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Date: Thu, 27 Sep 2012 15:39:39 +0200
From: Frerich Raabe <raabe@froglogic.com>
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Subject: Relevance of kern.hz  with FreeBSD 9 being a Guest OS
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Hi,

section 23.2.1.2 ("Configuring FreeBSD on Mac OS/X Parallels") of the 
FreeBSD Handbook explains:

   The most important step is to reduce the kern.hz tunable to reduce 
the CPU utilization of FreeBSD [..] Without this setting, an idle 
FreeBSD Parallels guest OS will use roughly 15% of the CPU of a single 
processor iMAC.

I assume the reasoning is that a high kern.hz setting makes the VM host 
software spend too much time on handling timer interrupts.

However, in FreeBSD 9, the "dynamic tick mode" (AKA "tickless mode") is 
the default, controlled by the "kern.eventtimer.periodic" setting which 
defaults to 0 (i.e. tickless mode). This makes me wonder: does the above 
mentioned part of the manual still have any relevance for FreeBSD 9.0 
and newer?

-- 
Frerich Raabe - raabe@froglogic.com
www.froglogic.com - Multi-Platform GUI Testing