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. > > 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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