Developing Applications for LE (little endian)

Body

by Jeff Scheel, IBM Linux on Power Chief Engineer

In June of last year, I started publicly discussing the role that little endian (LE) plays in our Linux on Power strategy with the blog, Just the FAQs about Little Endian. Then, in August I attempted to eliminate uncertainty in my Removing the FUD and Demystifying LE (little endian) article. With the announcement of the Red Hat Enterprise Linux 7.1 beta delivering an LE version, it is time to revisit little endian from the perspective of an application developer.

The release of RHEL 7.1 LE completes the offerings of little endian operating systems. Canonical had Ubuntu 14.04 ready for POWER8 launch in May. SUSE supported the launch with public statements by Michael Miller about SLES 12 being LE in May, and publicly released in October. It is now time for application developers to get busy: little endian Linux on Power is here!

One thing that being a developer by training has taught me, is that “we” often need to be convinced that work is worth doing. Little endian Linux on Power is about reducing the cost of migrating an application AND providing additional value of the end application.

Being able to run Linux on Power in LE mode means that applications have one less thing – data endianness – to worry about in the port. While technical differences such as assembler language, page size, and cache size still exist, developers and architects tend to worry most about data endianness because the finding and fixing all the problems can be very time consuming. By enabling Power to run in the same endian mode as x86 (the defacto Linux platform of choice for developers), applications can simply be recompiled without having to worry about endianness. Further, if one is going to build a solution mixed with x86 and POWER systems, exchanging data on disk or across the network in the same endian mode greatly simplifies the application as well. Then, add in the ability to accelerate Power applications with (inherently little endian) GPUs and the benefits of little endian become “a no brainer”.

So, hopefully, we're past the “why should I do this?” phase and now we address the list of technical resources for migrating to Linux on Power. My favorite list of resources include:

1. The Linux on Power community in developerWorks has a great wiki page Porting from Intel x86 to Power systems running Linux that provides a great starting point for the process.

2. If you are migrating your application from x86 Linux and like bundles or toolkits, the Software Development Toolkit for Linux on Power provides an Eclipse-based environment for C/C++ applications with a porting wizard (The Migration Advisor) and a tuning wizard (Souce Code Analyzer) for development efficiently. This bundle further provides the latest free software (GNU) tools, oprofile, gdb and several Power-unique tools such as FDPR for post link optimization, pthread-mon to analyze highly threaded applications, and CPI (cycles per instruction) tooling to visually show inefficiencies.

3. For the best advice on tuning your application, I recommmend starting at the Performance Rocks – Best Practices wiki page in developerWorks.

4. The Performance Optimization and Tuning Techniques for IBM Processors, including IBM POWER8 Redbook provides excellent insight to the Power processor.

Now let us take a look at “where can I get started?” The answers to this question depend on your role in the software ecosystem. If you are a software provider, my colleague Bob Dick, recently published he thoughts on how to get started in a the Using the IBM Power Development Cloud for Red Hat Enterprise Linux 7.1 (little endian) Beta application testing blog posting. Programs like IBM PartnerWorld provide this and more resources to facilitate porting. Check them out.

If you are a “in house” owner of an application in your enterprise, finding a system on which to port your application could be challenging. Of course, your IBM Sales contact or your business partner can provide alternatives such as try-and-buy or proof-of-concept systems. Do not hesitate to start with them. If you do not know them, or if this does not work out, go to the cloud! Site Ox offers a two week free trial for development purposes. Visit their website for details. As we move forward, I remain hopeful that other vendors will provide public offerings of Linux on Power images. Further, if you do not at first see the particular release for which you are looking, reach out to the service provider and request it. They might just surprise you and have a plan to provide it. If not, it helps them to hear your needs.

For open source developers, the access to free cloud images increases. The Open Source Labs at Oregon State University hosts Power development images (VMs). University of Campinas (UNICAMP) also hosts a minicloud in Brazil. In China, the SuperVessel Cloud provides a similar service to developers. In addition to these three locations, we are hoping to extend our offerings in both Europe and India in the near future. Again, the particular releases hosted at these sites may vary, but will generally include the little endian versions of Fedora, openSUSE, and Debian. If none of these sites or offerings work for you, feel free to reach out to me on Google+ (loaner post) to explore a dedicated loaner system.

With a complete set of little endian Linux on Power distributions, a robust list of technical resources, and plenty of resources for porting applications, the future is here. Take the first step. Seize the moment. Let's see what you can do with Linux on Power!