Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Mon, 18 Nov 2019 18:08:56 -0500
From:   "Michael S. Tsirkin" <mst@redhat.com>
To:     Khazhismel Kumykov <khazhy@google.com>
Cc:     jasowang@redhat.com, wei.w.wang@intel.com,
        linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org
Subject: Re: [PATCH 1/2] virtio_balloon: fix pages_to_free calculation
Message-ID: <20191118175648-mutt-send-email-mst@kernel.org>
References: <CACGdZYJoHSN3vkj_QBz6Txmec9mJMmkH66j2XtqzpUWpfpw4Tg@mail.gmail.com>
 <20191118213811.22017-1-khazhy@google.com>
MIME-Version: 1.0
In-Reply-To: <20191118213811.22017-1-khazhy@google.com>
Content-Type: text/plain; charset=WINDOWS-1252
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


So I really think we should do something like the below instead.
Limit playing with balloon pages so we can gradually limit it to legacy.
Testing, review would be appreciated.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>


diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloo=
n.c
index 226fbb995fb0..7cee05cdf3fb 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -772,6 +772,13 @@ static unsigned long shrink_free_pages(struct virtio_b=
alloon *vb,
 =09return blocks_freed << VIRTIO_BALLOON_FREE_PAGE_ORDER;
 }
=20
+static unsigned long leak_balloon_pages(struct virtio_balloon *vb,
+                                          unsigned long pages_to_free)
+{
+=09return leak_balloon(vb, pages_to_free * VIRTIO_BALLOON_PAGES_PER_PAGE) =
/
+=09=09VIRTIO_BALLOON_PAGES_PER_PAGE;
+}
+
 static unsigned long shrink_balloon_pages(struct virtio_balloon *vb,
 =09=09=09=09=09  unsigned long pages_to_free)
 {
@@ -782,11 +789,9 @@ static unsigned long shrink_balloon_pages(struct virti=
o_balloon *vb,
 =09 * VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it
 =09 * multiple times to deflate pages till reaching pages_to_free.
 =09 */
-=09while (vb->num_pages && pages_to_free) {
-=09=09pages_freed +=3D leak_balloon(vb, pages_to_free) /
-=09=09=09=09=09VIRTIO_BALLOON_PAGES_PER_PAGE;
-=09=09pages_to_free -=3D pages_freed;
-=09}
+=09while (vb->num_pages && pages_freed < pages_to_free)
+=09=09pages_freed +=3D leak_balloon_pages(vb, pages_to_free);
+
 =09update_balloon_size(vb);
=20
 =09return pages_freed;
@@ -799,7 +804,7 @@ static unsigned long virtio_balloon_shrinker_scan(struc=
t shrinker *shrinker,
 =09struct virtio_balloon *vb =3D container_of(shrinker,
 =09=09=09=09=09struct virtio_balloon, shrinker);
=20
-=09pages_to_free =3D sc->nr_to_scan * VIRTIO_BALLOON_PAGES_PER_PAGE;
+=09pages_to_free =3D sc->nr_to_scan;
=20
 =09if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 =09=09pages_freed =3D shrink_free_pages(vb, pages_to_free);