I have a new blog post up at the Intel Developer Zone, this time about the Simics “fulprompt”. Every software team has its legends about spectacular mistakes, crazy users, and customer calls with strange questions. The Simics “fulprompt” is one example of this from the early days of Simics. It was a prompt that appeared where no prompt would normally appear, right in the middle of executing an instruction. As such, it was an ugly hack… and for Swedes who were around in the 1990s, the only name for a ugly hack is a fulhack.
Injecting faults into systems and subjecting them to extreme situations at or beyond their nominal operating conditions is an important part of making sure they keep working even when things go bad. It was realized very early in the history of Simics (and the same observation had been made by other virtual platform and simulator providers) that using a virtual platform makes it much easier to provide cheap, reliable, and repeatable fault injection for software testing. In an Intel Developer Zone (IDZ) blog post, I describe some early cases of fault injection with Simics.
Back in 2004, the startup Virtutech built a crazy demo for the 2004 Embedded Systems Conference (ESC). Back then, ESC was the place to be, and Virtutech was there with a battery of demos to blast the competition. The most interesting demo from a technology perspective was the 1002-machine network, as described in an Intel Developer Zone blog post of mine.
I have just released a new blog post on my Intel Developer Zone blog, about how Simics runs
large huge workloads. I look back at the kinds of workloads that ran on Simics back in 1998 when the product first went commercial, and then look at some current examples running on Simics. This is the first post in a series intended to celebrate 20 years of Simics as a commercial product.
I will be presenting an Exhibitor Forum talk at the Embedded World in Nürnberg next week, about how to get to Agile and small batches for embedded. Using simulation to get around the annoying hard aspect of hardware.
There is a blog post out on my Intel Developer Zone blog where I take a look at the Gartner “Top Ten Tech Trends” for 2018. There are a couple of them where I found clear roles for the kinds of simulation tools we build in my little corner of Intel. In particular, Digital Twins is a concept that is all about simulation. To find the other trend where I found a big role for simulation, read the full blog post.
A while ago, I visited my Intel colleagues in Costa Rica and ran a workshop for university teachers and researchers, showing how Simics could be used in academia. I worked with a very smart and talented intern, Jose Fernando Molina, and after a rather long process I have published an interview with him on my Intel blog: https://software.intel.com/en-us/blogs/2017/12/05/windriver-simics-to-inspire-teachers-costarica
Over time, Intel and other processor core designers add more and more instructions to the cores in our machines. A good question is how quickly and easily new instructions added to an Instruction-Set Architecture (ISA) actually gets employed by software to improve performance and add new capabilities. Considering that our operating systems and programs are generally backwards-compatible, and run on all kind of hardware, can they actually take advantage of new instructions?
I have posted a two-part blog post to the public Intel Developer Zone blog, about the “Small Batches Principle” and how simulation helps us achieve it for complicated hardware-software systems. I found the idea of the “small batch” a very good way to frame my thinking about what it is that simulation really brings to system development. The key idea I want to get at is this:
[…] the small batches principle: it is better to do work in small batches than big leaps. Small batches permit us to deliver results faster, with higher quality and less stress.
Integration is hard, that is well-known. For computer chip and system-on-chip design, integration has to be done pre-silicon in order to find integration issues early so that designs can be updated without expensive silicon re-spins. Such integration involves a lot of pieces and many cross-connections, and in order to do integration pre-silicon, we need a virtual platform.
Doing continuous integration and continuous delivery for embedded systems is not necessarily all that easy. You need to get tools in place to support automatic testing, and free yourself from unneeded hardware dependencies. Based on an inspiring talk by Mike Long from Norway, I have a piece on how simulation helps with embedded CI and CD on my Software Evangelist blog on the Intel Developer Zone.
Simics and other simulation solutions are a great way to add more variation to your software testing. I have just documented a nice case of this on my blog at the Intel Developer Zone (IDZ), where the Simics team found a bug in how Xen deals with MPX instructions when using VT-x. Thanks to running on Simics, where scenarios not available in current hardware are easy to set up.
