Solaris over other versions of Unix
>> and Linux."
>
> That article is way too hypey.
Maybe, but DTrace seems to solve one really pressing problem: tracking
disk I/O to the processes causing it.  Unexplained high I/O
utilization is a *very* common problem, and there aren't any tools to
diagnose it.
Most other system resources can be tracked quite easily: disk space,
CPU time, committed address space, even network I/O (with tcpdump and
netstat -p).  But there's no such thing for disk I/O.

Of course, the responder misses the larger point about DTrace – that one can instrument one’s system arbitrarily and safely with DTrace – but at least he correctly identifies one capacity in which DTrace clearly leads the pack. And I suppose that this is the best that a rival technology can expect to do, so close to the epicenter of Linux development…