[TUHS] Re: Clever code (was Re: Re: Stdin Redirect in Cu History/Alternatives?

Don't see how unless they put multiple related services in the same address space, which reduces context switching but tends toward a monokernel (& increased coupling). Unless I am misunderstanding you. > On Dec 14, 2022, at 6:54 PM, Larry McVoy <lm(a)mcvoy.com> wrote: > > Wasn't there some statement that QNX dropped some of these? Copy plus > context switch? > > On Wed, Dec 14, 2022 at 04:29:45PM -0800, Bakul Shah wrote: >> On Dec 11, 2022, at 7:09 PM, Andrew Warkentin <andreww591(a)gmail.com> wrote: >>> >>> It's not necessarily true that microkernels are significantly slower. >> >> uKernels are usually quite fast as they do so little. What can be slow >> is emulating a Unix like OS on top due to context switches. For instance, >> a user process doing read() will have the following context switches: >> >> userProc->uK->FileSystem->uK->diskDriver->uk->FileSysem->uK->userProc >> >> or worse (I didn't account for a few things). Because of this even some >> uKernels run a few critical services + drivers in the supervisor mode. >> But overall slowdown of such a unix emulation will very much depend on the >> workload and also what kind of performance improvements you are willing to >> try in a complex kernel vs same services running in user mode. >> >> At present the linux kernel has about 31+ Million lines (accounting for >> all architectures, filesystems, device drivers etc.). The FreeBSD 13.x >> kernel is about 8.7M LoC (of which 44-45% are in device drivers). I only >> counted .c and .h files. In contract FreeBSD 2.2.2 kernel has ~554K LoC. >> This LoC growth is entirely understandable but I wonder how things may >> have turned out in an alternate universe of uKernel based designs.... > > -- > --- > Larry McVoy Retired to fishing http://www.mcvoy.com/lm/boat