From: Wei Wang <wei.w.wang@intel.com>
To: virtio-dev@lists.oasis-open.org, linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
linux-mm@kvack.org, mst@redhat.com, mhocko@kernel.org,
akpm@linux-foundation.org, torvalds@linux-foundation.org
Cc: pbonzini@redhat.com, wei.w.wang@intel.com,
liliang.opensource@gmail.com, yang.zhang.wz@gmail.com,
quan.xu0@gmail.com, nilal@redhat.com, riel@redhat.com,
peterx@redhat.com
Subject: [PATCH v36 2/5] virtio_balloon: replace oom notifier with shrinker
Date: Fri, 20 Jul 2018 16:33:02 +0800 [thread overview]
Message-ID: <1532075585-39067-3-git-send-email-wei.w.wang@intel.com> (raw)
In-Reply-To: <1532075585-39067-1-git-send-email-wei.w.wang@intel.com>
The OOM notifier is getting deprecated to use for the reasons mentioned
here by Michal Hocko: https://lkml.org/lkml/2018/7/12/314
This patch replaces the virtio-balloon oom notifier with a shrinker
to release balloon pages on memory pressure.
In addition, the bug in the replaced virtballoon_oom_notify that only
VIRTIO_BALLOON_ARRAY_PFNS_MAX (i.e 256) balloon pages can be freed
though the user has specified more than that number is fixed in the
shrinker_scan function.
Signed-off-by: Wei Wang <wei.w.wang@intel.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
---
drivers/virtio/virtio_balloon.c | 113 +++++++++++++++++++++++-----------------
1 file changed, 65 insertions(+), 48 deletions(-)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 9356a1a..c6fd406 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -27,7 +27,6 @@
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/balloon_compaction.h>
-#include <linux/oom.h>
#include <linux/wait.h>
#include <linux/mm.h>
#include <linux/mount.h>
@@ -40,12 +39,12 @@
*/
#define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
#define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
-#define OOM_VBALLOON_DEFAULT_PAGES 256
+#define DEFAULT_BALLOON_PAGES_TO_SHRINK 256
#define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
-static int oom_pages = OOM_VBALLOON_DEFAULT_PAGES;
-module_param(oom_pages, int, S_IRUSR | S_IWUSR);
-MODULE_PARM_DESC(oom_pages, "pages to free on OOM");
+static unsigned long balloon_pages_to_shrink = DEFAULT_BALLOON_PAGES_TO_SHRINK;
+module_param(balloon_pages_to_shrink, ulong, 0600);
+MODULE_PARM_DESC(balloon_pages_to_shrink, "pages to free on memory presure");
#ifdef CONFIG_BALLOON_COMPACTION
static struct vfsmount *balloon_mnt;
@@ -86,8 +85,8 @@ struct virtio_balloon {
/* Memory statistics */
struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
- /* To register callback in oom notifier call chain */
- struct notifier_block nb;
+ /* To register a shrinker to shrink memory upon memory pressure */
+ struct shrinker shrinker;
};
static struct virtio_device_id id_table[] = {
@@ -365,38 +364,6 @@ static void update_balloon_size(struct virtio_balloon *vb)
&actual);
}
-/*
- * virtballoon_oom_notify - release pages when system is under severe
- * memory pressure (called from out_of_memory())
- * @self : notifier block struct
- * @dummy: not used
- * @parm : returned - number of freed pages
- *
- * The balancing of memory by use of the virtio balloon should not cause
- * the termination of processes while there are pages in the balloon.
- * If virtio balloon manages to release some memory, it will make the
- * system return and retry the allocation that forced the OOM killer
- * to run.
- */
-static int virtballoon_oom_notify(struct notifier_block *self,
- unsigned long dummy, void *parm)
-{
- struct virtio_balloon *vb;
- unsigned long *freed;
- unsigned num_freed_pages;
-
- vb = container_of(self, struct virtio_balloon, nb);
- if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
- return NOTIFY_OK;
-
- freed = parm;
- num_freed_pages = leak_balloon(vb, oom_pages);
- update_balloon_size(vb);
- *freed += num_freed_pages;
-
- return NOTIFY_OK;
-}
-
static void update_balloon_stats_func(struct work_struct *work)
{
struct virtio_balloon *vb;
@@ -548,6 +515,61 @@ static struct file_system_type balloon_fs = {
#endif /* CONFIG_BALLOON_COMPACTION */
+static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
+ struct shrink_control *sc)
+{
+ unsigned long pages_to_free = balloon_pages_to_shrink,
+ pages_freed = 0;
+ struct virtio_balloon *vb = container_of(shrinker,
+ struct virtio_balloon, shrinker);
+
+ /*
+ * One invocation of leak_balloon can deflate at most
+ * VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it
+ * multiple times to deflate pages till reaching
+ * balloon_pages_to_shrink pages.
