RE: [Xen-devel] RE: [PATCH] rendezvous-based local time calibration WOW!

["Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx>]

> 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.

> -----Original Message-----
> From: John Levon [mailto:levon@xxxxxxxxxxxxxxxxx]
> Sent: Tuesday, August 05, 2008 3:13 PM
> To: Dan Magenheimer
> Cc: Ian Pratt; Xen-Devel (E-mail); Dave Winchell; Keir Fraser
> Subject: Re: [Xen-devel] RE: [PATCH] rendezvous-based local time
> calibration WOW!
> 
> 
> On Tue, Aug 05, 2008 at 02:49:25PM -0600, Dan Magenheimer wrote:
> 
> > The algorithm used to compute the timestamp information
> 
> Thanks.
> 
> > I'm not sure its possible to guarantee monotonicity in
> > PV domains (without a global lock) except by doing a trap
> > or hypercall at each "get time".
> 
> That's a shame.
> 
> > I've thought about implementing softtsc for PV domains for
> > this reason.  (Softtsc was just added at 4.0 for hvm domains
> > and causes all hvm tsc reads to trap.)  Would this be of
> > interest?
> 
> No, as it would be incredibly slow on Solaris (I dread to imagine).
> 
> regards,
> john
>


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