ron@gatech.UUCP (06/05/84)
.....How do they implement COMMON in f77? Does anyone know of a way to share a data segment between several processes running concurrently on a vax 780 so that data written to the data segment by one is visible to the others? Is there a loader option which permits shared write segments? Please respond by mail. I have done this under VMS and its possible if not straightforward. I have heard that unix doesn't have a good way but it seems that there should be something I can do. thanks. ron@gatech -- Ron Hutchins
gwyn@brl-vgr.UUCP (06/08/84)
The facility you are requesting is called "shared memory". It is available on UNIX System V, but not on 4.?BSD.
karl@cygnet.UUCP (Karl Danz) (06/08/84)
[] We needed shared memory support in 4.2 and after some investigation realized that Berkeley had started to implement it. (Check out "man page" for mmap system call in the System Manual.) We put in mods to support shared memory using some of the "ifdef'd out" code in the 4.2 distribution as a starting point. Our needs were small enough (less than 100K) that we simply set up a fixed buffer in kernel storage to which we point the page table entries of processes requesting use of the shared memory... crude, but it works for us. If anyone is interested, I can send our mods. Karl Danz Cygnet Systems
tjt@kobold.UUCP (06/08/84)
Support for shared memory segments is in System V, but not System III.
--
Tom Teixeira, Massachusetts Computer Corporation. Westford MA
...!{ihnp4,harpo,decvax}!masscomp!tjt (617) 692-6200 x275fair@dual.UUCP (Erik E. Fair) (06/12/84)
Karl's mods to 4.2BSD sound EXACTLY like what System V shared memory IS.
Erik E. Fair ucbvax!fair fair@ucb-arpa.ARPA
dual!fair@Berkeley.ARPA
{ihnp4,ucbvax,cbosgd,decwrl,amd70,fortune,zehntel}!dual!fair
Dual Systems Corporation, Berkeley, California