Re: [Qemu-devel] [PATCH qemu v4 18/18] memory: Give memory_region_transaction_commit a hint

[Paolo Bonzini]

On 20/09/2017 13:46, Alexey Kardashevskiy wrote:
> This extends memory_region_transaction_commit() to receive a MR as
> if it is a root MR or its topmost parent is, then we can only rebuild
> its FlatView and update it for address spaces sharing it.
> 
> The optimization gets disabled though if there is full update about to
> commit.
> 
> memory_region_set_enabled() is a special case here, it does not use
> a hint when MR is being disabled.
> 
> On POWER8 with 255 CPUs, 255 virtio-net, 40 PCI bridges guest this brings
> down the boot time from 20s to 12s, the total memory footprint
> goes down (17G -> 8G).

I think this is incorrect if MR has an alias (no matter if enabling or
disabling)?

Paolo