Re: [Qemu-devel] Flatview rendering scalability issue

[Sergio Lopez]

Paolo Bonzini writes:

> On 11/03/19 10:26, Sergio Lopez wrote:
>> I guess this is a consequence of having to reset/rebuild the Flatview
>> when altering the PCI BAR regions.
>> 
>> Is this a known issue we're already working on?
>
> What version of QEMU is this?

This upstream as of 6cb4f6db4f4367f (Mar 07 2019).

> The initialization is O(n^2) because the guest initializes one device at
> a time, so you rebuild the FlatView first with 0 devices, then 1, then
> 2, etc.  This is very hard to fix, if at all possible.
>
> However, each FlatView creation should be O(n) where n is the number of
> devices currently configured.  Please check with "info mtree -f" that
> you only have a fixed number of FlatViews.  Old versions had one per device.

I'm seeing 9 FVs with 1 PCI, and 119 with 100 PCIs.

Thanks,
Sergio.