Re: [PATCH v25 1/2 RESEND] mm: support reporting free page blocks

[Andrew Morton]

On Thu, 25 Jan 2018 17:38:27 +0800 Wei Wang <wei.w.wang@xxxxxxxxx> wrote:

> This patch adds support to walk through the free page blocks in the
> system and report them via a callback function. Some page blocks may
> leave the free list after zone->lock is released, so it is the caller's
> responsibility to either detect or prevent the use of such pages.
> 
> One use example of this patch is to accelerate live migration by skipping
> the transfer of free pages reported from the guest. A popular method used
> by the hypervisor to track which part of memory is written during live
> migration is to write-protect all the guest memory. So, those pages that
> are reported as free pages but are written after the report function
> returns will be captured by the hypervisor, and they will be added to the
> next round of memory transfer.

It would be useful if we had some quantitative testing results, so we
can see the real-world benefits from this change?