Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!uw-beaver!microsoft!w-colinp
From: w-colinp@microsoft.UUCP (Colin Plumb)
Newsgroups: comp.sys.transputer
Subject: Re: Low priority processes
Message-ID: <13@microsoft.UUCP>
Date: 28 Jan 89 06:13:19 GMT
References: <0000065B_000A71B4.0091F7D52D25ECC0$100_1@UK.AC.ABDN.BIOMED>
Reply-To: w-colinp@microsoft.uucp (Colin Plumb)
Organization: very little
Lines: 25

LOMAX@bio-medical-physics.aberdeen.ac.uk wrote:
>   Can anybody out there enlighten me as to how a single processor handles
> multiple processes waiting for communications. Do these waiting processes use
> any CPU time, and do they differ depending on whether they are waiting on hard
> or soft channels.

A process waiting for communication uses only memory, not CPU cycles.
Of course, copying the message (whether it's by a soft channel or DMA
from a link) does take memory cycles, and the latter can occur even if
the process isn't running.

Things that can take CPU resources away from a running process:
- The timer waking up a process
- A link communicating or finishing and waking up a process
- The event channel waking up a process
- Time-slicing at the low priority level
- For completeness, the reset pin has the obvious effects

Everything else is in response to some explicit action by the currently
running process.

I've had demos with 16000 processes runnning around.  If they were all
sleeping, I could have a quarter of a million.
-- 
	-Colin (uunet!microsof!w-colinp)