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    Command:

    cytune

    
    
    

    SYNOPSIS

           cytune [options] tty [...]
    
    
    

    DESCRIPTION

           cytune queries and modifies the interruption threshold for the Cyclades
           driver.  Each serial line on a Cyclades card has  a  12-byte  FIFO  for
           input (and another 12-byte FIFO for output).  The "threshold" specifies
           how many input characters must be present in the FIFO before an  inter-
           ruption  is  raised.   When a Cyclades tty is opened, this threshold is
           set to a default value based on baud rate:
    
                  Baud        Threshold
    
                  50-4800            10
                  9600                8
                  19200               4
                  38400               2
                  57600-150000        1
    
           If the threshold is set too low, the large number of interruptions  can
           load  the  machine  and  decrease  overall  system  throughput.  If the
           threshold is set too high, the FIFO buffer can overflow, and characters
           will  be  lost.  Slower machines, however, may not be able to deal with
           the interrupt load, and will require that  the  threshold  be  adjusted
           upwards.
    
           If the cyclades driver was compiled with ENABLE_MONITORING defined, the
           cytune command can be used with the -q option to report interrupts over
           the  monitoring interval and characters transferred over the monitoring
           interval.  It will also report the state of the FIFO.  The maximum num-
           ber of characters in the FIFO when an interrupt occurred, the instanta-
           neous count of characters in the FIFO, and how many characters are  now
           in the FIFO are reported.  This output might look like this:
    
                  /dev/cubC0: 830 ints, 9130 chars; fifo: 11 threshold, 11 max, 11
                  now
                     166.259866 interrupts/second, 1828.858521 characters/second
    
           This output indicates that for this monitoring period,  the  interrupts
           were  always being handled within one character time, because max never
           rose above threshold.  This is good, and you can probably run this way,
           provided  that  a  large number of samples come out this way.  You will
           lose characters if you overrun the FIFO, as the Cyclades hardware  does
           not  seem  to support the RTS RS-232 signal line for hardware flow con-
           trol from the DCE to the DTE.
    
           In query mode cytune will produce a summary report when  ended  with  a
           SIGINT or when the threshold or timeout is changed.
    
           There  may  be  a responsiveness vs. throughput tradeoff.  The Cyclades
           card, at the higher speeds, is capable of putting a very high interrupt
           load  on the system.  This will reduce the amount of CPU time available
    
    
    

    OPTIONS

           -s, --set-threshold value
                  Set the current threshold to value characters.  Note that if the
                  tty is not being held open by  another  process,  the  threshold
                  will  be  reset on the next open.  Only values between 1 and 12,
                  inclusive, are permitted.
    
           -t, --set-flush value
                  Set the current flush timeout to value units.  Note that if  the
                  tty  is  not  being  held open by another process, the threshold
                  will be reset on the next open.  Only values between 0 and  255,
                  inclusive,  are  permitted.   Setting  value  to zero forces the
                  default, currently 0x20 (160ms), but soon  to  be  0x02  (10ms).
                  Units are 5 ms.
    
           -g, --get-threshold
                  Get the current threshold and timeout.
    
           -S, --set-default-threshold value
                  Set  the default threshold to value characters.  When the tty is
                  next opened, this value will be used  instead  of  the  default.
                  Only values between 1 and 12, inclusive, are permitted.
    
           -T, --set-default-flush value
                  Set  the  default flush timeout to value units.  When the tty is
                  next opened, this value will be used instead of the default.  If
                  value is zero, then the value will default to 0x20 (160ms), soon
                  to be 0x02 (10ms).
    
           -G, --get-glush
                  Get the default threshold and flush timeout values.
    
           -q, --stats
                  Gather statistics about the tty.  The results are only valid  if
                  the  Cyclades  driver  has  been compiled with ENABLE_MONITORING
                  defined.  This is probably not the default.
    
           -i, --interval interval
                  Statistics will be gathered every interval seconds.
    
    
    

    BUGS

           If you run two copies of cytune at the same time to  report  statistics
           about the same port, the 'ints', 'chars', and 'max' value will be reset
           and not reported correctly.  cytune should prevent this, but does  not.
    
    
    

    FILES

           /dev/ttyC[0-8]
           /dev/cubC[0-8]
    
    
    

    SEE ALSO

    
    
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