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Date: Sat, 3 Jun 1995 16:20:49 +1000
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199506030620.QAA04316@godzilla.zeta.org.au>
To: henrich@crh.cl.msu.edu, rls@kilroy.id.net
Subject: Re: A performance mystery
Cc: freebsd-hackers@FreeBSD.ORG, rgrimes@gndrsh.aac.dev.com
Sender: hackers-owner@FreeBSD.ORG
Precedence: bulk

>                Compaq Proliant 575             Micron P90 Powerstation

>time make       8:55                            9:39
>ram-speed       10.85 Mb/S, 7.08 Mb/S           10.61 Mb/S, 20.66 Mb/S
>iozone 200      2486434/4150208                 2446772/4203499
>iozone 16 8192  3360694/2677660                 2711469/13256071

>The make time is wall time, ram-speed tests the raw memory bandwidth, defeating
>cache almost 100%.  iozone 200 tests raw read/write performance to disk, as it
>far exceeds ram size, memory cache effect is insignificant.  iozone 16 8192
>tests the memory speed with cache involved, because the test size is so small,
>(as Rod pointed out) its essentially just a bunch of bcopy's.

>As you can see by the ram-speed and iozone tests (and the fact that its a
>Pentium-75!) the Compaq should be sorely beaten in build time over the Micron,
>but yet its not.  Hence the mystery.

Apparently the Compaq has a much better (memory) cache and it gets used a
lot for building the kernel.

Bruce