From: "Michael S. Tsirkin" <mst@redhat.com>
To: 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, alexander.h.duyck@linux.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 02:08:19 -0500 [thread overview]
Message-ID: <20191213020553-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20191205162255.19548.63866.stgit@localhost.localdomain>
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.
If possible isolate the last chunk in a patch by itself
to make it easier for non-kernel developers to review.
> ---
> drivers/virtio/Kconfig | 1 +
> drivers/virtio/virtio_balloon.c | 64 +++++++++++++++++++++++++++++++++++
> include/uapi/linux/virtio_balloon.h | 1 +
> 3 files changed, 66 insertions(+)
>
> diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
> index 078615cf2afc..4b2dd8259ff5 100644
> --- a/drivers/virtio/Kconfig
> +++ b/drivers/virtio/Kconfig
> @@ -58,6 +58,7 @@ config VIRTIO_BALLOON
> tristate "Virtio balloon driver"
> depends on VIRTIO
> select MEMORY_BALLOON
> + select PAGE_REPORTING
> ---help---
> This driver supports increasing and decreasing the amount
> of memory within a KVM guest.
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index 252591bc7e01..ecd54edba968 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -19,6 +19,7 @@
> #include <linux/mount.h>
> #include <linux/magic.h>
> #include <linux/pseudo_fs.h>
> +#include <linux/page_reporting.h>
>
> /*
> * Balloon device works in 4K page units. So each page is pointed to by
> @@ -47,6 +48,7 @@ enum virtio_balloon_vq {
> VIRTIO_BALLOON_VQ_DEFLATE,
> VIRTIO_BALLOON_VQ_STATS,
> VIRTIO_BALLOON_VQ_FREE_PAGE,
> + VIRTIO_BALLOON_VQ_REPORTING,
> VIRTIO_BALLOON_VQ_MAX
> };
>
> @@ -114,6 +116,10 @@ struct virtio_balloon {
>
> /* To register a shrinker to shrink memory upon memory pressure */
> struct shrinker shrinker;
> +
> + /* Free page reporting device */
> + struct virtqueue *reporting_vq;
> + struct page_reporting_dev_info pr_dev_info;
> };
>
> static struct virtio_device_id id_table[] = {
> @@ -153,6 +159,33 @@ static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
>
> }
>
> +int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_info,
> + struct scatterlist *sg, unsigned int nents)
> +{
> + struct virtio_balloon *vb =
> + container_of(pr_dev_info, struct virtio_balloon, pr_dev_info);
> + struct virtqueue *vq = vb->reporting_vq;
> + unsigned int unused, err;
> +
> + /* We should always be able to add these buffers to an empty queue. */
> + err = virtqueue_add_inbuf(vq, sg, nents, vb, GFP_NOWAIT | __GFP_NOWARN);
> +
> + /*
> + * In the extremely unlikely case that something has occurred and we
> + * are able to trigger an error we will simply display a warning
> + * and exit without actually processing the pages.
> + */
> + if (WARN_ON_ONCE(err))
> + return err;
> +
> + virtqueue_kick(vq);
> +
> + /* When host has read buffer, this completes via balloon_ack */
> + wait_event(vb->acked, virtqueue_get_buf(vq, &unused));
> +
> + return 0;
> +}
> +
> static void set_page_pfns(struct virtio_balloon *vb,
> __virtio32 pfns[], struct page *page)
> {
> @@ -477,6 +510,7 @@ static int init_vqs(struct virtio_balloon *vb)
> names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
> names[VIRTIO_BALLOON_VQ_STATS] = NULL;
> names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
> + names[VIRTIO_BALLOON_VQ_REPORTING] = NULL;
>
> if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
> names[VIRTIO_BALLOON_VQ_STATS] = "stats";
> @@ -488,6 +522,11 @@ static int init_vqs(struct virtio_balloon *vb)
> callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
> }
>
> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
> + names[VIRTIO_BALLOON_VQ_REPORTING] = "reporting_vq";
> + callbacks[VIRTIO_BALLOON_VQ_REPORTING] = balloon_ack;
> + }
> +
> err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX,
> vqs, callbacks, names, NULL, NULL);
> if (err)
> @@ -520,6 +559,9 @@ static int init_vqs(struct virtio_balloon *vb)
> if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
> vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE];
>
> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
> + vb->reporting_vq = vqs[VIRTIO_BALLOON_VQ_REPORTING];
> +
> return 0;
> }
>
> @@ -939,12 +981,31 @@ static int virtballoon_probe(struct virtio_device *vdev)
> if (err)
> goto out_del_balloon_wq;
> }
> +
> + vb->pr_dev_info.report = virtballoon_free_page_report;
> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
> + unsigned int capacity;
> +
> + capacity = virtqueue_get_vring_size(vb->reporting_vq);
> + if (capacity < PAGE_REPORTING_CAPACITY) {
> + err = -ENOSPC;
> + goto out_unregister_shrinker;
> + }
> +
> + err = page_reporting_register(&vb->pr_dev_info);
> + if (err)
> + goto out_unregister_shrinker;
> + }
> +
> virtio_device_ready(vdev);
>
> if (towards_target(vb))
> virtballoon_changed(vdev);
> return 0;
>
> +out_unregister_shrinker:
> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
> + virtio_balloon_unregister_shrinker(vb);
> out_del_balloon_wq:
> if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
> destroy_workqueue(vb->balloon_wq);
> @@ -973,6 +1034,8 @@ static void virtballoon_remove(struct virtio_device *vdev)
> {
> struct virtio_balloon *vb = vdev->priv;
>
> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
> + page_reporting_unregister(&vb->pr_dev_info);
> if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
> virtio_balloon_unregister_shrinker(vb);
> spin_lock_irq(&vb->stop_update_lock);
> @@ -1045,6 +1108,7 @@ static int virtballoon_validate(struct virtio_device *vdev)
> VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
> VIRTIO_BALLOON_F_FREE_PAGE_HINT,
> VIRTIO_BALLOON_F_PAGE_POISON,
> + VIRTIO_BALLOON_F_REPORTING,
> };
>
> static struct virtio_driver virtio_balloon_driver = {
> 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
next prev parent reply other threads:[~2019-12-13 7:08 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 [this message]
2019-12-13 16:35 ` Alexander Duyck
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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