Last year (2015), a paper called “Don’t Panic: Reverse Debugging of Kernel Drivers” was presented at the ESEC/FSE (European Software Engineering Conference and the ACM SIGSOFT Symposium on the Foundations of Software Engineering) conference. The paper was written by Pavel Dovgalyuk, Denis Dmitriev, and Vladimir Makarov from the Russian Academy of Sciences. It describes a rather interesting approach to Linux kernel device driver debug, using a deterministic variant of Qemu along with record/replay of hardware interactions. I think this is the first published instance of using reverse debugging in a simulator together with real hardware.
I am going to present a paper about our new SystemC Library in Simics, at the DVCon Europe conference taking place in München next month. The paper is titled “Integrating Different Types of Models into a Complete Virtual System – The Simics SystemC* Library”, and I authored it together with my Intel colleagues Andreas Hedström, Xiuliang Wang, and Håkan Zeffer.
My first blog post as a software evangelist at Intel was published last week. In it, I tell the story of how our development teams used Simics to test the software behavior (UEFI, in particular) when a server is configured with several terabytes of RAM. Without having said server in physical form – just as a simulation. And running that simulation on a small host with just 256 GB of RAM. I.e., the host RAM is just a small fraction of the target. That’s the kind of things that you can do with Simics – the framework has a lot of smarts in it.
It was rather interesting to realize that just the OS page tables for this kind of system occupies gigabytes of RAM… but that just underscores just how gigantic six terabytes of memory really is.
This really happened last week, but I was in the US for the DAC then. I did another blog on Intel Software blog, about a white paper that Wind River put out about how they use Simics internally. The white paper is a really good set of examples of how Simics can be used for software development, test, and debug – regardless of how old or new the hardware is. It also touches my favorite topic of IoT simulation and scaling up – Wind River is actually using Simics for 1000+ node tests of IoT software! Read on at https://blogs.intel.com/evangelists/2016/06/06/wind-river-uses-simics-test-massive-iot-networks/
I love bug and debug stories in general. Bugs are a fun and interesting part of software engineering, programming, and systems development. Stories that involve running Simics on Simics to find bugs are a particular category that is fascinating, as it shows how to apply serious software technology to solve problems related to said serious software technology. On the Intel Software and Services blog, I just posted a story about just that: debugging a Linux kernel bug provoked by Simics, by running Simics on a small network of machines inside of Simics. See https://blogs.intel.com/evangelists/2016/05/30/finding-kernel-1-2-3-bug-running-wind-river-simics-simics/ for the full story.
There are still some articles being published that I wrote while at Wind River. The latest is a piece on just what you could do with a lab in cloud – in particular, a lab based on virtual platforms like Simics. Eva Skoglund at Wind River and I wrote this together, and it is a nice high-level summary of why you really need to have a virtual cloud-based lab if you are doing embedded systems development. It is published in the online European magazine Electropages.
A new record, replay, and reverse debugger has appeared, and I just had to take a look at what they do and how they do it. “rr” has been developed by the Firefox developers at Mozilla Corporation, initially for the purpose of debugging Firefox itself. Starting at a debugger from the angle of attacking a particular program does let you get things going quickly, but the resulting tool is clearly generally useful, at least for Linux user-land programs on x86. Since I have tried to keep up with the developments in this field, a write-up seems to be called for.
Intel is a big Simics user, but most of the time Intel internal use of Simics is kept internal. However, we recently had the chance to interview Karthik Kumar and Thomas Willhalm of Intel about how they used Simics to interact with external companies and improve Intel hardware designs. The interview is found on the Wind River blog network.
It is also my last blog post written at Wind River; since January 18, I am working at Intel. I am working on ways to keep publishing texts about Simics and simulation, but the details are not yet clear.
