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Tag: DTrace

It’s my pleasure to welcome Matt Amdur to Delphix, to the world of DTrace, and — just today — to the blogosphere. Matt joined Delphix about two months after 10 years of software engineering, most recently at VMware. Matt and I met in at Brown University in 1997 where we worked together closely for all four years. We’ve had in the back of our minds that our professional lives would converge at some point; I couldn’t be happier to have my good friend onboard.

Matt’s first blog post is a great war story, describing his first use of DTrace on a customer system. It was vindicating to witness first hand, both in how productive an industry vet could be with DTrace after a short period, and in what a great hire Matt was for Delphix. Working with him has been evocative of our collaboration in college — while making all the more apparent the significant distance we’ve both come. Welcome, Matt!

After writing about Oracle’s port of DTrace to OEL, I wanted to take it for a spin. Following the directions that Wim Coekaerts spelled out, I installed and configured a VM to run OEL with Oracle’s nascent DTrace port. Setting up the system was relatively painless.

Here’s my first DTrace invocation on OEL:

[root@screven ~]# uname -a
Linux screven 2.6.32-201.0.4.el6uek.x86_64 #1 SMP Tue Oct 4 16:47:00 EDT 2011 x86_64 x86_64 x86_64 GNU/Linux
[root@screven ~]# dtrace -n 'BEGIN{ trace("howdy from linux"); }'
dtrace: description 'BEGIN' matched 1 probe
CPU     ID                    FUNCTION:NAME
0      1                           :BEGIN   howdy from linux
^C

Then I wanted to see what was on the system:

[root@screven ~]# dtrace -l | wc -l
574
Are you kidding me? For comparison, my Mac has 154,918 probe available and our illumos-derived Delphix OS has 77,320 (Mac OS X has many probes pre-created for each process). It looks like this beta only has the syscall provider, but digging around I can see that Wim didn’t mention that the profile provider is also there:
[root@screven ~]# modprobe profile
[root@screven ~]# dtrace -l | wc -l
587
Sweet.
[root@screven ~]# dtrace -n profile:::profile-997
dtrace: failed to enable 'profile:::profile-997': Failed to enable probe
Not that sweet.
At least I can run my favorite DTrace script:
[root@screven ~]# dtrace -n syscall:::entry'{ @[execname] = count(); }'
dtrace: description 'syscall:::entry' matched 285 probes
^C
pickup                                                            9
abrtd                                                            11
qmgr                                                             17
rsyslogd                                                         25
rs:main Q:Reg                                                    35
master                                                           52
tty                                                              60
dircolors                                                        80
hostname                                                         92
tput                                                             92
id                                                              198
unix_chkpwd                                                     550
auditd                                                          599
dtrace                                                          760
bash                                                           1515
sshd                                                           8327
I wanted to trace activity when I connected to the system using ssh… but ssh logins fail with all probes enabled. To repeat: ssh logins fail with DTrace probes enabled. I’d try to debug it, but I’m too dejected.

Evaluation

While I’d like to give this obviously nascent port the benefit of the doubt, its current state is frankly embarrassing. It’s very clear now why Oracle wasn’t demonstrating this at OpenWorld last week: it doesn’t stand up to the mildest level of scrutiny. It’s fine that Oracle has embarked on a port of DTrace to the so-called unbreakable kernel, but this is months away from being usable. Announcing a product of this low quality and value calls into question Oracle’s credibility as a technology provider. Further, this was entirely avoidable; there were other DTrace ports to Linux that Oracle could have used as a starting point to produce something much closer to functional.

This is not DTrace

So, OEL users, know that this is not DTrace. This is no better than one of the DTrace knockoffs and in many ways much worse. What Oracle released is worse than worthless by violating perhaps the most fundamental tenet of DTrace: don’t damage the system. And, to the OEL folks, I’m sure you’ll get there, but how about you take down your beta until it’s ready? As it is, people might get the wrong impression about what DTrace is.

Yesterday (October 4, 2011) Oracle made the surprising announcement that they would be porting some key Solaris features, DTrace and Zones, to Oracle Enterprise Linux. As one of the original authors, the news about DTrace was particularly interesting to me, so I started digging.

I should note that this isn’t the first time I’ve written about DTrace for Linux. Back in 2005, I worked on Linux-branded Zones, Solaris containers that contained a Linux user environment. I wrote a coyly-titled blog post about examining Linux applications using DTrace. The subject was honest — we used precisely the same techniques to bring the benefits of DTrace to Linux applications — but the title wasn’t completely accurate. That wasn’t exactly “DTrace for Linux”, it was more precisely “The Linux user-land for Solaris where users can reap the benefits of DTrace”; I chose the snappier title.

I also wrote about DTrace knockoffs in 2007 to examine the Linux counter-effort. While the project is still in development, it hasn’t achieved the functionality or traction of DTrace. Suggesting that Linux was inferior brought out the usual NIH reactions which led me to write a subsequent blog post about a theoretical port of DTrace to Linux. While a year later Paul Fox started exactly such a port, my assumption at the time was that the primary copyright holder of DTrace wouldn’t be the one porting DTrace to Linux. Now that Oracle is claiming a port, the calculus may change a bit.

What is Oracle doing?

Even among Oracle employees, there’s uncertainty about what was announced. Ed Screven gave us just a couple of bullet points in his keynote; Sergio Leunissen, the product manager for OEL, didn’t have further details in his OpenWorld talk beyond it being a beta of limited functionality; and the entire Solaris team seemed completely taken by surprise.

What is in the port?

Leunissen stated that only the kernel components of DTrace are part of the port. It’s unclear whether that means just fbt or includes sdt and the related providers. It sounds certain, though, that it won’t pass the DTrace test suite which is the deciding criterion between a DTrace port and some sort of work in progress.

