Re: [Qemu-devel] time inside qemu

[Marius Monton]

That's true, and I don't care about it. I'd like to get a method to stop/start time inside qemu in order to simulate execution of large pieces of hw out of qemu (look at qemu-systemc project).
If qemu is freeze  meanwhile a systemc simulation is in progress (simulating a HW device of system), time should be freeze also.
In this way, execution time of a program inside qemu should appear shorter when using accelerator HW than only SW application. I know these times are not reals, but it should be enough to estimate correctness and execution time on real platforms.

Does a way to stop/start time inside qemu?

Thanks,

Màrius

En/na Paul Brook ha escrit:

On Friday 29 December 2006 17:53, Màrius Montón wrote:
  

Hi,

As I understand, OSes running inside qemu "have" notion of time: (its
date and time works, time(1) command works, etc.).
My question is about how qemu manages time. I need to stop and start
again this "virtual-time".
    

qemu doesn't maintain virtual time, it just uses the real host time.

  

I just tried with cpu_disable_ticks() and cpu_enable_ticks(). It seems
to work partially: at least now system date and time are out of sync..
    

I suspect you'll find that for anything other than very coarse user (ie. user 
stop/continue) these are effectively useless.

Any benchmark/performance measurements you make inside qemu are meaningless. 
qemu performance bears no relation whatsoever to the performance 
characteristics of real hardware.

  

Paul


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Màrius Montón i Macián   address@hidden   http://cephis.uab.es Hardware Engineer CEPHIS Centre de Prototips i Solucions Hardware-Software Dep. Microelectrònica i Sistemes Electrònics ETSE - Universitat Autònoma de Barcelona (UAB)

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