Computer simulation, programming, software, technology, research, and more (since 2007)
There is a new post at my Wind River blog, about how I ran a Windows file share server (CIFS) on a Simics-simulated VxWorks big-endian Power Architecture target. Something that just should work, given that the software in question is known to work in the real world. But still, pretty cool, and a bit eerie.
On my Wind River blog, you can now find a description on how we have used the Eclipse TCF (target connection framework) to build the Simics GUI. Or rather, the connection between the Simics GUI and the Simics simulation process. It is actually quite revolutionary what you can do with the TCF, compared to older debug protocols. In particular, TCF lets you combine many different services across a single connection.
Last year, I did a Simics webinar which included a two-part demo of how to use Simics to debug an endianness bug in a networked system as it migrates from big-endian to a little-endian system. Along the way, I also showed off various Simics features like reverse execution and checkpointing and scripted execution.
The demo is now online at the Wind River Youtube channel, and the setup is explained in a blog post at the Wind River company blog which is worth reading before watching the video.
I just added a new blog post at the Wind River blog, about determinism and illustrating Simics-style determinism is by looking at the game Bad Piggies. Games and simulators have quite a lot in common, actually.
Continue reading “Wind River Blog: Simics and Flying Piggies”
There is a new blog post on my Wind River blog, about the Landslide system from CMU. It is a pretty impressive Master’s Thesis project that used the control that Simics has over interrupts to systematically try different OS kernel thread interleavings to find concurrency bugs. The blog is an interview with Ben Blum, the student who did the work. Ben is now a PhD student, and I bet that he will continue to generate cool stuff in the future.
A few years ago, I built a demo on Simics that used a hacked Freescale MPC8641D target that was forced to scale from 1 to 8 cores. Some interesting experiements could be made using this target, and it was nicely scalable for its time. However, I always wanted to have something just a bit bigger. Say 20 cores, or 100. Just to see what would happen. Finally, I got it.
The Simics QSP target that we quietly launched earlier this Summer is such a scalable target. As discussed in a blog post describing the architecture, it is designed to scale to 128 cores currently. Using this ability, I repeated my old experiments, but trying very large threads counts and target core counts. The results show clearly that the way that I coded my parallel computation program was pretty bad, and I really would like to try to rewrite it using some more modern threading library. All I need is time and a way to cross-compile Wool…
Anyway, the new blog post is here.
There is a new post at my Wind River blog, about the design and technical contents of the new Simics Quick Start Platforms, more widely known as the QSP. The blog describes the virtual-only hardware that forms part of the QSP, and how it was designed. It is interesting to note that the hardware ended up a bit more complex that I initially thought it would be, since an ideal virtual platform should be very simple. Right? Turns out an OS complicates things.
Continue reading “Wind River Blog: Inside the Simics QSP – Additional Notes”
On the Wind River corporate blog, I have put up a blog post about how Wind River Education Services is going to use Simics to teach networking. What is interesting with this approach is that it shows how a virtual platform can be used for tasks like teaching that don’t have much to do with hardware modeling or similar “typical” VP uses. In this case, the key value is encapsulation of a set of machines running real operating systems and software stacks, and with lots of networks connecting them.
There is a new post at my Wind River blog, about how a team of researchers at the University of Nebraska at Lincoln is using Simics to force rare bugs to manifest themselves as errors. They used Simics to control a target system to force it into rare situations much more likely to trigger latent bugs, requiring far fewer test runs compared to just randomly rerunning tests again and again and hoping to see a bug.
There is a new post at my Wind River blog, about how the LDRA code coverage tools have been brought to work on Simics using a simulation-only “back door “.
The most interesting part of this is how a simulator can provide an easy way to get information out of target software, without all the software and driver overhead associated with doing the same on a real target. In this case, all that is needed is a single memory-mapped location that can written to be software – which can be put into user-mode-accessible locations if necessary.
Continue reading “Wind River Blog: Code Coverage over a Back Door”
Wind River recently added a couple of new processor models to Simics: the 30-year-old 80186 and the 32-year-old 8051.
I have a blog post about this up on the Wind River tools blog. Pretty amazing to see us model an eight bit machine in 2012 – just proves how long-lived some hardware systems are.
There is a new post at my Wind River blog, about Simics running a model of the new Intel Crystal Forest platform. Crystal Forest is a very complex piece of hardware, but I am pretty happy that we managed to demo it in an understandable way – by essentially using it as a black box and putting a pretty display on top of that (using Eclipse).
There is a new post at my Wind River blog, about how you actually do fault injection in Simics. This particular post is pretty detailed, showing the actual architecture of a fault injector in Simics, not just “yes you can do it”. It includes actual diagrams of system components and how you can insert fault injection into an existing system, so it is a bit more technical than most my Wind River blog posts that tend to be more conceptual.