What is the license?

While I abhor GPL v. CDDL discussions, this is a pretty interesting case. According to the release manager for OEL, some small kernel components and header files will be dual-licensed while the bulk of DTrace — the kernel modules, libraries, and commands — will use the CDDL as they had under (the now defunct) OpenSolaris (and to the consernation of Linux die-hards I’m sure). Oracle already faces an interesting conundum with their CDDL-licensed files: they can’t take the fixes that others have made to, for example, ZFS without needing to release their own fixes. The DTrace port to Linux is interesting in that Oracle apparently thinks that the CDDL license will make DTrace too toxic for other Linux vendors to touch.

Conclusion

Regardless of how Oracle brings DTrace to Linux, it will be good for DTrace and good for its users — and perhaps best of all for the author of the DTrace book. I’m cautiously optimistic about what this means for the DTrace development community if Oracle does, in fact, release DTrace under the CDDL. While this won’t mean much for the broader Linux community, we in the illumos community will happily accept anything of value Oracle adds. The Solaris lover in me was worried when it appeared that OEL was raiding the Solaris pantry, but if this is Oracle’s model for porting, then I — and the entire illumos community I’m sure — hope that more and more of Solaris is open sourced under the aegis of OEL differentiation.

10/10/2011 follow-up post, Oracle’s port: this is not DTrace.

At 4:08pm today, we will launch Delphix Server at DEMO. At the presentation, Richard Rothschild from TiVo will describe how they have been using Delphix. TiVo, of course, has been canonized as technology that changes the way we live or work. My past work on DTrace was described by users as “TiVo for the kernel” — a revolutionary technology from which there is no going back. The comment that “Delphix is like TiVo for databases” is all the more profound coming from the Senior Director of IT at TiVo.

I was introduced to the notion of virtualization in 2000 when some of my classmates signed on at VMware. Later in my work at Fishworks building storage products, storage virtualization was an important topic. Virtualization of both servers and storage decouples the work that’s being done, the computation or I/O and data persistence, from specific, inflexible physical resources. Those physical resources can then be used more efficiently (saving money) and moved around more quickly and easily (saving time).

Databases, while not themselves physical resources, are bound to physical resources in an analogous way. They are tied to equipment, duplicated many times over, and complex to provision and deploy — much like both servers and storage. Delphix brings virtualization to the realm of databases, abstracting them away from their physical resources, and creating the same benefits as virtualizing compute or disk. In contrast though, since databases are not tangible like a rack-mount server or storage array, databases can be seamlessly pulled into the virtualization framework, or, just as easily, recast and deployed as physical databases.

Check out the broadcast live today (or here after the fact), or take a look at today’s eWeek article. We’ve also got some videos posted with more info on the product and customer testimonials. As I write this, I’m midway through my second day at the company; I look forward to writing more about the technology as I dive in.

I joined the Solaris Kernel Group in 2001 at what turned out to be a remarkable place and time for the industry. More by luck and intuition than by premonition, I found myself surrounded by superlative engineers working on revolutionary technologies that were the products of their own experience and imagination rather than managerial fiat. I feel very lucky to have worked with Bryan and Mike on DTrace; it was amazing that just down the hall our colleagues reinvented the operating system with Zones, ZFS, FMA, SMF and other innovations.

With Solaris 10 behind us, lauded by customers and pundits, I was looking for that next remarkable place and time, and found it with Fishworks. The core dozen or so are some of the finest engineers I could hope to work with, but there were so many who contributed to the success of the 7000 series. From the executives who enabled our fledgling skunkworks in its nascent days, to our Solaris colleagues building fundamental technologies like ZFS, COMSTAR, SMF, networking, I/O, and IPS, and the OpenStorage team who toiled to bring a product to market, educating us without deflating our optimism in the process.

I would not trade the last 9 years for anything. There are many engineers who never experience a single such confluence of talent, organizational will, and success; I’m grateful to my colleagues and to Sun for those two opportunities. Now I’m off to look for my next remarkable place and time beyond the walls of Oracle. My last day will be August 20th, 2010.

Thank you to the many readers of this blog. After six years and 130 posts I’d never think of giving it up. You’ll be able to find my new blog at dtrace.org/blogs/ahl (comments to this post are open there); I can’t wait to begin chronicling my next endeavors. You can reach me by email here: my initials at alumni dot brown dot edu. I look forward to your continued to comments and emails. Thanks again!

I’ve been expecting this automated mail for a while now, but it was disheartening nonetheless:

List:       dtrace-discuss
Member:     bryan.cantrill@eng.sun.com
Action:     Subscription disabled.
Reason:     Excessive or fatal bounces.
Bryan Cantrill, VP of Engineering at Joyent, earning $15.

As one of the moderators of the DTrace discussion list, I see people subscribe and unsubscribe. Bryan has, of course, left Oracle and joined Joyent to be their VP of engineering.

Bryan is a terrific engineer, and I count myself lucky to have worked with him for the past nine years first on DTrace and then on Fishworks. He taught me many things, but perhaps most important was his holistic view of engineering that encompasses all aspects of making a product successful including docs, pricing, talks, papers, and, of course, excellent code. Now Bryan is off to cut through the layers software that make up the cloud. Far from leaving the DTrace community, he’s going to take DTrace to new places and I look forward to seeing the fruits of his labor as he sinks his teeth into a new onion of abstractions.

… and, Robin, Bryan’s certainly a smart guy, but “the smart guy behind Dtrace [sic]”?? Just don’t refer to me and Mike as “the dumb guys behind DTrace” okay?

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