RE: [RESEND PATCH v3 kernel 0/7] Extend virtio-balloon for fast (de)inflating & fast live migration

On 10/26/2016 03:06 AM, Li, Liang Z wrote:

quoted

I am working on Dave's new bitmap schema, I have finished the part of
getting the 'hybrid scheme bitmap' and found the complexity was more
than I expected. The main issue is more memory is required to save the
'hybrid scheme bitmap' beside that used to save the raw page bitmap,
for the worst case, the memory required is 3 times than that in the
previous implementation.

Really?  Could you please describe the scenario where this occurs?

quoted

I am wondering if I should continue, as an alternative solution, how
about using PFNs array when inflating/deflating only a few pages?
Things will be much more simple.

Yes, using pfn lists is more efficient than using bitmaps for sparse bitmaps.
Yes, there will be cases where it is preferable to just use pfn lists vs. any kind
of bitmap.

But, what does it matter?  At least with your current scheme where we go
out and collect get_unused_pages(), we do the allocation up front.  The
space efficiency doesn't matter at all for small sizes since we do the constant-
size allocation *anyway*.

I'm also pretty sure you can pack the pfn and page order into a single 64-bit
word and have no bitmap for a given record.  That would make it pack just as
well as the old pfns alone.  Right?

Yes, thanks for reminding, I am using 128 bit now, I will change it to 64 bit.
Let me finish the v4 first.

Thanks!
Liang