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From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
To: "Michael S. Tsirkin" <mst@redhat.com>,
	Alexander Duyck <alexander.duyck@gmail.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	willy@infradead.org, mhocko@kernel.org, linux-mm@kvack.org,
	akpm@linux-foundation.org, mgorman@techsingularity.net,
	vbabka@suse.cz, yang.zhang.wz@gmail.com, nitesh@redhat.com,
	konrad.wilk@oracle.com, david@redhat.com, pagupta@redhat.com,
	riel@surriel.com, lcapitulino@redhat.com, dave.hansen@intel.com,
	wei.w.wang@intel.com, aarcange@redhat.com, pbonzini@redhat.com,
	dan.j.williams@intel.com, osalvador@suse.de
Subject: Re: [PATCH v15 6/7] virtio-balloon: Add support for providing free page reports to host
Date: Fri, 13 Dec 2019 08:35:13 -0800	[thread overview]
Message-ID: <de779bcc6ccae238dbdedcc61db88abbdb8f291e.camel@linux.intel.com> (raw)
In-Reply-To: <20191213020553-mutt-send-email-mst@kernel.org>

On Fri, 2019-12-13 at 02:08 -0500, Michael S. Tsirkin wrote:
> On Thu, Dec 05, 2019 at 08:22:55AM -0800, Alexander Duyck wrote:
> > From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> > 
> > Add support for the page reporting feature provided by virtio-balloon.
> > Reporting differs from the regular balloon functionality in that is is
> > much less durable than a standard memory balloon. Instead of creating a
> > list of pages that cannot be accessed the pages are only inaccessible
> > while they are being indicated to the virtio interface. Once the
> > interface has acknowledged them they are placed back into their respective
> > free lists and are once again accessible by the guest system.
> > 
> > Unlike a standard balloon we don't inflate and deflate the pages. Instead
> > we perform the reporting, and once the reporting is completed it is
> > assumed that the page has been dropped from the guest and will be faulted
> > back in the next time the page is accessed.
> > 
> > For this reason when I had originally introduced the patch set I referred
> > to this behavior as a "bubble" instead of a "balloon" since the duration
> > is short lived, and when the page is touched the "bubble" is popped and
> > the page is faulted back in.
> > 
> > Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> 
> virtio POV is fine here:
> 
> Acked-by: Michael S. Tsirkin <mst@redhat.com>
> 
> However please copy virtio-comment on UAPI changes.

So I have been avoiding copying virtio-dev on the kernel changes as I had
gotten feedback that it was annoying some people as they were getting
bounces since they were not subscribed. Will the same type of thing happen
with virtio-comment?

> If possible isolate the last chunk in a patch by itself
> to make it easier for non-kernel developers to review.

Are you talking about the change in "include/uapi/linux/virtio_balloon.h"?

I have it as a standalone patch in the QEMU set, and for the QEMU set I
had included virtio-dev. Would you prefer I include virtio-comment instead
or in addition to virtio-dev? My thought is that I would prefer to keep
the virtio people focused on the QEMU code since they are probably more
comfortable with that, and the kernel people focused on the kernel code.

> > ---
> >  drivers/virtio/Kconfig              |    1 +
> >  drivers/virtio/virtio_balloon.c     |   64 +++++++++++++++++++++++++++++++++++
> >  include/uapi/linux/virtio_balloon.h |    1 +
> >  3 files changed, 66 insertions(+)

<snip>

> > 
> > diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
> > index a1966cd7b677..19974392d324 100644
> > --- a/include/uapi/linux/virtio_balloon.h
> > +++ b/include/uapi/linux/virtio_balloon.h
> > @@ -36,6 +36,7 @@
> >  #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM	2 /* Deflate balloon on OOM */
> >  #define VIRTIO_BALLOON_F_FREE_PAGE_HINT	3 /* VQ to report free pages */
> >  #define VIRTIO_BALLOON_F_PAGE_POISON	4 /* Guest is using page poisoning */
> > +#define VIRTIO_BALLOON_F_REPORTING	5 /* Page reporting virtqueue */
> >  
> >  /* Size of a PFN in the balloon interface. */
> >  #define VIRTIO_BALLOON_PFN_SHIFT 12

If this is the bit we are talking about I have it split out already into a
QEMU specific patch as well, it can be found here:
https://lore.kernel.org/lkml/20191205162422.19737.57728.stgit@localhost.localdomain/

If needed I could probably add a cover page and/or update the comments in
that patch if that is needed to better explain the change.

