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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.

Thomas [Page 1]  RFC 546 TENEX Load Averages for July 1973 10 August 1973

 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
    machine.

 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.]

Thomas [Page 2]  RFC 546 TENEX Load Averages for July 1973 10 August 1973

     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)

Thomas [Page 3]  RFC 546 TENEX Load Averages for July 1973 10 August 1973

Endnotes

 [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 ]

Thomas [Page 4]