From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Wang Subject: [PATCH RFC] virtio_balloon: conservative balloon page shrinking Date: Thu, 6 Feb 2020 16:01:47 +0800 Message-ID: <1580976107-16013-1-git-send-email-wei.w.wang@intel.com> Return-path: Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org Cc: tysand@google.com, mst@redhat.com, david@redhat.com, alexander.h.duyck@linux.intel.com, rientjes@google.com, mhocko@kernel.org, namit@vmware.com, penguin-kernel@I-love.SAKURA.ne.jp, wei.w.wang@intel.com List-Id: virtualization@lists.linuxfoundation.org There are cases that users want to shrink balloon pages after the pagecache depleted. The conservative_shrinker lets the shrinker shrink balloon pages when all the pagecache has been reclaimed. Signed-off-by: Wei Wang --- drivers/virtio/virtio_balloon.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 93f995f6cf36..b4c5bb13a867 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -42,6 +42,10 @@ static struct vfsmount *balloon_mnt; #endif +static bool conservative_shrinker = true; +module_param(conservative_shrinker, bool, 0644); +MODULE_PARM_DESC(conservative_shrinker, "conservatively shrink balloon pages"); + enum virtio_balloon_vq { VIRTIO_BALLOON_VQ_INFLATE, VIRTIO_BALLOON_VQ_DEFLATE, @@ -796,6 +800,10 @@ static unsigned long shrink_balloon_pages(struct virtio_balloon *vb, { unsigned long pages_freed = 0; + /* Balloon pages only gets shrunk when the pagecache depleted */ + if (conservative_shrinker && global_node_page_state(NR_FILE_PAGES)) + return 0; + /* * One invocation of leak_balloon can deflate at most * VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it @@ -837,7 +845,11 @@ static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker, struct virtio_balloon, shrinker); unsigned long count; - count = vb->num_pages / VIRTIO_BALLOON_PAGES_PER_PAGE; + if (conservative_shrinker && global_node_page_state(NR_FILE_PAGES)) + count = 0; + else + count = vb->num_pages / VIRTIO_BALLOON_PAGES_PER_PAGE; + count += vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES; return count; -- 2.17.1