+ */
+ while (vb->num_pages && pages_to_free) {
+ pages_to_free = balloon_pages_to_shrink - pages_freed;
+ pages_freed += leak_balloon(vb, pages_to_free);
+ }
+ update_balloon_size(vb);
+
+ return pages_freed / VIRTIO_BALLOON_PAGES_PER_PAGE;
+}
+
+static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
+ struct shrink_control *sc)
+{
+ struct virtio_balloon *vb = container_of(shrinker,
+ struct virtio_balloon, shrinker);
+
+ /*
+ * We continue to use VIRTIO_BALLOON_F_DEFLATE_ON_OOM to handle the
+ * case when shrinker needs to be invoked to relieve memory pressure.
+ */
+ if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
+ return 0;
+
+ return min_t(unsigned long, vb->num_pages, balloon_pages_to_shrink) /
+ VIRTIO_BALLOON_PAGES_PER_PAGE;
+}
+
+static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
+{
+ unregister_shrinker(&vb->shrinker);
+}
+
+static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
+{
+ vb->shrinker.scan_objects = virtio_balloon_shrinker_scan;
+ vb->shrinker.count_objects = virtio_balloon_shrinker_count;
+ vb->shrinker.batch = 0;
+ vb->shrinker.seeks = DEFAULT_SEEKS;
+
+ return register_shrinker(&vb->shrinker);
+}
+
static int virtballoon_probe(struct virtio_device *vdev)
{
struct virtio_balloon *vb;
@@ -580,17 +602,10 @@ static int virtballoon_probe(struct virtio_device *vdev)
if (err)
goto out_free_vb;
- vb->nb.notifier_call = virtballoon_oom_notify;
- vb->nb.priority = VIRTBALLOON_OOM_NOTIFY_PRIORITY;
- err = register_oom_notifier(&vb->nb);
- if (err < 0)
- goto out_del_vqs;
-
#ifdef CONFIG_BALLOON_COMPACTION
balloon_mnt = kern_mount(&balloon_fs);
if (IS_ERR(balloon_mnt)) {
err = PTR_ERR(balloon_mnt);
- unregister_oom_notifier(&vb->nb);
goto out_del_vqs;
}
@@ -599,12 +614,14 @@ static int virtballoon_probe(struct virtio_device *vdev)
if (IS_ERR(vb->vb_dev_info.inode)) {
err = PTR_ERR(vb->vb_dev_info.inode);
kern_unmount(balloon_mnt);
- unregister_oom_notifier(&vb->nb);
vb->vb_dev_info.inode = NULL;
goto out_del_vqs;
}
vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops;
#endif
+ err = virtio_balloon_register_shrinker(vb);
+ if (err)
+ goto out_del_vqs;
virtio_device_ready(vdev);
@@ -637,7 +654,7 @@ static void virtballoon_remove(struct virtio_device *vdev)
{
struct virtio_balloon *vb = vdev->priv;
- unregister_oom_notifier(&vb->nb);
+ virtio_balloon_unregister_shrinker(vb);
spin_lock_irq(&vb->stop_update_lock);
vb->stop_update = true;
--
2.7.4
next prev parent reply other threads:[~2018-07-20 9:00 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-20 8:33 [PATCH v36 0/5] Virtio-balloon: support free page reporting Wei Wang
2018-07-20 8:33 ` [PATCH v36 1/5] virtio-balloon: remove BUG() in init_vqs Wei Wang
2018-07-20 8:33 ` Wei Wang [this message]
2018-07-22 14:48 ` [PATCH v36 2/5] virtio_balloon: replace oom notifier with shrinker Michael S. Tsirkin
2018-07-23 10:30 ` Wei Wang
2018-07-23 14:13 ` Michael S. Tsirkin
2018-07-24 1:49 ` Wei Wang
2018-07-20 8:33 ` [PATCH v36 3/5] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT Wei Wang
2018-07-20 8:33 ` [PATCH v36 4/5] mm/page_poison: expose page_poisoning_enabled to kernel modules Wei Wang
2018-07-20 8:33 ` [PATCH v36 5/5] virtio-balloon: VIRTIO_BALLOON_F_PAGE_POISON Wei Wang
2018-07-20 12:51 ` [PATCH v36 0/5] Virtio-balloon: support free page reporting Michael S. Tsirkin
2018-07-22 11:11 ` Wang, Wei W
2018-07-23 14:07 ` Michael S. Tsirkin
2018-07-23 14:36 ` Dr. David Alan Gilbert
2018-07-24 8:12 ` Wei Wang
2018-09-06 12:18 ` Wei Wang
2018-09-07 12:29 ` Dr. David Alan Gilbert
2018-09-08 1:46 ` Wang, Wei W
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