[rtl] virtual memory in RTL

[Alain Rollé]

Hi,

First of all : thanks for the replies to my questions concerning the rtl_sched module.

My next problem : I am comparing the design of RTLinux with the design of SOLARIS RT.
In the Solaris white papers, one can find the following :

In a virtual memory system, any memory reference can potentially cause a page fault. The time required to bring the referenced data into physical memory from disk can cause a real-time application to lose its determinism. The Solaris Operating Environment addresses this problem by allowing the locking of a process' pages into memory using mlock(3C) or mlockall(3C).

If I understand well, this problem does not occur in RTL because virtual memory is not a feature which  is supported by the Real Time kernel. This makes me wonder, however, how the RT kernel obtains memory for the real time tasks. Is it a fixed partition of memory that never gets swapped out ? How does it work ?

Next question :
To avoid jitter, the Solaris Operating Environment provides for early binding of dynamic libraries. By setting the LD_BIND_NOW environment variable to "1", libraries are bound at application startup time.

I presume the same technique is used in RTLinux ? If not, how is it done ?

To end with, one more question :
In the RTL manifesto is stated that :
"You can have deterministic worst case behaviour time on Solaris RT, but the worst case is really worse than you might be willing to tolerate"
Can anyone give me an indication of the worst case time between the moment a hardware interrupt is detected by the processor and the moment an interrupt handler starts to execute with Solaris RT. I can't seem to find these figures on the sun site.

Thanks a lot,

Alain.