Shared Memory on SCO Xenix

[Kean Johnston]

Please could someone clarify a point for me relating to shared memory under
SCO Xenix, specifically Xenix/386 release 2.3.2 or 2.3.3.
In his excelent book "Advanced Unix Programming" by Marc J. Rochkind,
in the chapter on IPC's and shared memory he states that under Xenix, after
having mapped a segment as shared, you have to unmap it before you can
issue any system calls. This means that you have to keep on mapping and
unmapping the shared data segment each time you need to make a system call.
Is this still true of Xenix, or is the book just outdated. It WAS written
6 years ago after all.
Also, is there any MAJOR speed advantage of using shared memory over
semaphores? Anyone really pushed semaphores to the limit out there ?
Any help at will would be greatly appreciated.
Thanks in advance,


-- 
 Kean Johnston: kean at pscnet.UUCP    Bang: ..!ddsw1!olsa99!tabbs!pscnet!kean
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