There is a new post at my Wind River blog, an interview with Dan Poirot at RTI who is using Simics to model and test heterogeneous, distributed, networked systems.
On my Wind River blog, I just posted a fairly long post about simulation abstraction levels. It was inspired by a cool article in ArsTechnica about Nintendo emulators, and the costs and benefits of being ever more faithful to the hardware.
There is a new post at my Wind River blog, which could seem to be about shoes but which is really about process improvement. In particular, the need for companies to let their employees take a step or two back and look at what they are doing and what they could do better.
It is way too common to be so busy running around being inefficient that there is no time to think about how to become more efficient. Change also requires some discipline to actually keep pushing at habits until they change for the better.
Just for fun, I tried to surf the web of today using a Netscape 4 browser from 2001.
The result: not exactly useful. Netscape 4 was bad back then, and it does not work at all with the current style of web coding.
There is a new post at my Wind River blog, about hypersimulation in virtual platforms and how it lets virtual time fly much faster than real time. It was the result of simple mistake of leaving Simics running in the background as I did other work on my machine.
There is a new post at my Wind River blog, about how you build virtual platforms with Simics. The post is more about the methodology than the nature of models, cycle accuracy, endianness, and all the other details of virtual platform modeling. I have written about modeling methodology on this blog too, and in particular I would recommend looking at “Two perspectives on modeling“.
There is a new post at my Wind River blog, about the “Toddler stage” of software in general and Simics 4.6 in particular. To me, software in an early stage of development shares many traits with a toddler:
The software will sometimes behave as expected, but more often than not it will not. It will do something else, or crash, or generally do the wrong thing. It is very much like a toddler – you can rely on it to some extent, but you never know when it will decide to do something unexpected, funny, or just throw a fit over something that would have seemed inconsequential.
There is a new post at my Wind River blog, about the new Simics 4.6 release. 4.6 has some serious new goodies in it, including an Eclipse source-code debugger and a way to build blinking lights front panels for boards.
There is a new post at my Wind River blog, about some computing history. Wind River turns thirty this year, Simics twenty, and simulation for debug (and probably debug in general) turns sixty. Computing has come a long way.
There is a new post at my Wind River blog, about how Simics was used to kick-start the development of the 64-bit version of VxWorks. It is an interesting example of how to use a virtual platform as a model of something much simpler and gentler than actual hardware systems.
There is a new post at my Wind River blog, about the testing on an integrated software stack in simulation. I base the discussion on the very interesting report about the Toyota “unintended acceleration” problems and the deep investigation into the control software of the affected vehicles performed by a NASA team (!). The report covers a lot of different tools, but also notes that about the only thing not done was to integrate the complete software stack in simulation.
There is a new post at my Wind River blog, about how you can use a virtual platform to complete work faster. Not by making the virtual platform execution of target code faster, but by optimizing the way you work and taking advantage of the features of a virtual platform.
There is a new post at my Wind River blog, about how you can use a virtual platform to complete work faster. Not by making the virtual platform execution of target code faster, but by optimizing the way you work and taking advantage of the features of a virtual platform.
There is a new post at my Wind River blog, about warnings in virtual platforms. It is an art to add good warnings to virtual platform models, and just being correct visavi the hardware behavior is not necessarily that helpful for a software developer. A virtual platform should warn about suspicious operations, even if they … Continue reading “Wind River Blog: Being Helpful or Being Correct?”
There is a new post at my Wind River blog, about warnings in virtual platforms. It is an art to add good warnings to virtual platform models, and just being correct visavi the hardware behavior is not necessarily that helpful for a software developer. A virtual platform should warn about suspicious operations, even if they are technically “correct”.
I also have to apologize for the slow blogging in January of 2011. There was too much going on at work and quite a few days taking care of sick kids. Hopefully, the pace can improve going forward.
There is a new post at my Wind River blog, about iterative hardware-software interface design. It is a discussion with some examples of why hardware designers would do well to use virtual platforms to include software designers in the loop when designing new devices and their programming interfaces.
There is a new post at my Wind River blog, about iterative hardware-software interface design. It is a discussion with some examples of why hardware designers would do well to use virtual platforms to include software designers in the loop when designing new devices and their programming interfaces.
New post up at my Wind River blog, about cheating in virtual platforms.
I have a fairly lengthy new blog post at my Wind River blog. This time, I interview Tennessee Carmel-Veilleux, a Canadian MSc student who have done some very smart things with Simics. His research is in IMA, Integrated Modular Avionics, and how to make that work on multicore.
Last week, I posted a discussion about fault injection in virtual systems, using Basil Fawlty as the perfect example of a fault injection agent.