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Date:      Sun, 14 Oct 2001 09:50:34 +0200 (CEST)
From:      Søren Schmidt <sos@freebsd.dk>
To:        mjacob@feral.com
Cc:        Jordan Hubbard <jkh@FreeBSD.ORG>, jrossiter@symantec.com, sos@FreeBSD.ORG, freebsd-hackers@FreeBSD.ORG
Subject:   Re: Severe I/O Problems
Message-ID:  <200110140750.f9E7oZi05487@freebsd.dk>
In-Reply-To: <Pine.BSF.4.21.0110131158120.1529-100000@beppo>

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It seems Matthew Jacob wrote:
> Just following up myself on this... with a drive on my PC164 Alpha, the
> realtime difference between two different checkouts of cvs src is interesting:
> 
> -------------
> 
> Script started on Sat Oct 13 10:07:07 2001
> farrago.feral.com > # this is with wc off
> farrago.feral.com > /usr/bin/time cvs -q -d /home/ncvs co src > LOG
>      2478.99 real       201.48 user      1046.87 sys
> farrago.feral.com > exit
> exit
> 
> Script done on Sat Oct 13 10:55:36 2001
> Script started on Sat Oct 13 11:04:06 2001
> farrago.feral.com > # this is with wc on
> farrago.feral.com >  /usr/bin/time cvs -q -d /home/ncvs co src > LOG
>      2866.82 real       199.92 user       988.24 sys
> farrago.feral.com > exit
> exit
> 
> Script done on Sat Oct 13 11:57:51 2001
> -------------
> 
> All parameters were not totally lab controlled, but pretty close. I'd call it
> significant enough that I'll leave WC off for this machine.

Well I tried something semilar here, CVS tree on one disk, then newfs and
cvs co src on another (both DTLA's on via686b if that matters) to keep
things as equal as possible, singleuser mode of cause...

-SU: softupdates -wc writecache enabled -tags tagged queing enabled

res:		33.973u 19.425s 27:27.88 3.2%	583+7328k 47219+160828io 37pf+0w
res-SU:		33.552u 16.235s 9:53.49 8.3%	586+7244k 47180+864io 6pf+0w
res-wc:		32.959u 20.104s 3:38.23 24.3%	586+7317k 47232+160828io 37pf+0w
res-wc-SU:	33.343u 16.909s 2:52.81 29.0%	585+7269k 47184+863io 6pf+0w
res-wc-tags:	33.891u 29.705s 3:40.62 28.8%	587+7595k 47225+160548io 20pf+0w
res-wc-tags-SU:	33.946u 20.759s 2:48.97 32.3%	578+7234k 47183+863io 5pf+0w

That behaves more or less as I would expect...

It is worth nothing that there is close to an order of magnitude in
difference from the slowest to the fastest, and that WC is the single
option that can make that difference on its own...

-Søren

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