From: "Jim C. Brown" <jma5@umd.edu>
To: a_mulyadi@softhome.net, qemu-devel@nongnu.org
Subject: Re: Re: [Qemu-devel] Timing problems
Date: Sun, 28 Aug 2005 23:21:52 -0400 [thread overview]
Message-ID: <20050829032152.GA26595@jbrown.mylinuxbox.org> (raw)
In-Reply-To: <200508291001.39221.a_mulyadi@softhome.net>
On Mon, Aug 29, 2005 at 10:01:39AM +0700, Mulyadi Santosa wrote:
> Hello...
>
> > It simply
> > replaces the virtual timer mechanism based on CPU tick count (which
> > is totally messed up in a SpeedStep setting) with calls to the
> > realtime clock. It should work even when emulation is stopped
> > intermittently, I hope, since the built in "virtual clock stop"
> > mechanism ist left unchanged.
>
> Hm..... hard choice.....correctness traded for perfomance.... But
> anyway....IMHO this hack is needed for every speed-step enabled
> machine. Perhaps...the other workaround is via cpufreqd? I don't have
> any Pentium M based PC/laptop around, so this is just a pure guess
>
The other patch for this just used a constant to increment the time iirc
(based on some value in /proc).
> BTW, your patch seems reversed....if you really mean you want to fetch
> realtime clock, you should use "rdtsc", right? But the patch seems
> replaced "rdtsc" with get_clock()....
>
The values returned by rdtsc seem to vary depending on cpu frequency when
speedstep is enabled. get_clock() is actually more accurate (tho i think less
precise), at least from the user land POV.
--
Infinite complexity begets infinite beauty.
Infinite precision begets infinite perfection.
next prev parent reply other threads:[~2005-08-29 3:43 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-08-28 19:23 [Qemu-devel] Timing problems Sven Zenker
2005-08-29 3:01 ` Mulyadi Santosa
2005-08-29 3:21 ` Jim C. Brown [this message]
2005-08-30 21:08 ` Sven Zenker
2005-08-31 12:19 ` Mulyadi Santosa
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