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Akaros Operating System
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brho vmm: refactor userspace's emsr_fakewrite()
The old fakewrite would attempt to do a readmsr, which will fail.
However, we only need to do a readmsr if we read before writing.  Most
uses of this will do a write first.

Note that rdmsr and wrmsr will fail from userspace.  The MSR emulation
code is mostly just an unused copy of the kernel's, but it's useful to
prototype changes in userspace without requiring a kernel reboot.  i.e.
this is for debugging.

Signed-off-by: Barret Rhoden <>
Latest commit 9a1c439 Aug 22, 2019
Type Name Latest commit message Commit time
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Documentation iommu: add documentation Aug 19, 2019
kern vmm: x86: allow guests to poke MSR_IA32_PRED_CMD (XCC) Aug 22, 2019
scripts git: track the specific branch only Aug 19, 2019
tests ucbdma: userspace cbdma test Aug 19, 2019
tools bb: do not clobber the bash symlink Jul 11, 2019
.clang-format Treat tabs as having eight spaces instead of four Mar 24, 2019
.git-blame-ignore-revs Set up git blame to ignore the "8-space-tab commits" Mar 27, 2019
.gitignore Remove 'fs' from the gitignore May 22, 2018
.travis.yml Add AKAROS_TOOLCHAINS (XCC) May 30, 2019 Cleanup May 30, 2019
Kconfig qio: remove CONFIG_BLOCK_EXTRAS Jun 5, 2019
LICENSE Clean up licensing Sep 8, 2015
LICENSE-gpl-2.0.txt Clean up licensing Sep 8, 2015
LICENSE-lgpl-2.1.txt Clean up licensing Sep 8, 2015
LICENSE-plan9 Rename LICENSE-PLAN9 -> LICENSE-plan9 Sep 8, 2015
Makefile Fix 8 space tab formatting for non-C files Mar 26, 2019
Makelocal.template Use make -jX by default Jan 10, 2017
arch Kernel configuration uses Kconfig Jun 3, 2013
config-default Run default init script at boot when using defconfig May 30, 2019
include Modified the build system to use Kconfig Jun 1, 2013

About Akaros

Akaros is an open source, GPL-licensed operating system for manycore architectures. Its goal is to provide better support for parallel and high-performance applications in the datacenter. Unlike traditional OSs, which limit access to certain resources (such as cores), Akaros provides native support for application-directed resource management and 100% isolation from other jobs running on the system.

Although not yet integrated as such, it is designed to operate as a low-level node OS with a higher-level Cluster OS, such as Mesos, governing how resources are shared amongst applications running on each node. Its system call API and "Many Core Process" abstraction better match the requirements of a Cluster OS, eliminating many of the obstacles faced by other systems when trying to isolate simultaneously running processes. Moreover, Akaros’s resource provisioning interfaces allow for node-local decisions to be made that enforce the resource allocations set up by a Cluster OS. This can be used to simplify global allocation decisions, reduce network communication, and ultimately promote more efficient sharing of resources. There is limited support for such functionality on existing operating systems.

Akaros is still very young, but preliminary results show that processes running on Akaros have an order of magnitude less noise than on Linux, as well as fewer periodic signals, resulting in better CPU isolation. Additionally, its non-traditional threading model has been shown to outperform the Linux NPTL across a number of representative application workloads. This includes a 3.4x faster thread context switch time, competitive performance for the NAS parallel benchmark suite, and a 6% increase in throughput over nginx for a simple thread-based webserver we wrote. We are actively working on expanding Akaros's capabilities even further.

Visit us at


Instructions on installation and getting started with Akaros can be found in


Our current documentation is very lacking, but it is slowly getting better over time. Most documentation is typically available in the Documentation/ directory. However, many of these documents are outdated, and some general cleanup is definitely in order.

Mailing Lists

Want to join the developers mailing list?

Send an email to

Or visit our google group and click "Join Group"

Want to report a bug?

Create a new issue here.

Want to chat on IRC?

brho hangs out (usually alone) in #akaros on The other devs may pop in every now and then.


Instructions on contributing can be found in Documentation/


The Akaros repository contains a mix of code from different projects across a few top-level directories. The kernel is in kern/, userspace libraries are in user/, and a variety of tools can be found in tools/, including the toolchain.

The Akaros kernel is licensed under the GNU General Public License, version 2. Our kernel is made up of code from a number of other systems. Anything written for the Akaros kernel is licensed "GPLv2 or later". However, other code, such as from Linux and Plan 9, are licensed GPLv2, without the "or later" clause. There is also code from BSD, Xen, JOS, and Plan 9 derivatives. As a whole, the kernel is licensed GPLv2.

Note that the Plan 9 code that is a part of Akaros is also licensed under the Lucent Public License. The University of California, Berkeley, has been authorised by Alcatel-Lucent to release all Plan 9 software previously governed by the Lucent Public License, Version 1.02 under the GNU General Public License, Version 2. Akaros derives its Plan 9 code from this UCB release. For more information, see LICENSE-plan9 or here.

Our user code is likewise from a mix of sources. All code written for Akaros, such as user/parlib/, is licensed under the GNU LGPLv2.1, or later. Plan 9 libraries, including user/iplib and user/ndblib are licensed under the LGPLv2.1, but without the "or later". See each library for details.

Likewise, tools/ is a collection of various code. All of our contributions to existing code bases, such as GCC, glibc, and busybox, are licensed under their respective projects' licenses.

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