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Wei Wang

2018-Jul-27 09:24 UTC

[PATCH v2 0/2] virtio-balloon: some improvements

This series is split from the "Virtio-balloon: support free page
reporting" series to make some improvements.

v1->v2 ChangeLog:
- register the shrinker when VIRTIO_BALLOON_F_DEFLATE_ON_OOM is negotiated.

Wei Wang (2):
  virtio-balloon: remove BUG() in init_vqs
  virtio_balloon: replace oom notifier with shrinker

 drivers/virtio/virtio_balloon.c | 125 +++++++++++++++++++++++-----------------
 1 file changed, 72 insertions(+), 53 deletions(-)

-- 
2.7.4

Wei Wang

2018-Jul-27 09:24 UTC

head link

[PATCH v2 1/2] virtio-balloon: remove BUG() in init_vqs

It's a bit overkill to use BUG when failing to add an entry to the
stats_vq in init_vqs. So remove it and just return the error to the
caller to bail out nicely.

Signed-off-by: Wei Wang <wei.w.wang at intel.com>
Cc: Michael S. Tsirkin <mst at redhat.com>
---
 drivers/virtio/virtio_balloon.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 6b237e3..9356a1a 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -455,9 +455,13 @@ static int init_vqs(struct virtio_balloon *vb)
 		num_stats = update_balloon_stats(vb);
 
 		sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
-		if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)
-		    < 0)
-			BUG();
+		err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb,
+					   GFP_KERNEL);
+		if (err) {
+			dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
+				 __func__);
+			return err;
+		}
 		virtqueue_kick(vb->stats_vq);
 	}
 	return 0;
-- 
2.7.4

Wei Wang

2018-Jul-27 09:24 UTC

head link

[PATCH v2 2/2] virtio_balloon: replace oom notifier with shrinker

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 at intel.com>
Cc: Michael S. Tsirkin <mst at redhat.com>
Cc: Michal Hocko <mhocko at kernel.org>
Cc: Andrew Morton <akpm at linux-foundation.org>
---
 drivers/virtio/virtio_balloon.c | 115 +++++++++++++++++++++++-----------------
 1 file changed, 65 insertions(+), 50 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 9356a1a..6b2229b 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 +515,54 @@ 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);
+
+	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 +595,10 @@ 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;
 	}
 
@@ -599,13 +607,20 @@ 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
-
+	/*
+	 * We continue to use VIRTIO_BALLOON_F_DEFLATE_ON_OOM to decide if a
+	 * shrinker needs to be registered to relieve memory pressure.
+	 */
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
+		err = virtio_balloon_register_shrinker(vb);
+		if (err)
+			goto out_del_vqs;
+	}
 	virtio_device_ready(vdev);
 
 	if (towards_target(vb))
@@ -637,8 +652,8 @@ static void virtballoon_remove(struct virtio_device *vdev)
 {
 	struct virtio_balloon *vb = vdev->priv;
 
-	unregister_oom_notifier(&vb->nb);
-
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
+		virtio_balloon_unregister_shrinker(vb);
 	spin_lock_irq(&vb->stop_update_lock);
 	vb->stop_update = true;
 	spin_unlock_irq(&vb->stop_update_lock);
-- 
2.7.4

Michael S. Tsirkin

2018-Jul-27 14:06 UTC

head link

[PATCH v2 0/2] virtio-balloon: some improvements

On Fri, Jul 27, 2018 at 05:24:53PM +0800, Wei Wang
wrote:> This series is split from the "Virtio-balloon: support free page
> reporting" series to make some improvements.
> 
> v1->v2 ChangeLog:
> - register the shrinker when VIRTIO_BALLOON_F_DEFLATE_ON_OOM is negotiated.
> 
> Wei Wang (2):
>   virtio-balloon: remove BUG() in init_vqs
>   virtio_balloon: replace oom notifier with shrinker
Thanks!
Given it's very late in the release cycle, I'll merge this for
the next Linux release.
>  drivers/virtio/virtio_balloon.c | 125
+++++++++++++++++++++++-----------------
>  1 file changed, 72 insertions(+), 53 deletions(-)
> 
> -- 
> 2.7.4

Wang, Wei W

2018-Jul-28 02:00 UTC

head link

[PATCH v2 0/2] virtio-balloon: some improvements

On Friday, July 27, 2018 10:06 PM, Michael S. Tsirkin
wrote:> On Fri, Jul 27, 2018 at 05:24:53PM +0800, Wei Wang wrote:
> > This series is split from the "Virtio-balloon: support free page
> > reporting" series to make some improvements.
> >
> > v1->v2 ChangeLog:
> > - register the shrinker when VIRTIO_BALLOON_F_DEFLATE_ON_OOM is
> negotiated.
> >
> > Wei Wang (2):
> >   virtio-balloon: remove BUG() in init_vqs
> >   virtio_balloon: replace oom notifier with shrinker
> 
> Thanks!
> Given it's very late in the release cycle, I'll merge this for the
next Linux
> release.
No problem. Thanks!

Best,
Wei

Michal Hocko

2018-Jul-30 09:00 UTC

head link

[PATCH v2 2/2] virtio_balloon: replace oom notifier with shrinker

On Fri 27-07-18 17:24:55, Wei Wang wrote:> 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.
It would be great to document the replacement. This is not a small
change...
> 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 at intel.com>
> Cc: Michael S. Tsirkin <mst at redhat.com>
> Cc: Michal Hocko <mhocko at kernel.org>
> Cc: Andrew Morton <akpm at linux-foundation.org>
> ---
>  drivers/virtio/virtio_balloon.c | 115
+++++++++++++++++++++++-----------------
>  1 file changed, 65 insertions(+), 50 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_balloon.c
b/drivers/virtio/virtio_balloon.c
> index 9356a1a..6b2229b 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 +515,54 @@ 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);
> +
> +	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 +595,10 @@ 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;
>  	}
>  
> @@ -599,13 +607,20 @@ 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
> -
> +	/*
> +	 * We continue to use VIRTIO_BALLOON_F_DEFLATE_ON_OOM to decide if a
> +	 * shrinker needs to be registered to relieve memory pressure.
> +	 */
> +	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
> +		err = virtio_balloon_register_shrinker(vb);
> +		if (err)
> +			goto out_del_vqs;
> +	}
>  	virtio_device_ready(vdev);
>  
>  	if (towards_target(vb))
> @@ -637,8 +652,8 @@ static void virtballoon_remove(struct virtio_device
*vdev)
>  {
>  	struct virtio_balloon *vb = vdev->priv;
>  
> -	unregister_oom_notifier(&vb->nb);
> -
> +	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
> +		virtio_balloon_unregister_shrinker(vb);
>  	spin_lock_irq(&vb->stop_update_lock);
>  	vb->stop_update = true;
>  	spin_unlock_irq(&vb->stop_update_lock);
> -- 
> 2.7.4
-- 
Michal Hocko
SUSE Labs

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