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>On current hardware, RPC is expensive no matter how you optimize You mean IPC? While hardware support could make it faster, it is already plenty fast. The w

by copergi 12y ago

>On current hardware, RPC is expensive no matter how you optimize You mean IPC? While hardware support could make it faster, it is already plenty fast. The whole "L4 only introduces 3% overhead" thing is pretty old news at this point. >I have played a lot with L4 Then you should know that the performance myths that come from mach's slowness are not accurate. >Any user or application can't replace a privileged system server Multi-user systems are a vanishingly small minority at this point. I don't think "you need to be in control of your computer" is a huge show stopper.

Rusky 12y ago
I mean RPC, because that is the common use case of IPC between applications and servers in microkernel systems. It is more expensive than shared library calls or system calls no matter how much you optimize it on current architectures. I'm also well aware of L4's performance vs Mach, but like I said: "instead of the lingering 'eh, it's a little slower but we can ignore that,' exokernels provide much better opportunities for optimization and tend to be much faster" than monolithic or microkernel designs. For example, MIT's Cheetah HTTP static file server (comparable to squid, at the time named Harvest) achieved a 4x performance improvement just by moving to an exokernel and an 8x performance improvement by implementing some of the optimizations I've described in previous comments. This depends on the ability to bypass the privileged servers a microkernel typically uses. Microkernels are nice for security, for a few percent overhead, and that's good, but that's about all they do, so they're not seen as worthwhile for many uses. Exokernels can provide the same level of security while also providing far greater flexibility and performance. This essentially provides, with a performance gain, what current data centers use virtualization for, which is another few-percent-slowdown.
- copergi 12y ago
  I can't tell if that is the most subtle trolling I've seen since the 90s, or if you are seriously saying "yes I know I was lying, but I am still lying so it is cool".

by copergi 12y ago

Rusky 12y ago

I mean RPC, because that is the common use case of IPC between applications and servers in microkernel systems. It is more expensive than shared library calls or system calls no matter how much you optimize it on current architectures. I'm also well aware of L4's performance vs Mach, but like I said: "instead of the lingering 'eh, it's a little slower but we can ignore that,' exokernels provide much better opportunities for optimization and tend to be much faster" than monolithic or microkernel designs. For example, MIT's Cheetah HTTP static file server (comparable to squid, at the time named Harvest) achieved a 4x performance improvement just by moving to an exokernel and an 8x performance improvement by implementing some of the optimizations I've described in previous comments. This depends on the ability to bypass the privileged servers a microkernel typically uses. Microkernels are nice for security, for a few percent overhead, and that's good, but that's about all they do, so they're not seen as worthwhile for many uses. Exokernels can provide the same level of security while also providing far greater flexibility and performance. This essentially provides, with a performance gain, what current data centers use virtualization for, which is another few-percent-slowdown.

copergi 12y ago
I can't tell if that is the most subtle trolling I've seen since the 90s, or if you are seriously saying "yes I know I was lying, but I am still lying so it is cool".