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From: raveling@isi.edu (Paul Raveling)
Newsgroups: comp.os.mach
Subject: Re: Mach context switch time
Message-ID: <10159@venera.isi.edu>
Date: 16 Oct 89 23:26:47 GMT
References: <2895@netcom.UUCP>
Sender: news@venera.isi.edu
Reply-To: raveling@isi.edu (Paul Raveling)
Organization: USC Information Sciences Institute
Lines: 23

In article <2895@netcom.UUCP>, hue@netcom.UUCP (Jonathan Hue) writes:
> 
> >        Mean real time per context switch, corresponding context
switch rate:
> >        NeXt            MACH              873           1,145
> 
> The following program executes the loop 10000 times in 7.3 seconds on a
> NeXT.  Each time through the loop is 2 context switches, so this works
> out to 2740 context switches/sec, or 365us per context switch.

	This is suggests i/o system overhead for the short
	(10-byte) piped messages that pt uses is about 500
	microseconds.

	BTW, someone else ran the pt benchmark on a NeXt machine
	and reported 920 microseconds per (context switch + msg
	transmission).  Timing may vary a bit among individual
	machines.


----------------
Paul Raveling
Raveling@isi.edu