[Qemu-devel] time synchronization with qemu

[Qemu-devel] time synchronization with qemu

[giovanni bracco]

I have tried to use qemu to emulate a cluster of 3 linux boxes used as AFS 
cell server system (RH 8.0 in my case) on a  SUSE 9.1 host system.
More o less it works but I have a problem with the time synchronization of the 
3 boxes. 
AFS deamons require that the 3 servers have the same time but I have not found 
a reasonable strategy to obtain that reliably.
Any suggestion?

Is there a way in which the emulated system inside qemu can keep the time of 
the host system?

Thank you

Giovanni

-- 
Giovanni Bracco
ENEA INFO 
(Servizio Informatica e Reti)
Via E. Fermi 45
I-00044 Frascati (Roma) Italy
phone 00-39-06-9400-5597
FAX   00-39-06-9400-5735
E-mail  bracco@frascati.enea.it
WWW http://fusfis.frascati.enea.it/~bracco

[Qemu-devel] QEMU Linux x86 user space emulator invocation under osx

[Bernard Sauterel]

Dear all

I use Mac OS X 10.3, and want to run a linux x86 binary without the
need of a hard drive image file.

I look at QEMU documentation, chapter 5, and I believe it describe
what I want, before previously on the docs I understood that this is
only possible with a linux host (and not a osx host like me).

Am I right ? And if yes, is any alpha-beta-trick stage project which
allow it under osx ? Or any clue ?

Best regards

Bernard Sauterel

Re: [Qemu-devel] QEMU Linux x86 user space emulator invocation under osx

[Pablo Bendersky]

You are right. The linux-user mode is only available on a Linux host
for the moment.

On Tue, 31 Aug 2004 15:07:23 +0200, Bernard Sauterel
<bernard@hubrisys.com> wrote:
> Dear all
> 
> I use Mac OS X 10.3, and want to run a linux x86 binary without the
> need of a hard drive image file.
> 
> I look at QEMU documentation, chapter 5, and I believe it describe
> what I want, before previously on the docs I understood that this is
> only possible with a linux host (and not a osx host like me).
> 
> Am I right ? And if yes, is any alpha-beta-trick stage project which
> allow it under osx ? Or any clue ?
> 
> Best regards
> 
> Bernard Sauterel
> 
> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
> http://lists.nongnu.org/mailman/listinfo/qemu-devel
>

Re: [Qemu-devel] QEMU Linux x86 user space emulator invocation under osx

[Mark Williamson]

Darwine <http://darwine.opendarwin.org> is aiming to do this for windows apps. 
- it's in development and not ready for production use yet.

In order to run Linux apps on MacOS X, the emulation layer would have to 
translate system calls, etc. to Darwin calls, whereas for x86 Linux on 
(something else) Linux, the system calls themselves are the same.

In this interview <http://www.osviews.com/modules.php?op=modload&name=News&file
=article&sid=2046>, Jim White says he's interested in Linux emulation on Macos 
X.  There was a discussion on this mailing list a few weeks ago about Darwine 
where Linux emulation got mentioned -  you might also want to check out.

HTH,
Mark

Re: [Qemu-devel] time synchronization with qemu

[Gianni Tedesco]

On Tue, 2004-08-31 at 14:21 +0200, giovanni bracco wrote:
> I have tried to use qemu to emulate a cluster of 3 linux boxes used as AFS 
> cell server system (RH 8.0 in my case) on a  SUSE 9.1 host system.
> More o less it works but I have a problem with the time synchronization of the 
> 3 boxes. 
> AFS deamons require that the 3 servers have the same time but I have not found 
> a reasonable strategy to obtain that reliably.
> Any suggestion?
> 
> Is there a way in which the emulated system inside qemu can keep the time of 
> the host system?

The same way you do it with real computers....

Usually that means NTP or something.

-- 
// Gianni Tedesco (gianni at scaramanga dot co dot uk)
lynx --source www.scaramanga.co.uk/scaramanga.asc | gpg --import
8646BE7D: 6D9F 2287 870E A2C9 8F60 3A3C 91B5 7669 8646 BE7D

Re: [Qemu-devel] time synchronization with qemu

[giovanni bracco]

On Tuesday 14 September 2004 17:28, Gianni Tedesco wrote:
> On Tue, 2004-08-31 at 14:21 +0200, giovanni bracco wrote:
> > I have tried to use qemu to emulate a cluster of 3 linux boxes used as
> > AFS cell server system (RH 8.0 in my case) on a  SUSE 9.1 host system.
> > More o less it works but I have a problem with the time synchronization
> > of the 3 boxes.
> > AFS deamons require that the 3 servers have the same time but I have not
> > found a reasonable strategy to obtain that reliably.
> > Any suggestion?
> >
> > Is there a way in which the emulated system inside qemu can keep the time
> > of the host system?
>
> The same way you do it with real computers....
>
> Usually that means NTP or something.

I have tried but it does not works well and  I think that the reason is that 
inside a qemu system the clock is not stable and depends on the load of the 
host machine (which depends, in my case of the 3 qemu running together, also 
on the load on the other qemu systems). I suppose that ntp does not work well 
with very unstable clocks!

Up  to now the best solution I have found is to run a cron job on the host 
which sets every minute the clock of the 3 qemu systems using "rsh rdate -s 
host.ip" but still the time difference between qemu systems is til between 3 
and 10 seconds (even if there is a reset about every minute!)

Any suggestion is welll accepted!

Giovanni

ps:
on the host machine, kernel 2.6.5, I set at the boot the option clock=pit 
becouse otherwise the first qemu that I start runs a clock faster that the 
real clock of the host while the other two run slower. 
With clock=pit option all the three qemu run slower than the host and so the 
intrinsic time diffrence between them is lower.

-- 
Giovanni Bracco
ENEA INFO 
(Servizio Informatica e Reti)
Via E. Fermi 45
I-00044 Frascati (Roma) Italy
phone 00-39-06-9400-5597
FAX   00-39-06-9400-5735
E-mail  bracco@frascati.enea.it
WWW http://fusfis.frascati.enea.it/~bracco

Re: [Qemu-devel] time synchronization with qemu

[Piotr Krysik]

Hi!

When qemu is waiting to read data from your host 
disk, the clock may slow down. For start try to 
work on small images that fit in ram.

My guess is that your guest uses timer interrupt 
as time source and when there should be two or more 
interrupts while qemu is waiting for disk read 
to complete, only first interrupt will be delivered. 
The solution is to modify qemu source code to use 
asynchronous disk IO. A patch was send on this list 
a few months ago (search the list archive for AIO), 
but I didn't try (or even analyze it), so I cannot 
tell if it can help.


Regards,

Piotrek

--- giovanni bracco <bracco@frascati.enea.it> wrote:

> I have tried but it does not works well and  I 
> think that the reason is that inside a qemu system 
> the clock is not stable and depends on the load 
> of the ost machine (which depends, in my case of 
> the 3 qemu running together, also on the load on 
> the other qemu systems). I suppose that ntp does 
> not work well with very unstable clocks!
> 
> Up  to now the best solution I have found is to 
> run a cron job on the host which sets every minute 
> the clock of the 3 qemu systems using "rsh rdate 
> -s host.ip" but still the time difference between 
> qemu systems is til between 3 and 10 seconds (even 
> if there is a reset about every minute!)
> 
> Any suggestion is welll accepted!
> 
> Giovanni



		
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