Re: [PATCH 2/2] KVM: Scalable memslots implementation

[Paolo Bonzini <pbonzini@redhat.com>]

On 03/02/21 00:43, Sean Christopherson wrote:
>> But overall, this solution (and the one with id_to_index moved into the
>> main array, too) is still O(n) per memslot operation as you still need to
>> copy the array to either make space for the new memslot or to remove the
>> hole from the removed memslot.
> 
> Yes, but that problem that can be solved separately from the performance issue
> with hva lookups.

I know the world is not just QEMU, but I'll note that in QEMU all 
memslot operations are roughly O(n) anyway.

> Dumping everything into a single patch makes bisecting nearly worthless, e.g. if
> fast hva lookups breaks a non-x86 architecture, we should able to bisect to
> exactly that, not a massive patch that completely rewrites all of the memslot
> code in one fell swoop.
> 
> Mega patches with multiple logical changes are also extremely difficult to
> review.

Indeed.  This patch does get a +1 for having associated selftests, but 
the diffstat puts it back at the bottom of the pile. :)

Paolo