From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keir Fraser <keir.fraser@eu.citrix.com>
Subject: Re: RE: [PATCH] rendezvous-based local time
	calibration WOW!
Date: Tue, 05 Aug 2008 22:43:00 +0100
Message-ID: <C4BE87F4.1BD61%keir.fraser@eu.citrix.com>
References: <20080805152755062.00000008444@djm-pc>
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To: "dan.magenheimer@oracle.com" <dan.magenheimer@oracle.com>, John Levon <levon@movementarian.org>
Cc: Ian Pratt <Ian.Pratt@eu.citrix.com>, "Xen-Devel (E-mail)" <xen-devel@lists.xensource.com>, Dave Winchell <dwinchell@virtualiron.com>
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On 5/8/08 22:27, "Dan Magenheimer" <dan.magenheimer@oracle.com> wrote:

>> No, as it would be incredibly slow on Solaris (I dread to imagine).
> 
> Could be.  On my box (Conroe), trapping tsc in an hvm is faster
> than reading pit or hpet in the hypervisor or in a native OS.

For a PV guest it only punts the monotonicity problem into the hypervisor of
course. You still need to access a shared counter, or use a lock (i.e.,
communication/synchronisation between processors), or be guaranteed that
local counters (TSCs) are driven by a common clock signal with negligible
skew.

 -- Keir