[net.unix-wizards] Sys 5 Message Queue parameters

stevens@hsi.UUCP (Richard Stevens) (10/24/86)

I have a question concerning the parameters used for System 5
message queues.  After looking at the System 5.2 VAX release
and the same parameters in ULTRIX-32m V1.2 (param.h),
both have the following values:

        MSGMAX  8192    max message size in bytes
        MSGMNB 16384    max #bytes on any one queue
        MSGSSZ     8    message "segment" size - bytes ??
        MSGSEG  1024    number of message "segments"

From the code it appears that (8 * 1024) bytes are allocated for the
entire data area for all messages in the system.  That seems very
small, given that any single message can be that size, and given
that the maximum number of bytes on any queue is specified as being
twice that amount.  Am I missing something here ??

        Richard Stevens
        Health Systems International, New Haven, CT
           ihnp4 ! hsi ! stevens