Re: [PATCH v8 0/7] mm / virtio: Provide support for unused page reporting

From: Alexander Duyck <alexander.duyck@gmail.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Nitesh Narayan Lal <nitesh@redhat.com>,
	kvm list <kvm@vger.kernel.org>,
	David Hildenbrand <david@redhat.com>,
	Dave Hansen <dave.hansen@intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Matthew Wilcox <willy@infradead.org>,
	Michal Hocko <mhocko@kernel.org>, linux-mm <linux-mm@kvack.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	virtio-dev@lists.oasis-open.org,
	Oscar Salvador <osalvador@suse.de>,
	Yang Zhang <yang.zhang.wz@gmail.com>,
	Pankaj Gupta <pagupta@redhat.com>,
	Rik van Riel <riel@surriel.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	lcapitulino@redhat.com, "Wang, Wei W" <wei.w.wang@intel.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Alexander Duyck <alexander.h.duyck@linux.intel.com>
Subject: Re: [PATCH v8 0/7] mm / virtio: Provide support for unused page reporting
Date: Fri, 6 Sep 2019 20:15:20 -0700	[thread overview]
Message-ID: <CAKgT0UcuZQPzcQ6cA5tKPG3+4yQP2jk+AHYcjoyrMXq0pBAiBw@mail.gmail.com> (raw)
In-Reply-To: <20190906112155-mutt-send-email-mst@kernel.org>

On Fri, Sep 6, 2019 at 8:23 AM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Fri, Sep 06, 2019 at 07:53:21AM -0700, Alexander Duyck wrote:
> > This series provides an asynchronous means of reporting to a hypervisor
> > that a guest page is no longer in use and can have the data associated
> > with it dropped. To do this I have implemented functionality that allows
> > for what I am referring to as unused page reporting
> >
> > The functionality for this is fairly simple. When enabled it will allocate
> > statistics to track the number of reported pages in a given free area.
> > When the number of free pages exceeds this value plus a high water value,
> > currently 32, it will begin performing page reporting which consists of
> > pulling pages off of free list and placing them into a scatter list. The
> > scatterlist is then given to the page reporting device and it will perform
> > the required action to make the pages "reported", in the case of
> > virtio-balloon this results in the pages being madvised as MADV_DONTNEED
> > and as such they are forced out of the guest. After this they are placed
> > back on the free list, and an additional bit is added if they are not
> > merged indicating that they are a reported buddy page instead of a
> > standard buddy page. The cycle then repeats with additional non-reported
> > pages being pulled until the free areas all consist of reported pages.
> >
> > I am leaving a number of things hard-coded such as limiting the lowest
> > order processed to PAGEBLOCK_ORDER, and have left it up to the guest to
> > determine what the limit is on how many pages it wants to allocate to
> > process the hints. The upper limit for this is based on the size of the
> > queue used to store the scattergather list.
>
> I queued this  so this gets tested on linux-next but the mm core changes
> need acks from appropriate people.

Looks like there was a couple issues on arm64 and ia64 architectures.
I believe I have those fixed up and will submit a v9 in the morning
after my test runs have completed.

Thanks.

- Alex