Re: [Qemu-devel] Question about qemu firmware configuration (fw_cfg) device

[Alexander Graf]

On 19.07.2010, at 09:33, Gleb Natapov wrote:

> On Mon, Jul 19, 2010 at 08:28:02AM +0100, Richard W.M. Jones wrote:
>> On Mon, Jul 19, 2010 at 09:23:56AM +0300, Gleb Natapov wrote:
>>> That what I am warring about too. If we are adding device we have to be
>>> sure such device can actually exist on real hw too otherwise we may have
>>> problems later.
>> 
>> I don't understand why the constraints of real h/w have anything to do
>> with this.  Can you explain?
>> 
> Each time we do something not architectural it cause us troubles later.
> So constraints of real h/w is our constrains to.
> 
>>> Also 1 second on 100M file does not look like huge gain to me.
>> 
>> Every second counts.  We're trying to get libguestfs boot times down
>> from 8-12 seconds to 4-5 seconds.  For many cases it's an interactive
>> program.
>> 
> So what about making initrd smaller? I remember managing two
> distribution in 64M flash in embedded project.

Having a huge initrd basically helps in reusing a lot of existing code. We do 
the same - in general the initrd is just a subset of the applications of the 
host OS. And if you start putting perl or the likes into it, it becomes big.

I guess the best thing for now really is to try and see which code paths insb 
goes along. It should really be coalesced.

Richard, what does kvm_stat tell you while loading the initrd? Are there a lot 
of PIO requests or are we simply looping inside qemu code?


Alex