On Fri, Oct 20, 2017 at 07:54:25PM +0800, Wei Wang wrote:
> The current implementation only deflates 256 pages even when a user
> specifies more than that via the oom_pages module param. This patch
> enables the deflating of up to oom_pages pages if there are enough
> inflated pages.
>
> Signed-off-by: Wei Wang <wei.w.wang@xxxxxxxxx>
> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxxxx>
> Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
This seems reasonable. Does this by itself help?
> ---
> drivers/virtio/virtio_balloon.c | 14 +++++++++-----
> 1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index 1ecd15a..ab55cf8 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -43,8 +43,8 @@
> #define OOM_VBALLOON_DEFAULT_PAGES 256
> #define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
>
> -static int oom_pages = OOM_VBALLOON_DEFAULT_PAGES;
> -module_param(oom_pages, int, S_IRUSR | S_IWUSR);
> +static unsigned int oom_pages = OOM_VBALLOON_DEFAULT_PAGES;
> +module_param(oom_pages, uint, 0600);
> MODULE_PARM_DESC(oom_pages, "pages to free on OOM");
>
> #ifdef CONFIG_BALLOON_COMPACTION
> @@ -359,16 +359,20 @@ static int virtballoon_oom_notify(struct notifier_block *self,
> {
> struct virtio_balloon *vb;
> unsigned long *freed;
> - unsigned num_freed_pages;
> + unsigned int npages = oom_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);
> +
> + /* Don't deflate more than the number of inflated pages */
> + while (npages && atomic64_read(&vb->num_pages))
> + npages -= leak_balloon(vb, npages);
> +
> update_balloon_size(vb);
> - *freed += num_freed_pages;
> + *freed += oom_pages - npages;
>
> return NOTIFY_OK;
> }
> --
> 2.7.4
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