strace without arguments writes all STREAMS event trace messages from all drivers and modules to its standard output. These messages are obtained from the STREAMS log driver (see log(7D)). If arguments are provided, they must be in triplets of the form mid, sid, level, where mid is a STREAMS module ID number, sid is a sub-ID number, and level is a tracing priority level. Each triplet indicates that tracing messages are to be received from the given module/driver, sub-ID (usually indicating minor device), and priority level
equal to, or less than the given level. The token all may be used for any member to indicate no restriction for that attribute.
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There is no restriction to the number of strace processes opening the STREAMS log driver at a time.
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The log-driver records the list of the triplets specified in the command invocation, and compares each potential trace message against this list to decide if it should be formatted
and sent up to the strace process. Hence, long lists of triplets will have a greater impact on overall STREAMS performance. Running strace will have the most impact
on the timing of the modules and drivers generating the trace messages that are sent to the strace process. If trace messages are generated faster than the strace
process can handle them, some of the messages will be lost. This last case can be determined by examining the sequence numbers on the trace messages output.