Archive for November, 2007|Monthly archive page

Software ports galore!

A couple of weeks ago I wrote about the port of dtrace that Colin and I have got up and running under Neutrino.   For the most part, porting software to Neutrino is a pretty straightforward matter.  Since Neutrino runs self-hosted (ie you work and build in the same environment that you deploy) it means that all of the ‘configure/make’ style projects work without too much hassle.  In fact most of the time if the source is coming from Linux, *BSD, Solaris or some other unix flavour you can get it up and running in a couple of hours.  The main challenge is almost always figuring out the build system and making sure that our compiler front end (qcc) is used to pick up all of the required environment bits and that hacks for other systems are really required for Neutrino (which is pretty well behaved).

Having ported software on a self-hosted system is pretty much essential for a software developer to work effectively.  There are so many essential software bits and pieces that QNX would never include with the Neutrino SDK because while they are useful, the SDK is targeted specifically at what is needed to build Neutrino applications and needs to be portable (and consistent) for use under Windows, Linux, Solaris as well as Neutrino self-hosted x86.   That doesn’t mean that the extra software bits aren’t useful, and historically a 3rd party CD was provided for Neutrino self-hosted developers that came with loads of useful extras, from scripting languages (perl, python, tk) to web servers (apache) and editors (vim).

A couple of developers here at QNX, Sean B. and Xiaodan T., with the help of some QNX community members have been working on a wicked awesome project that pretty much replaces the 3rd party CD with something even better!  They have been working to port the BSD pkgsrc tool/project to support the QNX Neutrino self-hosted environment.   Just the other day I got a message in my mailbox indicating that the project had hit a critical milestone and that QNX Neutrino was now considered a full fledged supported platform:

“we are proud to welcome QNX, thanks to Sean Boudreaux.”

It is even listed on the projects main documentation page … now that is super cool news!  There are 7000+ different software packages part of this collection, and to have all of them available pre-ported and on-demand is a pretty awesome feat.

So if you are running Neutrino self-hosted, (and why wouldn’t you be!) and you want more than just the stock installed software, then you should definitely take a look at the pkgsrc community project

Congratulations and thanks to Sean, Xiaodan and all the others who’ve been working on getting this up and running!



Mutex madness?

I recently received an interesting kernel trace from a customer. It showed several threads going from STATE_RUNNING to STATE_MUTEX without an intervening SyncMutexLock kernel call. He wondered if perhaps the trace was corrupted.

After looking at the trace it seemed to be sane, but the behaviour shown was somewhat puzzling. However it is explainable, and it has to do with our implementation of mutexes.

Continue reading

I trace, you trace … what about dtrace?

Anyone who has been plugged into the OS scene is surely aware of the latest Mac OS X Leopardrelease.  It is hard to miss since the news is pretty much splashing up all over the place in news articles and product reviews and in my case filling my mailbox with Google Alerts.  I don’t have an alert set for Max OS X, but I do have one set for DTrace and this tracing functionality has now been included in the latest Mac OS X release and people seem to be pretty jazzed about it.

I’m jazzed about it too … but for a different reason all together. 

Colin and I have been following the work of Bryan, Mike and Adamon dtrace since it was released as part of the Open Solaris.  We head up most of the kernel instrumentation and system profilingdevelopment on Neutrino and have always felt that dtrace, with its focus on runtime safety and use in a production environment, would be a perfect match for embedded developers and compliment our existing instrumentation and tracing strategy for Neutrino very nicely.  

So why were we jazzed by the Max OS X release? The more platforms that dtrace is ported to, the more generic the code base will become.  It is exciting to us because now dtrace is running on Solaris, NetBSD, Max OS X and oh yeah … Neutrino!

dtrace on Neutrino

You can see here that this is a system that is running the 6.3.0 release of Neutrino and this is the basic dtrace command help.  The initial port to Neutrino that Colin and I have done is slightly different from the other OS ports.  Since Neutrino is an micro-kernel, we wanted to see how far we could go keeping the dtrace module out  of the kernel … and if possible even outside of the process manager.  The current implementation has all of the dtrace system code, normally found in the kernel or a kernel module, encapsulated in a resource manager, io-dtrace, and the utility is a straight port of the Solaris utility.

dtrace provider listing

We’ve only implemented three sets of providers currently. 

  • dtrace:  This is the standard dtrace provider with the BEGIN, END and ERROR probes
  • instr: This is a provider based on the existing kernel instrumentation hook and can provide kernel calls, thread state, interrupt information
  • profile: This provider is pretty much the same as the Solaris provider and provides statistical sampling at a user controlled rate

Even with this minimal set of providers, you can extract some pretty interesting information.  For example, we can re-write the hogs utility, that tracks the runtime of the top few processes, with a simple dtrace script:

HOGS dtrace script

We are missing a lot of the standard dtrace built-ins that allow you to get much deeper into the application space, such as providing the user stack information, but even by recording the instruction pointer we can get some usefull information about where an application is spending its time … expanding on the idea of an application specific statistical profiler, we can gather information about the whole system or target just one process or thread:

Mapping the IP address

Since dtrace can work directly with C constructs, we can pull in code directly from the Neutrino system headers.  If you wanted to take a look at the kind of messaging operations that were going on in a process, you could write a script to catch all of the MsgSend’s via the instrumentation hook and decode the first few bytes of data based on the message header to determine what an application is doing:

Decoding the message

Pretty cool huh! It is a nice extension to the capabilities of the System Profiler that provides the graphical analysis capabilities, but in a development environment back on the host.

There is still have a lot to do and the port is far from complete.  Before we can go much further, we are likely going to have to do the kernel and/or process manager integration to be able to efficiently provide things like the equivalent of the pid provider and the function boundary tracing.  The good news is that as a proof of concept this is already usefull … and so far architecturally independent (running on MIPS, SH, ARM, PPC and of course x86), although the hard bits are still ahead of us. 

Hats off to Bryan, Mike and Adam for a wicked awesome technology and to Sun to making it available to the software development community.  Since the port isn’t quite complete, certainly not production ready, Colin and I are hoping that we can get our prototype posted up to the Foundry27 QNX community site so that we aren’t the only ones who get a chance to play around with this. 

Stay tuned …

Thomas (& Colin who is onsite with a customer … likely using the dtrace prototype right now)