Michael S. Tsirkin
2022-Jun-27 20:42 UTC
[PATCH 1/1] Create debugfs file with virtio balloon usage information
On Mon, Jun 27, 2022 at 07:19:09PM +0000, Alexander Atanasov wrote:> Allow the guest to know how much it is ballooned by the host. > It is useful when debugging out of memory conditions. > > When host gets back memory from the guest it is accounted > as used memory in the guest but the guest have no way to know > how much it is actually ballooned. > > No pretty printing and fixed as per coding style. > > Signed-off-by: Alexander Atanasov <alexander.atanasov at virtuozzo.com> > --- > drivers/virtio/virtio_balloon.c | 71 +++++++++++++++++++++++++++++++++ > 1 file changed, 71 insertions(+) > > - Leave pretty print to userspace > - Fixed coding style > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > index b9737da6c4dd..1bb6a6d0e37b 100644 > --- a/drivers/virtio/virtio_balloon.c > +++ b/drivers/virtio/virtio_balloon.c > @@ -10,6 +10,7 @@ > #include <linux/virtio_balloon.h> > #include <linux/swap.h> > #include <linux/workqueue.h> > +#include <linux/debugfs.h> > #include <linux/delay.h> > #include <linux/slab.h> > #include <linux/module.h> > @@ -731,6 +732,71 @@ static void report_free_page_func(struct work_struct *work) > } > } > > +/* > + * DEBUGFS Interface > + */ > +#ifdef CONFIG_DEBUG_FS > + > +/** > + * virtio_balloon_debug_show - shows statistics of balloon operations. > + * @f: pointer to the &struct seq_file. > + * @offset: ignored. > + * > + * Provides the statistics that can be accessed in virtio-balloon in the debugfs. > + * > + * Return: zero on success or an error code. > + */ > +static int virtio_balloon_debug_show(struct seq_file *f, void *offset) > +{ > + struct virtio_balloon *b = f->private; > + u32 num_pages; > + struct sysinfo i; > + > + si_meminfo(&i); > + > + seq_printf(f, "%-22s: %llx\n", "capabilities", b->vdev->features);why do we need this in debugfs? Isn't this available in sysfs already?> + seq_printf(f, "%-22s: %d\n", "page_size", 4096);I suspect this function doesn't work properly when page size is not 4K.> + > + virtio_cread_le(b->vdev, struct virtio_balloon_config, actual, > + &num_pages); > + /* Memory returned to host or amount we can inflate if possible */ > + seq_printf(f, "%-22s: %u\n", "ballooned_pages", num_pages);I don't really get the comment here.> + > + /* Total Memory for the guest from host */ > + seq_printf(f, "%-22s: %lu\n", "total_pages", i.totalram); > + > + /* Current memory for the guest */ > + seq_printf(f, "%-22s: %lu\n", "current_pages", i.totalram - num_pages);Are you sure these are in units of 4Kbyte pages?> + return 0; > +} > + > +DEFINE_SHOW_ATTRIBUTE(virtio_balloon_debug); > + > +static void virtio_balloon_debugfs_init(struct virtio_balloon *b) > +{ > + debugfs_create_file("virtio-balloon", 0444, NULL, b, > + &virtio_balloon_debug_fops); > +} > + > +static void virtio_balloon_debugfs_exit(struct virtio_balloon *b) > +{ > + debugfs_remove(debugfs_lookup("virtio-balloon", NULL)); > +} > + > +#else > + > +static inline void virtio_balloon_debugfs_init(struct virtio_balloon *b) > +{ > +} > + > +static inline void virtio_balloon_debugfs_exit(struct virtio_balloon *b) > +{ > +} > + > +#endif /* CONFIG_DEBUG_FS */ > + > #ifdef CONFIG_BALLOON_COMPACTION > /* > * virtballoon_migratepage - perform the balloon page migration on behalf of > @@ -1019,6 +1085,9 @@ static int virtballoon_probe(struct virtio_device *vdev) > > if (towards_target(vb)) > virtballoon_changed(vdev); > + > + virtio_balloon_debugfs_init(vb); > + > return 0; > > out_unregister_oom: > @@ -1065,6 +1134,8 @@ static void virtballoon_remove(struct virtio_device *vdev) > { > struct virtio_balloon *vb = vdev->priv; > > + virtio_balloon_debugfs_exit(vb); > + > if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) > page_reporting_unregister(&vb->pr_dev_info); > if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) > -- > 2.25.1