_   __               __   _  __                
   / | / /____ _ __  __ / /_ (_)/ /__  __ _____    
  /  |/ // __ `// / / // __// // // / / // ___/ 
 / /|  // /_/ // /_/ // /_ / // // /_/ /(__  )     
/_/ |_/ \__,_/ \__,_/ \__//_//_/ \__,_//____/

The Nautilus AeroKernel

Nautilus is an example of an AeroKernel, a very thin kernel-layer exposed (much like a library OS, or libOS) directly to the runtime and application. AeroKernels are suited particularly well for parallel runtimes that need fine-grained, explicit control of the machine to squeeze every bit of performance out of it. Note that an AeroKernel does not, by default, have a user-mode! There are several reasons for this, simplicity and performance among the most important. Furthermore, there are no heavy-weight processes---only threads, all of which share an address space. Therefore, Nautilus is an example of a single address-space OS (SASOS). The runtime can implement user-mode features or address space isolation if this is required for its execution model.

Hybrid Runtimes (HRTs) and Hybrid Virtual Machines (HVM)

We call the combination of an AeroKernel and the runtime/application using it a Hybrid Runtime, in that it is both a runtime and a kernel, esp. regarding its ability to use the full machine and determine the proper abstractions to the raw hardware (if the runtime developer sees a mismatch with his/her needs and the AeroKernel mechanisms, they can be overridden).

If stronger isolation or more complete POSIX/Linux compatibility is required, it is useful to run the HRT in the context of a Hybrid Virtual Machine. An HVM allows a virtual machine to split the hardware resources among a regular OS (ROS) and an HRT. The HRT portion of the HVM can then be seen as a kind of software accelerator. Note that because of the simplicity of the hardware abstractions in a typical HRT, virtualization overheads are much, much less significant than in, e.g. a Linux guest.


  • gcc cross compiler (more on this to come)
  • grub version >= 2.02
  • xorriso (for CD burning)
  • QEMU recommended if you don't want to run on raw hardware

Hardware Support

Nautilus works with the following hardware:


First, configure Nautilus by running

make menuconfig

Select any options you require, then run make to build the HRT binary image. To make a bootable CD-ROM, run make isoimage. If you see weird errors, chances are there is something wrong with your GRUB2 toolchain (namely, grub-mkrescue). Make sure grub-mkrescue knows where its libraries are, especially if you've installed the latest GRUB from source. Use grub-mkrescue -d. We've run into issues with naming of the GRUB2 binaries, in which case a workaround with symlinks was sufficient.

Running and Debugging under QEMU


$> qemu-system-x86_64 -cdrom nautilus.iso -m 2048

Nautilus has multicore support, so this will also work just fine:

$> qemu-system-x86_64 -cdrom nautilus.iso -m 2048 -smp 4

You should see Nautilus boot up on all 4 cores.

Nautilus is a NUMA-aware AeroKernel. To see this in action, try (with a sufficiently new version of QEMU):

$> qemu-system-x86_64 -cdrom nautilus.iso \
                      -m 8G \
                      -numa node,nodeid=0,cpus=0-1 \
                      -numa node,nodeid=1,cpus=2-3 \
                      -smp 4,sockets=2,cores=2,threads=1

Nautilus supports debugging over the serial port. This is useful if you want to debug a physical machine remotely. All prints after the serial port has been initialized will be redirected to COM1. To use this, find the SERIAL_REDIRECT entry and enable it in make menuconfig. You can now run like this:

$> qemu-system-x86_64 -cdrom nautilus.iso -m 2G -serial stdio

Running and Debugging under BOCHS

While we recommend using QEMU, sometimes it is nice to use the native debugging support in BOCHS. We've used BOCHS successfully with version 2.6.8. You must have a version of BOCHS that is built with x86_64 support, which does not seem to be the default in a lot of package repos. We had to build it manually. You probably also want to enable the native debugger.

Here is a BOCHS config file (~/.bochsrc) that we used successfully:

ata0-master: type=cdrom, path=nautilus.iso, status=inserted
boot: cdrom
com1: enabled=1, mode=file, dev=serial.out
cpu: count=2
cpuid: level=6, mmx=1, level=6, x86_64=1, 1g_pages=1
megs: 2048


You can find publications related to Nautilus and HRTs/HVMs at http://halek.co

Our lab: www.presciencelab.org


Nautilus was made possible by support from the United States National Science Foundation (NSF) via grant CNS-0709168, the Department of Energy (DOE) via grant DE-SC0005343, and Sandia National Laboratories through the Hobbes Project, which is funded by the 2013 Exascale Operating and Runtime Systems Program under the Office of Advanced Scientific Computing Research in the DOE Office of Science. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

Kyle C. Hale (c) 2015 Northwestern University