7 ms·

Your understanding is, I'm sorry if this comes across as hostile, absolute nonsense. You should actually consult the literature instead of reading Linus Torvald

Your understanding is, I'm sorry if this comes across as hostile, absolute nonsense. You should actually consult the literature instead of reading Linus Torvalds rants. Back in 1990, the Amoeba system revealed 2x improvement in throughput and 5x improvement in latency for its RPC over the SunRPC of the time. [1] Relative measurements for the V-System and Sprite were similar. QNX, a microkernel-based system with high commercial success and a long history (used by over 40 automotive manufacturers) has highly fast IPC by integrating message passing with the CPU scheduler. After years of research, Jochann Liedtke introduced L4 in 1996 [2] using only seven generalized calls with a 20x improvement in speed over prior art such as Mach. Mach, by the way, is the glaring exception to microkernel performance because of complicated message packing and port rights checking. Yet the Hurd developers are doing well in optimizing it, and to this day Mach is used to malign microkernels by people with no background on the subject. OKL4, in turn, has shipped in ~1.5 billion devices by 2012, powering the baseband processor behind nearly every mobile phone. [3] MINIX 3 further only shows a ~5-10% performance drop relative to monolithic Unixes, this for 2006. [4] They never learn. [1] http://www.scs.stanford.edu/nyu/03sp/sched/amoeba.pdf http://www.scs.stanford.edu/nyu/03sp/sched/amoeba.pdf [2] https://homes.cs.washington.edu/~bershad/590s/papers/towards-ukernels.pdf https://homes.cs.washington.edu/~bershad/590s/papers/towards... [3] http://www.creativemac.com/article/OK-Labs-Software-Surpasses-Milestone-of-15-Billion-Mobile-Device-Shipments--1842548 http://www.creativemac.com/article/OK-Labs-Software-Surpasse... [4] http://www.minix3.org/doc/ACSAC-2006.pdf http://www.minix3.org/doc/ACSAC-2006.pdf

caycep 11y ago
as an aside, how is Mach doing these days? I suppose the most visible use is OS X and I assume Apple's engineers have evolved it greatly to keep up with the times compared with the earlier versions of OS X?
- vezzy-fnord 11y ago
  Apple's XNU is de facto monolithic in nature. It simply reuses OSF Mach primitives to build the BSD Unix layer next to it. Mach IPC is used primarily for service discovery these days, I think, what with launchd being responsible for being the bootstrap server, which maintains name-port bindings for Mach services to call into. This is a side effect of Mach port namespaces being internal to tasks, and hence not having an intrinsic arbiter. In contrast though, the Hurd decentralizes this activity by just assigning a bootstrap port for the client making the RPC call to rendezvous with the server or library in question. These days, OS X seldom uses Mach IPC directly, but rather via XPC. Mach had a surprising resurgence in interest over NextBSD implementing a ton of compatibility layers and mangling Apple sources in a weird, misguided attempt to make FreeBSD the new OS X. We'll see how it turns out.
  - to3m 11y ago
    By way of example, you can't create a Mach task that isn't a BSD process as well: https://github.com/opensource-apple/xnu/blob/10.10/osfmk/kern/task.c#L534 https://github.com/opensource-apple/xnu/blob/10.10/osfmk/ker...
kabdib 11y ago
The Apple Newton used a microkernel inspired by Mach, with a custom MMU that reduced the cost of context switching. It was . . . okay. The number of cycles it actually took to do a lightweight message pass was dismaying, though. The newt would have benefited from a less partitioned design for the underlying page and storage management. I used another microkernel OS on a set-top box. Now that was a misery, but one I attribute more to the uncaring attitude of the company that wrote the STB's firmware than any inherent problem with their OS (a decade later, critical and customer-affecting race conditions are still present in their code). To be honest, their OS didn't help. I don't think microkernels are bad. Making bad choices about performance that affect performance, battery life and other things that customers care about is bad, and you might have to break some abstractions in your microkernel to address those.
- AceJohnny2 11y ago
  > Now that was a misery, but one I attribute more to the uncaring attitude of the company that wrote the STB's firmware than any inherent problem with their OS (a decade later, critical and customer-affecting race conditions are still present in their code). To be honest, their OS didn't help. Hmmm STMicro-based? :)
  - kabdib 11y ago
    68K, actually, and MIPS. Different platforms, same damned OS bugs. Let's hear it for portability :-)
simula67 11y ago
Didn't the Microsoft NT project start off as a micro kernel and then changed course to a hybrid model ? https://en.wikipedia.org/wiki/Hybrid_kernel https://en.wikipedia.org/wiki/Hybrid_kernel
- lobster_johnson 11y ago
  NT was never a microkernel. It has an intenral microkernel-like design, though; it's divided into cleanly separated modules, and modules may only communicate using a special IPC mechanism. But like OS X, the classic pieces (file systems, graphics, device drivers) run in kernel mode. Originally, graphics ran in user mode, but Windows 2000 moved it back into kernel mode for performance reasons. Vista got a new device driver model and a new graphics driver model (WDDM), which has a way for graphics to run partly in user mode. Vista and later also support user-mode device drivers.
  - orionblastar 11y ago
    Windows NT 3.1 was based on Microsoft OS/2 NT 3.0, it was originally Microsoft's version of OS/2 with the Windows 3>X GUI added to it instead of IBM's Presentation Manager. The NT Kernel and OS was designed to run DOS, POSIX, OS/2 1.X CLI apps (But not GUI) and 16 bit Windows and 32 bit Windows apps. Later on OS/2 and POSIX support got dropped. Microsoft OS/2 NT 3.0 was a rewrite of OS/2 for 32 bit systems, before that OS/2 was on 16 bit systems with 1.X and IBM and Microsoft fought over 2.0 standards, and Microsoft stopped support for OS/2 and focused on Windows instead. Then renamed their OS/2 to NT for New Technologies. The Interesting thing about Windows NT was that Microsoft had plans to port it to different processors and eventually dropped those plans and stuck with X86 processors instead. https://en.wikipedia.org/wiki/Windows_NT https://en.wikipedia.org/wiki/Windows_NT It was designed as a modified microkernel.
    - rodgerd 11y ago
      > The Interesting thing about Windows NT was that Microsoft had plans to port it to different processors The didn't plan it, they did it. I was looking after Windows NT on Alpha processors at one job. I never personally saw the NT on PowerPC or MIPS, though they did exist.