I just posted a short blog post on the Wind River blog, introducing a video demo of the Web API to Wind River Helix Lab Cloud. In the post and video, I show how the Lab Cloud Web API works. For someone familiar with REST-style APIs, this is probably baby-level, but for me and probably most of our user base, it is something new and a rather interesting style for an API. Thus, doing a video that shows the first few steps of authentication and getting things going seems like a good idea.
In a blog post at Wind River, I describe how the Wind River Helix Lab Cloud system can be used to communicate hardware design to software developers. The idea is that you upload a virtual platform to the cloud-based system, and then share it to the software developers. In this way, there is no need to install or build a virtual platform locally, and the sender has perfect control over access and updates. It is a realization of the hardware communication principles I presented in an earlier blog post on use cases for Lab Cloud.
But the past part is that the targets I talk about in the blog post and use in the video are available for anyone! Just register on Lab Cloud, and you can try your own threaded software and check how it scales on a simulated 8-core ARM!
On November 3, 2015, I will give a presentation at the Embedded Conference Scandinavia about simulating IoT systems. The conference program can be found at http://www.svenskelektronik.se/ECS/ECS15/Program.html, with my session detailed at http://www.svenskelektronik.se/ECS/ECS15/Program/IoT%20Development.html.
My topic is how to realistically simulate very large IoT networks for software testing and system development. This is a fun field where I have spent significant time recently. Only a couple of weeks ago, I tried my hand simulating a 1000-node network. Which worked! I had 1000 ARM-based nodes running VxWorks running at the same time, inside a single Simics process, and at speeds close to real time! It did use some 55GB of RAM, which I think is a personal record for largest use of system resources from a single process. Still, it only took a dozen processors to do it.
There is a new post at my Wind River blog, about the new Wind River Helix Lab Cloud product that we launched for real last week. The Lab Cloud is a really cool way to expose Simics-style functionality, and my blog goes through some of the more prominent use cases for a simulator in the cloud. There a couple of demo videos linked from the blog, and I have also set up a Youtube playlist collecting the Simics demos and other videos that we have posted there. Quite a set over the past few years, actually!
There is a new post at my Wind River blog, about how I helped a colleague resolve a real problem using the preview version of the new Helix Lab Cloud system. The Lab Cloud right now is basically Simics behind a simplified web user interface, exposing the checkpointing and record-replay facilities in a very clear way. You can also share your sessions for live interactions with other people, which is truly cool.
I just added a new blog post on the Wind River blog, about how you do fault injection with Simics. This blog post covers the new fault injection framework we added in Simics 5, and the interesting things you can do when you add record and replay capabilities to spontaneous interactive work with Simics. There is also a Youtube demo video of the system in action.
On June 30, Wind River (my job) released Simics 5, the latest version of Simics. I have been working with Simics since 2002 now, and the tool is still improving, adding new features, and adopting the current world. The announcement blog post provides an overview of the features of the new release, and we will be doing some additional in-depth posts later on.
While I was on vacation, Wind River published a blog post I wrote about the new multicore accelerator feature of Simics 5. The post has some details on what we did, and some of the things we learnt about simulation performance.
There is a new post at my Wind River blog, about the Simics Agent feature that we included in Simics last year. Took a while to get a blog out, as I had so many other things to write about. It was also nice to get a video demo out to accompany the post. The most interesting part about the Simics Agent to me is how much more convenient it is to script a target with an agent on the inside. Too bad that also changes the target software stack a bit — but I do think that that is OK most of the time. As always, the solution has to be designed with the end goal in mind, and there is no absolute right or wrong here. Read the blog post for more details!
There is a new post at my Wind River blog, about the Trinity of Simulation – the computer, the system, and the world. It discusses how you build a really complete system model using not just a virtual platform like Simics, but you also integrate it with a model of the system the computer sits in, as well as the world around it. Like this:
Read more about it in the blog post, and all the older blog posts it links to!