transputer scheduler

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2 total messages Started by David Suter Sat, 25 Mar 1989 06:45

#2584

Author: David Suter
Date: Sat, 25 Mar 1989 06:45

35 lines
2252 bytes

I have found little information about the implementation of concurrent processes
on a single transputer. At the hardware level the Transputer Ref. Manual makes
the point that the microcoded scheduler itself does not consume time
as inactive (read for i/o or suspended for a specified time) processes do not 
consume processor time. They are, it seems,  suspended
and placed on the active list only when an autonomous link interface (for i/o
- for timer in case of specified time?) cuases them to be rescheduled. 
A process is executed until it requests i/o or awaiting the timer.

This seems fine, however there is little information about how the OCCAM 
compiler maps its concurrent processes onto this. There is a brief statement
about PRIoritised processes - but what about equal priority processes. Does
the current implementation(s) of OCCAM time slice the equal priority
proceses (if so at what rate) or does it follow the above hardware model for
efficiency where
PAR
  process1
  process2
will actually run either as SEQ process1,process2 or visa versa
if neither requires i/o.
It seems hard to reason about efficiency of code without this info - can anyone
point me to a detailed account of this.
Also - what about the various C compilers - do any of them support 
multiprocessing on a single transputer - if so how?


---------------------
David Suter                            ISD: +61 3 479-2393
Department of Computer Science,        STD: (03) 479-2393
La Trobe University,                ACSnet: suter@latcs1.oz
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Re: transputer scheduler

#2588

Author: Pow Hwee Tan
Date: Sat, 01 Apr 1989 17:37

21 lines
846 bytes

About whether running a segment of code like

  PAR
    p1
    p2

will run sequentially or parallel on a SINGLE transputer, my experience
tells me that the transputer did do a time slice scheduling. This
is because if the above code were to run on a single transputer then
it will run slower than a sequential one, ie:

  SEQ
    p1
    p2

The slower performance is due to task switching.

pow-hwee tan
--
tph@minnie.cc.utexas.edu

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