Thanks.

- Alex


  reply	other threads:[~2019-12-13 20:39 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-05 16:22 [PATCH v15 0/7] mm / virtio: Provide support for free page reporting Alexander Duyck
2019-12-05 16:22 ` [PATCH v15 1/7] mm: Adjust shuffle code to allow for future coalescing Alexander Duyck
2019-12-05 16:22 ` [PATCH v15 2/7] mm: Use zone and order instead of free area in free_list manipulators Alexander Duyck
2019-12-05 16:22 ` [PATCH v15 3/7] mm: Add function __putback_isolated_page Alexander Duyck
2019-12-16 11:36   ` David Hildenbrand
2019-12-16 16:22     ` Alexander Duyck
2019-12-17 10:58       ` David Hildenbrand
2019-12-17 16:26         ` Alexander Duyck
2019-12-17 17:24           ` David Hildenbrand
2019-12-17 18:24             ` Alexander Duyck
2019-12-17 18:46               ` David Hildenbrand
2019-12-17 21:50                 ` Alexander Duyck
2019-12-05 16:22 ` [PATCH v15 4/7] mm: Introduce Reported pages Alexander Duyck
2019-12-16 10:17   ` Nitesh Narayan Lal
2019-12-16 16:28     ` Alexander Duyck
2019-12-17  8:55       ` Nitesh Narayan Lal
2019-12-17 16:31         ` Alexander Duyck
2019-12-18  7:31           ` Mel Gorman
2019-12-16 11:44   ` Nitesh Narayan Lal
2019-12-16 16:10     ` Alexander Duyck
2019-12-05 16:22 ` [PATCH v15 5/7] virtio-balloon: Pull page poisoning config out of free page hinting Alexander Duyck
2019-12-13  7:03   ` Michael S. Tsirkin
2019-12-05 16:22 ` [PATCH v15 6/7] virtio-balloon: Add support for providing free page reports to host Alexander Duyck
2019-12-13  7:08   ` Michael S. Tsirkin
2019-12-13 16:35     ` Alexander Duyck [this message]
2019-12-15  9:29       ` Michael S. Tsirkin
2019-12-13 10:15   ` David Hildenbrand
2019-12-13 16:37     ` Alexander Duyck
2019-12-05 16:23 ` [PATCH v15 7/7] mm: Add free page reporting documentation Alexander Duyck
2019-12-05 16:24 ` [PATCH v15 QEMU 1/3] virtio-ballon: Implement support for page poison tracking feature Alexander Duyck
2019-12-05 16:24 ` [PATCH v15 QEMU 2/3] virtio-balloon: Add bit to notify guest of unused page reporting Alexander Duyck
2019-12-05 16:24 ` [PATCH v15 QEMU 3/3] virtio-balloon: Provide a interface for " Alexander Duyck
2019-12-05 16:26 ` [PATCH v15 QEMU 4/3 RFC] memory: Add support for MADV_FREE as mechanism to lazy discard pages Alexander Duyck
2019-12-12 23:47 ` [PATCH v15 0/7] mm / virtio: Provide support for free page reporting Alexander Duyck
2019-12-13 10:00 ` David Hildenbrand
2019-12-13 11:08   ` Mel Gorman
2019-12-13 16:59     ` Alexander Duyck
2019-12-13 16:46   ` Alexander Duyck
2019-12-16 12:21     ` David Hildenbrand

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