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SubjectRe: a joint letter on low latency and Linux
On Sun, Jul 02, 2000 at 04:43:09PM -0400, Albert D. Cahalan wrote:
> Digital UNIX (now Tru64, was OSF/1) uses self-modifying code to
> create a generic kernel that can do, if I remember right:
>
> 1. plain
> 2. real-time
> 3. SMP
> 4. real-time SMP
> 5. lock debugging

I have a simple suggestion: When asserting that an OS has "real time"
capabilities, include either the adjective "hard" and supply a time
worst case interrupt latency on a representative hardware platform or
include "soft" and supply a characterization of "typical" interrupt
latencies and worst case number of violations.

> on a real i386 without being slow on a 486. Modules could work for
> SMP, huge memory, and normal kernels. Exact process accounting could
> be part of every kernel, but NOPed out at runtime if not enabled.
> Perhaps even RT-Linux could use this ability.

Nops cost too but RTLinux V3 in the x86 does do some on-line code
patching for Linux so that we can keep the Linux mods simple and
pay a time cost only when we move into RT mode.




--
---------------------------------------------------------
Victor Yodaiken
FSMLabs: www.fsmlabs.com www.rtlinux.com
FSMLabs is a servicemark and a service of
VJY Associates L.L.C, New Mexico.


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