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From: trt@mcnc.org (Tom Truscott)
Newsgroups: comp.arch
Subject: Re: IBM RS6000
Summary: pipelines seem quite fast on RS/6000
Message-ID: <7535@alvin.mcnc.org>
Date: 11 Jan 91 19:37:57 GMT
References: <1991Jan10.214122.9506@news.arc.nasa.gov> <3117@crdos1.crd.ge.COM>
Organization: MCNC; RTP, NC
Lines: 36

>   I've heard the same thing about context switching. I won't get to
> benchmark a system until February, so I can't be sure, but I was shown
> figures which indicated that running processes using temp files was
> faster than pipes.

In the following test (of AIX 3.1 on low-end RS/6000),
pipelines seemed as fast as temporary files:

}  $ cat x
}  soelim /usr/dict/words > tmp1
}  eqn < tmp1 > tmp2
}  tbl < tmp2 > tmp3
}  nroff < tmp3 > /dev/null
}  rm tmp1 tmp2 tmp3
}  $ time sh x
}  
}  real    0m17.24s
}  user    0m16.11s
}  sys     0m0.39s
}  
}  
}  $ cat y
}  soelim /usr/dict/words | eqn | tbl | nroff > /dev/null
}  $ time sh y
}  
}  real    0m16.49s
}  user    0m16.10s
}  sys     0m0.35s
}  $ ^D

An interesting detail of RS/6000 pipelines is that they hold 32k.
That means pipelines such as
	(cd $1 && tar cf - .) | (cd $2 && tar xpf -)
should need far fewer context switches
than are needed on systems with only a 4k pipeline buffer.
	Tom Truscott