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7.4 Process Buffers vs. System Buffers

When a message is sent for which a receive has not yet been issued, the message goes into a system buffer if its length is 100 bytes or less. It is then referred to as a pending message. The message will be received only after a receive has been issued for it. If a receive had already been issued, then the message bypasses the system buffer and goes directly to the buffer of the receiving process. The cprobe() and iprobe() calls determine whether there is a message pending for a process. If the length of the message is more than 100 bytes, then it will remain in the sender's buffer and not go into a system buffer.