sys-utils/cytune.8

   1 .\" cytune.8 --
   2 .\" Created: Sat Mar  4 17:44:53 1995 by faith@cs.unc.edu
   3 .\" Update: Sat Mar  4 18:22:24 1995 by faith@cs.unc.edu
   4 .\" Update: Sun Mar  5 06:40:12 1995 by njs@scifi.emi.net
   5 .\" Copyright 1995 Rickard E. Faith (faith@cs.unc.edu)
   6 .\"
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  27 .TH CYTUNE 8 " 4 Mar 1995" "" "Linux Programmer's Manual"
  28 .SH NAME
  29 cytune \- Tune Cyclades driver parameters
  30 .SH SYNOPSIS
  31 .BI "cytune [-q [-i " interval "]] ([-s " value "]|[-S " value "]) [-g|G] "
  32 .BI ([-t " timeout" ]|[-T " timeout" ]) " tty" " [" tty " ...]"
  33 .SH DESCRIPTION
  34 .B cytune
  35 queries and modifies the interruption threshold for the Cyclades driver.
  36 Each serial line on a Cyclades card has a 12-byte FIFO for input (and
  37 another 12-byte FIFO for output).  The "threshold" specifies how many input
  38 characters must be present in the FIFO before an interruption is raised.
  39 When a Cyclades tty is opened, this threshold is set to a default value
  40 based on baud rate:
  41 .sp
  42 .RS
  43     Baud        Threshold
  44 .sp
  45 50-4800            10
  46 .br
  47 9600                8
  48 .br
  49 19200               4
  50 .br
  51 38400               2
  52 .br
  53 57600-150000        1
  54 .RE
  55 .PP
  56 If the threshold is set too low, the large number of interruptions can load
  57 the machine and decrease overall system throughput.  If the threshold is set too high, the
  58 FIFO buffer can overflow, and characters will be lost.  Slower machines,
  59 however, may not be able to deal with the interrupt load, and will require
  60 that the threshold be adjusted upwards.
  61 .PP
  62 If the cyclades driver was compiled with
  63 .B ENABLE_MONITORING
  64 defined, the cytune command can be used with the
  65 .B \-q
  66 option to report interrupts over the monitoring interval and
  67 characters transferred over the monitoring interval.  It will also report
  68 the state of the FIFO.  The maximum number of characters in the FIFO when
  69 an interrupt occurred, the instantaneous count of characters in the FIFO,
  70 and how many characters are now in the FIFO are reported.  This output might
  71 look like this:
  72 .sp
  73 .RS
  74 /dev/cubC0: 830 ints, 9130 chars; fifo: 11 threshold, 11 max, 11 now
  75 .br
  76    166.259866 interrupts/second, 1828.858521 characters/second
  77 .RE
  78 .PP
  79 This output indicates that for this monitoring period, the interrupts were
  80 always being handled within one character time, because
  81 .B max
  82 never rose above
  83 .BR threshold .
  84 This is good, and you can probably run this way, provided that a large
  85 number of samples come out this way.  You will lose characters if you
  86 overrun the FIFO, as the Cyclades hardware does not seem to support
  87 the RTS RS-232 signal line for hardware flow control from the
  88 DCE to the DTE.
  89 .PP
  90 In query mode
  91 .B cytune
  92 will produce a summary report when ended with
  93 a SIGINT or when the threshold or timeout is changed.
  94 .PP
  95 There may be a responsiveness vs. throughput tradeoff.  The Cyclades card,
  96 at the higher speeds, is capable of putting a very high interrupt load on the
  97 system.  This will reduce the amount of CPU time available for other tasks
  98 on your system.  However, the time it takes to respond to a single character
  99 may be increased if you increase the threshold.  This might be noticed by
 100 monitoring
 101 .BR ping (8)
 102 times on a SLIP link controlled by a Cyclades card.  If your SLIP link is
 103 generally used for interactive work such as
 104 .BR telnet (1),
 105 you may want to leave the threshold low, so that characters are responded
 106 to as quickly as possible.  If your SLIP link is generally used for file
 107 transfer, WWW, and the like, setting the FIFO to a high value is likely to
 108 reduce the load on your system while not significantly affecting
 109 throughput.  Alternatively, see the
 110 .B \-t
 111 or
 112 .B \-T
 113 options to adjust the time that the cyclades waits before flushing its
 114 buffer.  Units are 5ms.
 115 .PP
 116 If you are running a mouse on a Cyclades port, it is likely that you would
 117 want to maintain the threshold and timeout at a low value.
 118 .PP
 119 .SH OPTIONS
 120 .TP
 121 .BI \-s " value"
 122 Set the current threshold to
 123 .I value
 124 characters.  Note that if the
 125 .I tty
 126 is not being held open by another process, the threshold will be reset on
 127 the next open.  Only values between 1 and 12, inclusive, are permitted.
 128 .TP
 129 .BI \-t " value"
 130 Set the current flush timeout to
 131 .I value
 132 units.  Note that if the
 133 .I tty
 134 is not being held open by another process, the threshold will be reset on
 135 the next open.  Only values between 0 and 255, inclusive, are permitted.
 136 Setting
 137 .I value
 138 to zero forces the default, currently 0x20 (160ms), but soon to be 0x02
 139 (10ms).  Units are 5 ms.
 140 .TP
 141 .B \-g
 142 Get the current threshold and timeout.
 143 .TP
 144 .BI \-T " value"
 145 Set the default flush timeout to
 146 .I value
 147 units.  When the
 148 .I tty
 149 is next opened, this value will be used instead of the default.  If
 150 .I value
 151 is zero, then the the value will default to 0x20 (160ms), soon to be 0x02
 152 (10ms).
 153 .TP
 154 .B \-G
 155 Get the default threshold and flush timeout values.
 156 .TP
 157 .B \-q
 158 Gather statistics about the
 159 .IR tty .
 160 The results are only valid if the Cyclades driver has been compiled with
 161 .B ENABLE_MONITORING
 162 defined.  This is probably not the default.
 163 .TP
 164 .BI \-i " interval"
 165 Statistics will be gathered every
 166 .I interval
 167 seconds.
 168 .SH BUGS
 169 If you run two copies of
 170 .B cytune
 171 at the same time to report statistics about the same port,
 172 the 'ints', 'chars', and 'max' value will be reset
 173 and not reported correctly.
 174 .B cytune
 175 should prevent this, but does not.
 176 .\" .SH AUTHOR
 177 .\" Nick Simicich (njs@scifi.emi.net), with modifications by
 178 .\" Rik Faith (faith@cs.unc.edu)
 179 .SH FILES
 180 .I /dev/ttyC[0-8]
 181 .br
 182 .I /dev/cubC[0-8]
 183 .SH "SEE ALSO"
 184 .BR setserial (8)
 185 .SH AVAILABILITY
 186 The cytune command is part of the util-linux-ng package and is available from
 187 ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.