Re: [RFC PATCH 0/4] KVM: ioctl for populating guest_memfd

David Hildenbrand
2024-11-20T16:44:09Z

>> No, I can't immediately see why it shouldn't work. My main concern
>> would probably still be about the latency of the population stage as I
>> can't see why it would improve compared to what we have now, because my
> > feeling is this is linked with the sharedness property of guest_memfd.
>
> If the problem is the "pagecache" overhead, then yes, it will be a
> harder nut to crack. But maybe there are some low-hanging fruits to
> optimize? Finding the main cause for the added overhead would be
> interesting.

Can you compare uffdio_copy() when using anonymous memory vs. shmem?
That's likely the best we could currently achieve with guest_memfd.

There is the tools/testing/selftests/mm/uffd-stress benchmark, not sure
if that is of any help; it SEGFAULTS for me right now with a (likely)
division by 0.

--
Cheers,

David / dhildenb