Ben Coman wrote:
(whoops forgot to cross-post)
Eliot Miranda wrote:
Hi Ben,
On Dec 19, 2014, at 8:08 PM, Ben Coman <btc@openInWorld.com> wrote:
Just some thoughts that arose as I skipped along the web...
With the idea of using Pharo in the cloud, I was thinking of how PharoNOS[1] is basing off top of the Linux kernel, but the examples indicate its operating in User Mode. So I was wondering about performance being greater[2] if the CogVM ran in Kernel Mode. However maybe this could get tangled in the GPL license of the kernel.
Now I believe FreeBSD/NetBSD license is compatible with COG's MIT license, so that seems a better option for eliminating layers of the operating system. They both[3][4] have pre-built Amazon Machine Images to run on EC2, as well as instructions[5] to build your own AMI. So potentially we could build an AMI with the CogVM linked to the FreeBSDKernel operating in Kernel Mode, with no User Mode. The lack of direct access to memory from the Image, and probably single application focus should be sufficient security to forgo User Mode, and run faster.
But we could go a step further. Runing in the cloud relies heavily on virtualisation, and for performance[6], most likely on the OS's paravirtualisation interface - to Xen for example. So from Cog, why not interface direct to the Xen FrontEndDriver[7] and eliminate the DomU operating system all together. What I understand from [6] is that Xen's paravirtualisation hooks makes it much easier to boot, than booting on the bare metal of a fully-virtualised system. So the former seems more achievable than the latter (which was the only option in years past), and also be more portable as technology evolves, to any platform Xen runs on.
Squeak/Pharo on Cog-Xen could be a good choice for a Cloud Operating System[8]. Maybe a good student research project?
This sounds really cool, but could you analyse a bit further?
- what key economic and managerial benefits accrue from this configuration?
I'll put some more thought into this, but just off the top of my head (so it turned out more technical than economic/managerial):
* Eliminates performance overhead of system call context switching. Although this is replaced by hypercalls, it removes one layer on hypervisor systems, which plausibly is going to be EVERYTHING in the future.
* Eliminate performance overhead of OS networking stack http://roscidus.com/blog/blog/2014/08/15/optimising-the-unikernel/
* Data from virtual devices is event driven.
* More easily portable to different ARM platforms. Xen will present a common interface to hide platform idiosyncrasies. --> More widespread embedded use Cog. http://www.slideshare.net/xen_com_mgr/free-rtos-xensummit
* Run databases in their own domain.
* Isolate plugin memory space. Rather than linking plugins into Cog, potentially threatening its stability, run them in a separate domain and use high-speed inter-domain shared memory. http://www.cs.ucsb.edu/~nanli/projects/cs270.pdf
* Have a cloud community of thousands** of Images running each in their own domain, communicating with high-speed inter-domain shared memory. ** presumptive figure - would need to check scaling ability
* Data sharing on high density hosting providers. Not sure if its there yet, but may get Copy-On-Write http://www-archive.xenproject.org/files/xensummit_fall07/18_GregorMilos.pdf
* In very large Images, which Spur will allow, perhaps a better way to snapshot an Image is via virtual machine snapshotting using Copy-On. http://www.cercs.gatech.edu/tech-reports/tr2010/git-cercs-10-05.pdf
* Rather than convert the Cog/Image to be multi-threaded, could have many grid nodes running their own domain, communicating with high speed shared memory. http://www.cs.ucsb.edu/~nanli/projects/cs270.pdf http://osnet.cs.binghamton.edu/publications/hines07memx.pdf
* AMD's hardware virtualisation eliminated a Ring and also segmented memory protection used by virtualisation to separate address spaces, so 64-bit AMD can be slower. Eliminating the OS kernel layer probably bypasses this limitation since there would be only two levels - Hypervisor & Cog. https://lse.epita.fr/data/2011-lse-summer-week/xen.pdf
* Its where all the cool kids hang out --> marketing opportunity
* Security versus lines of code... Linux = 15.9 million (3.6 Kernel) OSX = 86 million FreeBSD = 6.25 million OpenSolaris = 10 million Windows = 64 million Xen-ARM = 90,000 Xen-x86 = 140,000 https://www.google.com/fusiontables/DataSource?docid=12Eg7Ru1CH5MIjomcfjaGKe... http://wiki.xen.org/wiki/Xen_ARM_with_Virtualization_Extensions_whitepaper
- what infrastructure is missing? (e.g. what key drivers need implementing?)
I'll need to understand Cog more. As a start, here are some porting and API docs...
http://events.linuxfoundation.org/sites/events/files/slides/Porting%20FreeBS...
http://oss.org.cn/ossdocs/server_storage/xen/interface/interface.html
http://www.informit.com/articles/article.aspx?p=1160234&seqNum=4
https://lse.epita.fr/data/2011-lse-summer-week/xen.pdf
https://github.com/cloudius-systems/osv/blob/master/drivers/xenfront-xenbus....
cheers -ben
[1] http://pillarhub.pharocloud.com/hub/mikefilonov/pharonos [2] http://blog.codinghorror.com/understanding-user-and-kernel-mode/ [3] http://www.daemonology.net/freebsd-on-ec2/ [4] http://wiki.netbsd.org/amazon_ec2/amis/ [5] http://wiki.netbsd.org/amazon_ec2/build_your_own_ami/ [6] http://wiki.xen.org/wiki/Virtualization_Spectrum [7] http://wiki.xen.org/wiki/FrontendDriver [8] http://wiki.xen.org/wiki/Cloud_Operating_Systems
Eliot (phone)