| commit | 56fbd8e93bd3438b186cc144a5e529018109f6e1 | [log] [tgz] |
|---|---|---|
| author | Barret Rhoden <brho@cs.berkeley.edu> | Fri Jan 13 17:19:13 2017 -0500 |
| committer | Barret Rhoden <brho@cs.berkeley.edu> | Wed Jan 18 10:00:03 2017 -0500 |
| tree | a830df0c0b8195e9d26cb386e71d372984962f6f | |
| parent | e88301d338aaeb6814653a9a9c57e8bb5ee2d49b [diff] |
x86: vmm: Finalize to owning_proc, not cur_proc. Similar to a previous bug, x86_finalize_vmtf() assumed the TF belonged to cur_proc, but it actually belongs to owning_proc. If we finalize a TF on a core that runs proc's/kthreads concurrently, then we could have a situation where cur_proc != owning_proc. Then we'd try finding a GPC for the other process, instead of the VMM. Yikes! This was relatively easy to make happen regularly: run vmrunkernel as an SCP under strace from ssh. I think I triggered it with perf at some point too. Here's the main debugging info that pointed me the right way: couldn't find a gpc, p 284, guest_pcoreid 0 kernel panic at kern/arch/x86/vmm/vmm.c:206, from core 0: assertion failed: gpc Entering Nanwan's Dungeon on Core 0 (Ints off): Type 'help' for a list of commands. ROS(Core 0)> ps PID Name State Parent ------------------------------------------------- 15 /bin/cs WAITING 0 12 /bin/ipconfig WAITING 0 1 bash WAITING 0 269 /bin/dropbear WAITING 0 284 strace RUNNABLE_S 275 274 /bin/dropbear WAITING 269 270 /bin/bash WAITING 1 285 vmrunkernel RUNNING_S 284 275 -sh WAITING 274 ROS(Core 0)> bt Stack Backtrace on Core 0: #01 [<0xffffffffc201ed74>] in mon_backtrace #02 [<0xffffffffc201fd77>] in monitor #03 [<0xffffffffc200ca1a>] in _panic #04 [<0xffffffffc2134e9c>] in unload_guest_pcore #05 [<0xffffffffc21320d8>] in arch_finalize_ctx #06 [<0xffffffffc205d1bb>] in copy_current_ctx_to #07 [<0xffffffffc204d70c>] in __notify #08 [<0xffffffffc205d71f>] in process_routine_kmsg #09 [<0xffffffffc2051665>] in proc_restartcore Note that the lookup was using PID 284 (strace), but the VM was 285. Signed-off-by: Barret Rhoden <brho@cs.berkeley.edu>
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 akaros.org
Instructions on installation and getting started with Akaros can be found in GETTING_STARTED.md
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.
Send an email to akaros+subscribe@googlegroups.com.
Or visit our google group and click “Join Group”
Create a new issue here.
brho hangs out (usually alone) in #akaros on irc.freenode.net. The other devs may pop in every now and then.
Instructions on contributing can be found in Documentation/Contributing.md.
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.