caycep 11y ago

as an aside, how is Mach doing these days? I suppose the most visible use is OS X and I assume Apple's engineers have evolved it greatly to keep up with the times compared with the earlier versions of OS X?

vezzy-fnord 11y ago
Apple's XNU is de facto monolithic in nature. It simply reuses OSF Mach primitives to build the BSD Unix layer next to it. Mach IPC is used primarily for service discovery these days, I think, what with launchd being responsible for being the bootstrap server, which maintains name-port bindings for Mach services to call into. This is a side effect of Mach port namespaces being internal to tasks, and hence not having an intrinsic arbiter. In contrast though, the Hurd decentralizes this activity by just assigning a bootstrap port for the client making the RPC call to rendezvous with the server or library in question. These days, OS X seldom uses Mach IPC directly, but rather via XPC. Mach had a surprising resurgence in interest over NextBSD implementing a ton of compatibility layers and mangling Apple sources in a weird, misguided attempt to make FreeBSD the new OS X. We'll see how it turns out.
- to3m 11y ago
  By way of example, you can't create a Mach task that isn't a BSD process as well: https://github.com/opensource-apple/xnu/blob/10.10/osfmk/kern/task.c#L534 https://github.com/opensource-apple/xnu/blob/10.10/osfmk/ker...

kabdib 11y ago

The Apple Newton used a microkernel inspired by Mach, with a custom MMU that reduced the cost of context switching. It was . . . okay. The number of cycles it actually took to do a lightweight message pass was dismaying, though. The newt would have benefited from a less partitioned design for the underlying page and storage management. I used another microkernel OS on a set-top box. Now that was a misery, but one I attribute more to the uncaring attitude of the company that wrote the STB's firmware than any inherent problem with their OS (a decade later, critical and customer-affecting race conditions are still present in their code). To be honest, their OS didn't help. I don't think microkernels are bad. Making bad choices about performance that affect performance, battery life and other things that customers care about is bad, and you might have to break some abstractions in your microkernel to address those.

AceJohnny2 11y ago
> Now that was a misery, but one I attribute more to the uncaring attitude of the company that wrote the STB's firmware than any inherent problem with their OS (a decade later, critical and customer-affecting race conditions are still present in their code). To be honest, their OS didn't help. Hmmm STMicro-based? :)
- kabdib 11y ago
  68K, actually, and MIPS. Different platforms, same damned OS bugs. Let's hear it for portability :-)

simula67 11y ago

Didn't the Microsoft NT project start off as a micro kernel and then changed course to a hybrid model ? https://en.wikipedia.org/wiki/Hybrid_kernel https://en.wikipedia.org/wiki/Hybrid_kernel

lobster_johnson 11y ago
NT was never a microkernel. It has an intenral microkernel-like design, though; it's divided into cleanly separated modules, and modules may only communicate using a special IPC mechanism. But like OS X, the classic pieces (file systems, graphics, device drivers) run in kernel mode. Originally, graphics ran in user mode, but Windows 2000 moved it back into kernel mode for performance reasons. Vista got a new device driver model and a new graphics driver model (WDDM), which has a way for graphics to run partly in user mode. Vista and later also support user-mode device drivers.
- orionblastar 11y ago
  Windows NT 3.1 was based on Microsoft OS/2 NT 3.0, it was originally Microsoft's version of OS/2 with the Windows 3>X GUI added to it instead of IBM's Presentation Manager. The NT Kernel and OS was designed to run DOS, POSIX, OS/2 1.X CLI apps (But not GUI) and 16 bit Windows and 32 bit Windows apps. Later on OS/2 and POSIX support got dropped. Microsoft OS/2 NT 3.0 was a rewrite of OS/2 for 32 bit systems, before that OS/2 was on 16 bit systems with 1.X and IBM and Microsoft fought over 2.0 standards, and Microsoft stopped support for OS/2 and focused on Windows instead. Then renamed their OS/2 to NT for New Technologies. The Interesting thing about Windows NT was that Microsoft had plans to port it to different processors and eventually dropped those plans and stuck with X86 processors instead. https://en.wikipedia.org/wiki/Windows_NT https://en.wikipedia.org/wiki/Windows_NT It was designed as a modified microkernel.
  - rodgerd 11y ago
    > The Interesting thing about Windows NT was that Microsoft had plans to port it to different processors The didn't plan it, they did it. I was looking after Windows NT on Alpha processors at one job. I never personally saw the NT on PowerPC or MIPS, though they did exist.