Date: Thu, 27 Sep 2012 15:39:39 +0200 From: Frerich Raabe <raabe@froglogic.com> To: freebsd-doc@freebsd.org Subject: Relevance of kern.hz with FreeBSD 9 being a Guest OS Message-ID: <5064571B.3030203@froglogic.com>
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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
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