[Qemu-devel] RFC migration of zero pages

[Peter Lieven]

Hi,

I just came across an idea and would like to have feedback if it makes sence or 
not.

If a VM is started without preallocated memory all memory that has not been 
written to
reads as zeros, right?
If a VM with a lot of unwritten memory is migrated or if the memory contains a 
lot
of zeroed out memory (e.g. Windows or Linux guest with page sanitization) all 
this memory
is allocated on the target during live migration. Especially with KSM this leads
to the problem that this memory is allocated and might be not available 
completely as
merging of the pages will happen async.

Wouldn't it make sense to not send zero pages in the first round where the 
complete
ram is sent (if it is detectable that we are in this stage)?

Peter