5 ms·

Been done before (some would say to death), and the reason we have memory protection between applications is forgotten because people don't realize how nice it

Been done before (some would say to death), and the reason we have memory protection between applications is forgotten because people don't realize how nice it is. Sure, sure, your big "well engineered" web browser needs direct access to the hardware for speed, but painful experience has taught us that giving apps programmers direct access to hardware is a recipe for failure. Besides, there are already plenty of workarounds to get faster (eg, mmap) or even direct access to hardware from userland, not to mention the myriad of virtualization and protection schemes and levels in userland (eg, SELinux). This seems like a solution in search of already solved problems. Although as a research project, it does seem interesting . . .

rbanffy 12y ago
> Been done before (some would say to death) How is that George Santayana thing? "Those who cannot remember the past are condemned to repeat it"? I like seeing new ideas being tested in the OS arena. It's a real shame the two dominant OSs these days are Unix and VMS. I refuse to believe these two are the best humans can come up with.
- mikeash 12y ago
  From "The Rise of 'Worse is Better'", written in 1989: "The good news is that in 1995 we will have a good operating system and programming language; the bad news is that they will be Unix and C++." The predicted date was a little early, but otherwise he pretty much got it right. I think that, from a late 80s Lisp perspective, modern Windows fits into the "UNIX" category, and Java/C#/ObjC/whatever are close enough to C++ to count.
  - trhway 12y ago
    >The predicted date was a little early wouldn't say so - my first Linux machine (slackware, shoebox of diskettes :) i installed exactly in the 95 :) >from a late 80s Lisp perspective, modern Windows fits into the "UNIX" category while psychotropic mind-altering effects of Lisp are well known, i'd doubt that it can produce such perception changes or even in such a direction.
    - mikeash 12y ago
      Windows and UNIX are not so different. Monolithic kernels written in C or C++, permissions largely done with user granularity, byte-addressed memory, virtual memory with per-process address spaces, no hardware support for tagged pointers or garbage collection.... Compared to the variety that's gone before, they look nearly identical in their fundamentals.
- Executor 12y ago
  Thucydides?
chadgeidel 12y ago
I would go even further and say that apps developers don't want to write a networking stack, display driver, roll their own sound implementation, etc. It sounds like the "bad old days" of DOS where games had to have their own implementation of these things.
- wmf 12y ago
  That's why Arrakis provides that functionality through a library.
sounds 12y ago
Good points. Indulge me for a minute while I try to formulate what they might say in response: most of the complexity of an OS is device drivers. You're right, the basics of process isolation, scheduling, and resource allocation are pretty dull. Maybe the UW project makes the move to userspace official? At 1,000,000 packets per second it is more efficient to put the whole network stack in userspace. Assume similar gains can be had for all types of hardware, and shared libraries eliminate the overhead of loading the whole network stack every time you run 'ping'. That's just a 30-second pitch for the idea. Userspace is not new (see: Mach). I think what is changing is the average lifetime of each process. Both desktops and servers are beginning to become a commodity to the point where the old reasons for not using a microkernel are starting to become irrelevant: e.g. message passing cost isn't as much of a problem if the file server runs 'smbd' 99% of the time and that is the only really performance-sensitive application. Likewise for a desktop, except the running process is 'Chrome', or for a tablet running 'dalvikvm'. Really it's a move away from code complexity that wasn't possible before but is becoming possible.
- npsimons 12y ago
  So are we talking Microkernel here or something else? Sorry to constrain by categorizing, but it's what I do sometimes :) and I am thinking of some OSes (mostly research/academic) that went this way (of no layers between userland and the hardware) that weren't Microkernels, but I can't remember any names right now. I have to admit, part of what keeps my interest in this is that I used to dabble in OSes and I haven't gotten to for quite some time :( EDIT: Exokernel was what I was remembering (I think; https://en.wikipedia.org/wiki/Exokernel https://en.wikipedia.org/wiki/Exokernel). I can see some of the advantages, but as a current maintenance programmer and previous RTLinux hacker, I have to say I have my doubts about giving most programmers direct access to hardware :) That being said, giving programmers (and admins!) easier access to containerization, virtualization, or just intra-process protection in general would be a good idea. As I've said, there are plenty of options right now, but none seem to be well documented or advertised. There was a CACM article a while back that predicted a future in which you had one smartphone, but it had split domains for work and personal apps and data. Interesting stuff, and as you say, finally becoming possible.
bri3d 12y ago
Arrakis doesn't eliminate memory protection or process isolation, nor does it give applications direct hardware access. It takes advantage of modern hardware virtualization capabilities to present certain virtual devices to the guest applications, eliminating the kernel from the I/O path for critical operations like receiving a packet. Read this paper: http://arrakis.cs.washington.edu/wp-content/uploads/2013/04/arrakis-tr-ver2.pdf http://arrakis.cs.washington.edu/wp-content/uploads/2013/04/...

