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Date: Fri, 6 May 2005 13:26:25 -0700
From: Kris Kennaway <kris@obsecurity.org>
To: Steve Ames <steve@energistic.com>
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cc: Kris Kennaway <kris@obsecurity.org>
Subject: Re: Benchmarking mpsafevfs with parallel tarball extraction
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On Fri, May 06, 2005 at 03:12:04PM -0500, Steve Ames wrote:
> On Fri, May 06, 2005 at 11:35:29AM -0700, Kris Kennaway wrote:
> > Kernel was built without INVARIANTS and other debugging options,
> > without ADAPTIVE_GIANT (which causes about a 200% performance penalty
> > on system time in my testing, and has marginal impact on real or user
> > time) and with 4BSD scheduler (ULE causes spontaneous reboots on this
> > machine).  The e4500 uses the esp SCSI controller, which runs
> > without Giant.
>=20
> I'm rather suprised that ADAPTIVE_GIANT causes so much performance
> degradation in your testing. On my, admittedly much more modest system,
> using ADAPTIVE_GIANT shaves about 6 minutes off a 'make world'. Haven't
> really done any research on why that is. I was just suprised by your
> 200% performance penalty.

Note: system time, not wall clock time.  It's probably because the
system is otherwise largely Giant-free (no hardware devices under
Giant, only things like ttys and CAM).  On systems with more Giant
usage in the I/O path you might see a benefit.

Kris

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