Re: [PATCH v11 4/6] mm: function to offer a page block on the free list

From: Rik van Riel
Date: Tue Jun 20 2017 - 12:44:30 EST

On Mon, 2017-06-12 at 07:10 -0700, Dave Hansen wrote:

> The hypervisor is going to throw away the contents of these pages,
> right?ÂÂAs soon as the spinlock is released, someone can allocate a
> page, and put good data in it.ÂÂWhat keeps the hypervisor from
> throwing
> away good data?

That looks like it may be the wrong API, then?

We already have hooks called arch_free_page and
arch_alloc_page in the VM, which are called when
pages are freed, and allocated, respectively.

Nitesh Lal (on the CC list) is working on a way
to efficiently batch recently freed pages for
free page hinting to the hypervisor.

If that is done efficiently enough (eg. with
MADV_FREE on the hypervisor side for lazy freeing,
and lazy later re-use of the pages), do we still
need the harder to use batch interface from this

All rights reversed

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