From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeremy Fitzhardinge <jeremy@goop.org>
Subject: Re: [RFC] Correct/fast timestamping in apps under Xen
	[1	of 4]: Reliable TSC
Date: Fri, 09 Oct 2009 22:55:01 -0700
Message-ID: <4AD021B5.5070806@goop.org>
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To: Dan Magenheimer <dan.magenheimer@oracle.com>
Cc: kurt.hackel@oracle.com, Ian Pratt <Ian.Pratt@eu.citrix.com>, "Xen-Devel (E-mail)" <xen-devel@lists.xensource.com>, Tim Deegan <Tim.Deegan@citrix.com>, Keir Fraser <Keir.Fraser@eu.citrix.com>
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On 10/09/09 19:36, Dan Magenheimer wrote:
> Very nice!
>
> One more measurement if you haven't already torn down
> your test environment:   If you are at xen-unstable tip,
> with tsc emulation on, please try something like:
>
> for i in {0..100}; do
> xm debug-key s; xm dmesg | tail; sleep 1;
> done
>
> to get an idea of the number of rdtsc's being
> done per second (and also divide by the number
> of cores so we have rdtsc's/sec/core).  This is
> of course unloaded, so if you have a favorite
> load to throw on it, that would be very interesting
> also.
>   

The kernel does about between 400k and 1.4M/sec, median around ~600k,
for a git pull (which I think is single-threaded), and about
200k-500k/sec for a kernel compile (-j4 on 2 vcpus).  Usermode is a much
lower rate; around 1000/sec for the kernel compile.

Baseline idle is around 1000/sec kernel, 10/sec user.

Also, my inline naked rdtsc benchmark shows that the emulated rdtsc is
taking around 465ns (vs 30, a 15x slowdown).

    J