Re: [Xen-devel] write_tsc in a PV domain?

To:	Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject:	Re: [Xen-devel] write_tsc in a PV domain?
From:	Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date:	Tue, 01 Sep 2009 08:16:49 +0100
Cc:	"Xen-Devel \(E-mail\)" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
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On 31/08/2009 22:06, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

> A thousand cycles to trap, decode, call get_s_time,
> and return seems astoundingly good?  Probably it's
> faster than a vmexit because there's so much less state
> to save.  But still it's 15x slower than a raw rdtsc.

A kernel trap used to take about a microsecond. Maybe it has got faster on
new processors.

 -- Keir

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Re: [Xen-devel] write_tsc in a PV domain?