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From: conor@wren.inmos.co.uk (Conor O'Neill)
Newsgroups: comp.sys.transputer
Subject: Re: Monitoring CPU Load?
Message-ID: <12043@ganymede.inmos.co.uk>
Date: 23 Oct 90 13:33:05 GMT
References: <9801@discus.technion.ac.il> <1990Oct17.110318.9927@specialix.co.uk>
Sender: news@inmos.co.uk
Reply-To: conor@inmos.co.uk (Conor O'Neill)
Organization: INMOS Limited, Bristol, UK.
Lines: 76

>dario@techunix.BITNET (Dario Ringach) writes:
>
>
>>Is there any way to monitor the percent of usage of a
>>Transputer by running an OCCCAM process in PAR-rallel
>>with an application?  Thanks. -Dario

Here is an example OCCAM process which can be executed at high priority.
It wakes up periodically, and detects whether a low priority process
was executing (and therefore was interrupted).
It updates an 'idle count', which can be communicated to another process.

PROC monitor(CHAN OF BOOL req, CHAN OF INT data)

  VAL delay IS 1000 : -- 1 millisecond at high priority

  INT Wdesc.save :
  PLACE Wdesc.save AT 11 : -- address of saved low priority Wdesc
                           -- (see chapter 10.2 of the Compiler Writer's Guide)

  BOOL running :
  INT idle :
  SEQ
    idle := 0
    running := TRUE
    WHILE running
      TIMER time :
      INT now :
      SEQ
        time ? now
        PRI ALT
          BOOL request :
          req ? request
            IF
              request  -- if request is TRUE, return and reset the idle count
                SEQ
                  data ! idle
                  idle := 0
              TRUE     -- if request is FALSE, shutdown
                running := FALSE
          time ? AFTER now PLUS delay
            IF
              Wdesc.save = ((MOSTNEG INT) + 1) -- '1' means low priority
                idle := idle PLUS 1 -- make sure it can't overflow
              TRUE
                SKIP -- there was a low priority process executing
:

Sending TRUE down 'req' will return the idle count down 'data', and
reset the count. Sending FALSE will terminate the process.

The process would be used somewhat like this:

CHAN OF BOOL req  :
CHAN OF INT  data :
PRI PAR
  monitor(req, data)
  INT idle :
  SEQ
    ...  your program here
    req ! TRUE
    data ? idle
    ...  display the idle count, or whatever
    req ! FALSE


Note that the 'granularity' of the idle count can be adjusted by changing
the delay. While waiting on the timer queue, no CPU time is used, so the
only overhead is the cost of the loop every millisecond.
Note too that this process does not take other high priority processes
into account.

---
Conor O'Neill, Software Group, INMOS Ltd., UK.
UK: conor@inmos.co.uk		US: conor@inmos.com
"It's state-of-the-art" "But it doesn't work!" "That is the state-of-the-art".