[Qemu-devel] Looking for ideas: Single process vs multi process qemu instances

[Qemu-devel] Looking for ideas: Single process vs multi process qemu instances

[Ajallooiean Hossein]

Hi All,


we are trying to do server simulation and for that purpose we need to have multiple Qemu instances (each can have a different spec) that are part of a virtual network (ns-3 in our case).


Now for the Qemu implementation part: would it be easier/better to have all the Qemu instances under a single process or multiple processes? i am assuming if one single process is used, there will be a threading conflict that would probably need to be looked at.


I am looking at this purely from a management/performance view.


Any ideas/suggestions?


Thanks

Hoss

Re: [Qemu-devel] Looking for ideas: Single process vs multi process qemu instances

[Alex Bennée]

Ajallooiean Hossein <hossein.ajallooiean@epfl.ch> writes:

> Hi All,
>
>
> we are trying to do server simulation and for that purpose we need to
> have multiple Qemu instances (each can have a different spec) that are
> part of a virtual network (ns-3 in our case).

So you are talking about using TCG for simulation rather than KVM here?

>
>
> Now for the Qemu implementation part: would it be easier/better to
> have all the Qemu instances under a single process or multiple
> processes? i am assuming if one single process is used, there will be
> a threading conflict that would probably need to be looked at.

QEMU isn't really setup for multiple machine instances in the one
binary. If you are simulating a complex set of communicating machines
then you will need one QEMU instance per machine.

TCG can now use multiple threads (one per emulated vCPU) but this has
only been enabled for a subset of architectures so far. You don't say
what architecture your servers machines are.

>
>
> I am looking at this purely from a management/performance view.
>
>
> Any ideas/suggestions?
>
>
> Thanks
>
> Hoss


--
Alex Bennée

Re: [Qemu-devel] Looking for ideas: Single process vs multi process qemu instances

[Ajallooiean Hossein]

Hi Alex,

Thanks for you email.

I'm on x86-64 and am emulating ARM64 using TCG - QEMU 2.9.

Well I was hoping to see if I can use a single process to have all the machines within it to do a simple lockstep execution among the emulating machines. 

Im assuming the biggest issue is the thread conflicts the machines would have? other than that do you see any other obstacles?

Thanks
Hoss

________________________________________
From: Alex Bennée <alex.bennee@linaro.org>
Sent: Thursday, June 22, 2017 11:45 AM
To: Ajallooiean Hossein
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] Looking for ideas: Single process vs multi process qemu instances

Ajallooiean Hossein <hossein.ajallooiean@epfl.ch> writes:

> Hi All,
>
>
> we are trying to do server simulation and for that purpose we need to
> have multiple Qemu instances (each can have a different spec) that are
> part of a virtual network (ns-3 in our case).

So you are talking about using TCG for simulation rather than KVM here?

>
>
> Now for the Qemu implementation part: would it be easier/better to
> have all the Qemu instances under a single process or multiple
> processes? i am assuming if one single process is used, there will be
> a threading conflict that would probably need to be looked at.

QEMU isn't really setup for multiple machine instances in the one
binary. If you are simulating a complex set of communicating machines
then you will need one QEMU instance per machine.

TCG can now use multiple threads (one per emulated vCPU) but this has
only been enabled for a subset of architectures so far. You don't say
what architecture your servers machines are.

>
>
> I am looking at this purely from a management/performance view.
>
>
> Any ideas/suggestions?
>
>
> Thanks
>
> Hoss


--
Alex Bennée