Neal H Walfield wrote:
>> I was referring to the ipc, which takes place entirely in the kernel.
I do not believe the exokernel itself handles IPC. In fact, it is my
understanding that it essentially multiplexes the raw hardware. A set of
libraries, which are callable by user applications, implement the
traditional operating system services.
> > Consequently, for certain operations, say perhaps an
> > IPC send() or recv(), that a context switch would not be required.
> Why do you say that? If you have to change tasks, you will still need to
> trap to the kernel; the server and the client will (likely have different
> uids so cannot touch each other's page tables etc). Correct me if I am
You will never eliminate task switching in a multitasking system. I'm not
referring to the context switch that occurs when scheduling another task to
run. I'm suggesting that sending an IPC message, for instance, might be
accomplished by the libraries without having to trap to the kernel.
> I am throughly dissatisfied with Mach; it has many shortcomings that
> need to be addressed before it will ever be ready for end users. I
> believe that they will only be fixed by 64-bit hardware.
I believe this is true of GNU Mach. The Linux glue code is a giant bandaid.
There is no SMP support. No native PCI support. User space device drivers
have been disabled. Yada, yada, yada. However, in general, Mach has
already been used in commercial systems. NextStep was fairly successful as
a Unix desktop. Apple's OS/X and OSF/1 are also Mach-based. Rashid,
Barrera, and other CMU members of the Mach project, who were lured away to
Microsoft R & D, did many research projects with Mach. They ported Mach to
the Intel Paragon, supporting two thousand parallel processors and developed
an enhanced virtual memory subsystem (Odin) for accommodating such massively
That said, Mach is still aging and there may be a better long-term
> > End users, however, won't care about conceptual superiority -- they'll
> > for real world justification for choosing a particular platform.
> To quote Roland for a minute:
> We're way ahead of you here. The Hurd has always been on the cutting edge
> of not being good for anything.
What does this mean? We don't care? To quote Shakespeare: "Angels and
ministers of Christ defend us."
- RE: Samba
- From: OKUJI Yoshinori <email@example.com>