rbanffy 12y ago

> Been done before (some would say to death) How is that George Santayana thing? "Those who cannot remember the past are condemned to repeat it"? I like seeing new ideas being tested in the OS arena. It's a real shame the two dominant OSs these days are Unix and VMS. I refuse to believe these two are the best humans can come up with.

mikeash 12y ago
From "The Rise of 'Worse is Better'", written in 1989: "The good news is that in 1995 we will have a good operating system and programming language; the bad news is that they will be Unix and C++." The predicted date was a little early, but otherwise he pretty much got it right. I think that, from a late 80s Lisp perspective, modern Windows fits into the "UNIX" category, and Java/C#/ObjC/whatever are close enough to C++ to count.
- trhway 12y ago
  >The predicted date was a little early wouldn't say so - my first Linux machine (slackware, shoebox of diskettes :) i installed exactly in the 95 :) >from a late 80s Lisp perspective, modern Windows fits into the "UNIX" category while psychotropic mind-altering effects of Lisp are well known, i'd doubt that it can produce such perception changes or even in such a direction.
  - mikeash 12y ago
    Windows and UNIX are not so different. Monolithic kernels written in C or C++, permissions largely done with user granularity, byte-addressed memory, virtual memory with per-process address spaces, no hardware support for tagged pointers or garbage collection.... Compared to the variety that's gone before, they look nearly identical in their fundamentals.
Executor 12y ago
Thucydides?

chadgeidel 12y ago

I would go even further and say that apps developers don't want to write a networking stack, display driver, roll their own sound implementation, etc. It sounds like the "bad old days" of DOS where games had to have their own implementation of these things.

wmf 12y ago
That's why Arrakis provides that functionality through a library.

sounds 12y ago

Good points. Indulge me for a minute while I try to formulate what they might say in response: most of the complexity of an OS is device drivers. You're right, the basics of process isolation, scheduling, and resource allocation are pretty dull. Maybe the UW project makes the move to userspace official? At 1,000,000 packets per second it is more efficient to put the whole network stack in userspace. Assume similar gains can be had for all types of hardware, and shared libraries eliminate the overhead of loading the whole network stack every time you run 'ping'. That's just a 30-second pitch for the idea. Userspace is not new (see: Mach). I think what is changing is the average lifetime of each process. Both desktops and servers are beginning to become a commodity to the point where the old reasons for not using a microkernel are starting to become irrelevant: e.g. message passing cost isn't as much of a problem if the file server runs 'smbd' 99% of the time and that is the only really performance-sensitive application. Likewise for a desktop, except the running process is 'Chrome', or for a tablet running 'dalvikvm'. Really it's a move away from code complexity that wasn't possible before but is becoming possible.

npsimons 12y ago
So are we talking Microkernel here or something else? Sorry to constrain by categorizing, but it's what I do sometimes :) and I am thinking of some OSes (mostly research/academic) that went this way (of no layers between userland and the hardware) that weren't Microkernels, but I can't remember any names right now. I have to admit, part of what keeps my interest in this is that I used to dabble in OSes and I haven't gotten to for quite some time :( EDIT: Exokernel was what I was remembering (I think; https://en.wikipedia.org/wiki/Exokernel https://en.wikipedia.org/wiki/Exokernel). I can see some of the advantages, but as a current maintenance programmer and previous RTLinux hacker, I have to say I have my doubts about giving most programmers direct access to hardware :) That being said, giving programmers (and admins!) easier access to containerization, virtualization, or just intra-process protection in general would be a good idea. As I've said, there are plenty of options right now, but none seem to be well documented or advertised. There was a CACM article a while back that predicted a future in which you had one smartphone, but it had split domains for work and personal apps and data. Interesting stuff, and as you say, finally becoming possible.

bri3d 12y ago

Arrakis doesn't eliminate memory protection or process isolation, nor does it give applications direct hardware access. It takes advantage of modern hardware virtualization capabilities to present certain virtual devices to the guest applications, eliminating the kernel from the I/O path for critical operations like receiving a packet. Read this paper: http://arrakis.cs.washington.edu/wp-content/uploads/2013/04/arrakis-tr-ver2.pdf http://arrakis.cs.washington.edu/wp-content/uploads/2013/04/...