Date: Mon, 12 Feb 2001 15:43:39 -0800 (PST) From: Matt Dillon <dillon@earth.backplane.com> To: Dag-Erling Smorgrav <des@ofug.org> Cc: Greg Lehey <grog@lemis.com>, Danny Braniss <danny@cs.huji.ac.il>, freebsd-hackers@FreeBSD.ORG Subject: Re: soft updates performance Message-ID: <200102122343.f1CNhd053320@earth.backplane.com> References: <E14RurO-0000Zl-00@cs.huji.ac.il> <xzp7l2wc6v6.fsf@flood.ping.uio.no> <20010213095300.D2178@wantadilla.lemis.com> <xzp3ddjpjlk.fsf@flood.ping.uio.no>
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:> In fact, it's exactly the opposite. 'make world' is CPU-bound, so the
:> speed of the I/O system is irrelevant. If it were I/O bound, soft
:> updates *would* make a difference, because a number of unnecessary
:> writes would be eliminated.
:
:Read what he writes. Soft updates *did* make a difference - they
:shaved ~30% off his worldstone. It's parallelization that doesn't make
:a difference in his case, because his CPU and FSB are fast enough that
:the I/O system is left completely in the dust. This is a 900 MHz box,
:probably with a 100 MHz or 133 MHz FSB, not the old 486DX33 you have
:lying in a corner.
:
:DES
:--
:Dag-Erling Smorgrav - des@ofug.org
A suspect a good chunk of that is not using -pipe. I would be
interested in buildworld numbers with -pipe vs with -pipe + softupdates.
Without -pipe softupdates will make a huge difference due to temporary
file creation & deletion.
When Kirk first tested softupdates against buildworld, he explicitly
tested it with and without -pipe and found that much of the performance
benefit (for buildworld) occured when not using -pipe.
-Matt
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