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Re: [Qemu-devel] [PATCH v2] virtio-balloon: return empty data when no st
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH v2] virtio-balloon: return empty data when no stats are available |
Date: |
Wed, 21 May 2014 15:54:19 +0300 |
On Wed, May 21, 2014 at 11:03:47AM +0200, Ján Tomko wrote:
> If the guest hasn't updated the stats yet, instead of returning
> an error, return '-1' for the stats and '0' as 'last-update'.
>
> This lets applications ignore this without parsing the error message.
>
> Related libvirt patch and discussion:
> https://www.redhat.com/archives/libvir-list/2014-May/msg00460.html
>
> Tested against current upstream libvirt - stat reporting works and
> it no longer logs errors when the stats are queried on domain startup.
> (Note: libvirt doesn't use the last-update field for anything yet)
>
> Signed-off-by: Ján Tomko <address@hidden>
Applied, thanks!
> ---
> v1: https://lists.gnu.org/archive/html/qemu-devel/2014-05/msg03643.html
> Reviewed-by: Eric Blake <address@hidden>
> v2:
> rebased
> added documentation changes
> mentioned testing in the commit message
>
> docs/virtio-balloon-stats.txt | 5 +++--
> hw/virtio/virtio-balloon.c | 7 ++-----
> 2 files changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/docs/virtio-balloon-stats.txt b/docs/virtio-balloon-stats.txt
> index f74612f..edff5f2 100644
> --- a/docs/virtio-balloon-stats.txt
> +++ b/docs/virtio-balloon-stats.txt
> @@ -35,7 +35,8 @@ which will return a dictionary containing:
>
> o A key named last-update, which contains the last stats update
> timestamp in seconds. Since this timestamp is generated by the host,
> - a buggy guest can't influence its value
> + a buggy guest can't influence its value. The value is 0 if the guest
> + has not updated the stats (yet).
>
> It's also important to note the following:
>
> @@ -49,7 +50,7 @@ It's also important to note the following:
>
> - Polling can be enabled even if the guest doesn't have stats support
> or the balloon driver wasn't loaded in the guest. If this is the case
> - and stats are queried, an error will be returned
> + and stats are queried, last-update will be 0.
>
> - The polling timer is only re-armed when the guest responds to the
> statistics request. This means that if a (buggy) guest doesn't ever
> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> index bf2b588..22cd52e 100644
> --- a/hw/virtio/virtio-balloon.c
> +++ b/hw/virtio/virtio-balloon.c
> @@ -112,11 +112,6 @@ static void balloon_stats_get_all(Object *obj, struct
> Visitor *v,
> VirtIOBalloon *s = opaque;
> int i;
>
> - if (!s->stats_last_update) {
> - error_setg(errp, "guest hasn't updated any stats yet");
> - return;
> - }
> -
> visit_start_struct(v, NULL, "guest-stats", name, 0, &err);
> if (err) {
> goto out;
> @@ -378,6 +373,8 @@ static void virtio_balloon_device_realize(DeviceState
> *dev, Error **errp)
> s->dvq = virtio_add_queue(vdev, 128, virtio_balloon_handle_output);
> s->svq = virtio_add_queue(vdev, 128, virtio_balloon_receive_stats);
>
> + reset_stats(s);
> +
> register_savevm(dev, "virtio-balloon", -1, 1,
> virtio_balloon_save, virtio_balloon_load, s);
>
> --
> 1.8.3.2