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From: Chris Lalancette <clalance@redhat.com>
To: Keir Fraser <keir.fraser@eu.citrix.com>
Cc: "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
Subject: Re: vgettimeofday disabled?
Date: Wed, 03 Sep 2008 18:02:06 +0200	[thread overview]
Message-ID: <48BEB4FE.3000900@redhat.com> (raw)
In-Reply-To: <C4E4734D.26B55%keir.fraser@eu.citrix.com>

Keir Fraser wrote:
> We probably don't update vxtime structure, so you likely get dodgy results
> from do_vgettimedofday(). However, forcing vxtime to track vcpu0's time info
> obtained from Xen would probably be quite easy to do and may be accurate
> enough.
> 
> But, without that extra engineering, I recommend you check what answers
> you're getting from gettimeofday(). Could be quite a significant
> performance/correctness tradeoff ;-)

Ah, OK.  So there's not really a fundamental issue (which I was worried about),
more just it hasn't been implemented all the way.  Interestingly, it doesn't
seem to be explicitly disabled in the LKML pv_ops implementation, so either it's
being updated properly there, or time is *way* off.

Thanks for the info.

Chris Lalancette

      reply	other threads:[~2008-09-03 16:02 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-09-03 15:48 vgettimeofday disabled? Chris Lalancette
2008-09-03 16:01 ` Keir Fraser
2008-09-03 16:02   ` Chris Lalancette [this message]

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