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RFC 0546

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Tenex load averages for July 1973


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Network Working Group                                          B. Thomas
Request for Comments: 546                                      BBN-TENEX
NIC: 17792                                                10 August 1973

                   TENEX Load Averages for July 1973

   This RFC presents utilization data for the BBN and ISI TENEX systems
   which may be of interest to the network community.

   The graph on page 4 summarizes the load at the BBN-TENEX and USC-ISI
   Hosts during the work week for the month of July 1973.  The weekday
   hourly load average [1] for each site is plotted versus the time of
   day; the time of day is Eastern Daylight Time.

   Interpreting data such as this is tricky business.  However, it is
   difficult to resist making the following observations:

   1. The shapes of the BBN and ISI curves are approximately the same;
      furthermore, there is no skew between the curves.  This suggests
      that the user populations for the two systems have similar working
      habits and are acclimated to the same time zone.

   2. The significant features of both curves appear to be strongly
      correlated with "normal events" in the day of a user living on
      East Coast time,suggesting that the load at both sites is
      influenced most strongly by such users:

      a. the load begins to increase between 7-8 a.m. EDT as users begin
         their daily computing;

      b. it dips between 10-11 a.m. EDT (smoothed to a smaller rate of
         increase in the ISI curve) as users take their coffee break;

      c. the load peaks sharply between 1-2 p.m. EDT as users return
         from lunch to resume their computing;

      d. it decreases as the afternoon continues and as users go home
         from work;

      e. it reaches a local minimum between 6-7 p.m. EDT (minimum not
         present in ISI curve) when most people eat dinner;

      f. it increases to an evening peak between 9-10 p.m. EDT as some
         users come back from dinner and after dinner activities to
         resume their computing.

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   3. The curve for ISI is smoother than the one for BBN: the "coffee
      break" dip appears only as a decrease in slope; the dinner break
      and evening peak are completely smoothed  out.  This smoothing is
      probably due to the influence of the West Coast users of the ISI

   4.  During July the BBN system was more heavily loaded than the ISI
      system.  Since the data collected did not include the number of
      active jobs it is not possible to determine from the data whether
      BBN had more users or just more demanding users.

   The data presented on the graph is available as a side effect of the
   RSEXEC system.  The server programs for the RSEXEC system (RSSER
   programs) communicate regularly with one another exchanging status
   information.   The RSSER program at each site maintains a (dynamic)
   data base of the information it collects from the RSSER programs at
   other sites.  The NETLOAD command of the TENEX EXEC, as well as many
   RSEXEC commands, makes use of information in that database.

   The raw data for BBN and ISI [2] load curves (as well as data for the
   other TENEX sites that run RSSER) was collected by a program which
   creates daily load information files by periodically (every 3
   minutes) reading load average data from the data base maintained by
   RSSER.  The monthly summary was produced by a program that analyzes
   daily data files.

   [The following graph is also available in .PS and .PDF format.]

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       Weekday Hourly Load Averages
                                 July 1973
          ^                                        B  BBN-TENEX
          |                                        I  ISI-TENEX
       10 +
          |                            B
          +                              B
   Load   |
   Avg.   |                                B
          |                            I
          |                          *
          +                              I
          |                      B         I B
          |                        B
        5 +
          |                    B   I
          |                                  I
          +                      I
          |                  B
          +                                    I       B
          |                                    B
          |                                      I
          |                    I                   I B   B
          +                                          I
          |                  I                     B   I
          |                                      B
          |                B                             I B
          +  I             I                                 I
          |  B *                                             B
          |      * * I I *
          |          B B
          | 0-1 AM      6-7 AM     12-1 PM      6-7 PM      12
           (midnight)              (noon)            (midnight)
                    Time of Day (Eastern Daylight Time)

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   [1] The TENEX load average is a measure of CPU demand.  The load
   average is an average of the number of runable processes over a given
   time period.  For example, an hourly load average of 10 would mean
   that (for a single CPU system) at any time during that hour one could
   expect to see 1 process running and 9 others ready to run (i.e., not
   blocked for I/O) waiting for the CPU.

   [2] The data for BBN and ISI was chosen for presentation in this RFC
   because the BBN and ISI TENEXs are two of the major time-sharing
   service hosts on the network.

         [ This RFC was put into machine readable form for entry ]
            [ into the online RFC archives by Jim Larson 3/98 ]