void tracemem(address, size_t nbytes)
void tracemem(address, size_t nbytes, size_t dbytes)

The tracemem action takes a D expression as its first argument, address, and a constant as its second argument, nbytes. The tracemem action copies the memory from the address specified by address into the directed buffer for the length specified by nbytes. If only two arguments are provided, dtrace dumps the entire contents of the buffer.

In the second format, the tracemem action takes an additional, third argument, dbytes, which is a D expression that is computed dynamically. The result is used to limit the number of bytes that are displayed. If the result is less than zero or greater than nbytes, the result is ignored and tracemem behaves as though it is called by using the two-argument form. Otherwise, dtrace dumps only the dbytes bytes of the directed buffer.