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RE: [Xen-devel] No noht?

To: "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx>, "Xen-Devel (E-mail)" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] No noht?
From: "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx>
Date: Mon, 21 Apr 2008 19:47:52 -0600
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> but noone has yet complained.

Perhaps that's because the common use case is "try
noht and see if it makes any difference".  Guess what?
Since "noht" is silently ignored, it *doesn't* make any
difference. ;-) There are many xen-devel and xen-users
postings (since it disappeared) that indicate that noht
is assumed to work.  Even Mark Williamson has a 2007
posting that implies that it should work.

Also, I'll bet the fraction of machines running Xen
today that both support hyperthreading (and have it
turned on in the BIOS) is very small.  But
if rumors are true, that may change over the
next couple of years.

Any comments or concerns from CPU vendors?

> -----Original Message-----
> From: Keir Fraser [mailto:keir.fraser@xxxxxxxxxxxxx]
> Sent: Monday, April 21, 2008 4:54 PM
> To: dan.magenheimer@xxxxxxxxxx; Xen-Devel (E-mail)
> Subject: Re: [Xen-devel] No noht?
> It disappeared a long time ago, possibly by accident, but 
> noone has yet
> complained.
>  -- Keir
> On 21/4/08 22:42, "Dan Magenheimer" 
> <dan.magenheimer@xxxxxxxxxx> wrote:
> > Am I correct in reading the code that there is no "noht"
> > (turn off hyperthreading) option in Xen (except in powerpc)?
> > This was a surprise to me as I've seen it documented in
> > various places and I recently suggested it as a diagnostic
> > to a customer.
> >
> > ===================================
> > If Xen could save time in a bottle / then clocks wouldn't 
> virtually skew /
> > It would save every tick / for VMs that aren't quick /
> > and Xen then would send them anew
> > (with apologies to the late great Jim Croce)
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel

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