• Julian Wiedmann's avatar
    s390/qdio: reduce SLSB writes during Input Queue processing · a87ee116
    Julian Wiedmann authored
    Streamline the processing of QDIO Input Queues, and remove some
    intermittent SLSB updates (no deleting of old ACKs, no redundant
    transitions through NOT_INIT).
    
    Rather than counting ACKs, we now keep track of the whole batch of
    SBALs that were completed during the current polling cycle.
    Most completed SBALs stay in their initial state (ie. PRIMED or ERROR),
    except that the most recent SBAL in each sub-run is ACKed for
    IRQ reduction.
    
    The only logic changes happen in inbound_handle_work(), the other
    delta is just a renaming of the variables that track the SBAL batch.
    
    Note that in particular we don't need to flip the _oldest_ SBAL to
    an idle state (eg. NOT_INIT or ACKed) as a guard against catching our
    own tail. Since get_inbound_buffer_frontier() will never scan more than
    the remaining nr_buf_used SBALs, this scenario just doesn't occur.
    Signed-off-by: default avatarJulian Wiedmann <jwi@linux.ibm.com>
    Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
    a87ee116
qdio_debug.c 8.39 KB