On Tue, Dec 04, 2012 at 01:04:47PM -0200, Luiz Capitulino wrote:
> The statistics are now available through device properties via a
> polling mechanism. First, a client has to enable polling, then it
> can query the stats.
>
> The following control properties are introduced:
>
> o stats-polling-interval: a value greater than zero enables polling
> in the specified interval (in seconds). When value equals zero,
> polling is disabled. If polling is already enabled and a value
> greater than zero is written, the polling interval time is changed
>
> o stats-last-update: last stats update timestamp, in seconds.
>
> The following stats properties are introduced:
>
> o stat-swap-in
> o stat-swap-out
> o stat-major-faults
> o stat-minor-faults
> o stat-free-memory
> o stat-total-memory
>
> All values are in bytes. A value of -1 means that the statistic isn't
> available right now.
>
> FIXME: Can balloon_stats_poll_cb(), balloon_stats_set_poll_interval(),
> virtio_balloon_handle_output() can run in parallel?
>
> XXX: Should we return an error instead of -1? Might require a specific
> error. Although this is not exactly a failure...
>
> Signed-off-by: Luiz Capitulino <lcapitul...@redhat.com>
> ---
>
> NOTE: Anthony suggested having a bool to enable/disable polling, but I prefer
> to let the client specify the polling interval. I can revisit this,
> though.
>
> hw/virtio-balloon.c | 156
> +++++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 155 insertions(+), 1 deletion(-)
>
> diff --git a/hw/virtio-balloon.c b/hw/virtio-balloon.c
> index 4398025..06af18f 100644
> --- a/hw/virtio-balloon.c
> +++ b/hw/virtio-balloon.c
> @@ -22,6 +22,8 @@
> #include "virtio-balloon.h"
> #include "kvm.h"
> #include "exec-memory.h"
> +#include "qemu-timer.h"
> +#include "qapi/qapi-visit-core.h"
>
> #if defined(__linux__)
> #include <sys/mman.h>
> @@ -36,6 +38,9 @@ typedef struct VirtIOBalloon
> uint64_t stats[VIRTIO_BALLOON_S_NR];
> VirtQueueElement stats_vq_elem;
> size_t stats_vq_offset;
> + QEMUTimer *stats_timer;
> + int64_t stats_last_update;
> + int64_t stats_poll_interval;
> DeviceState *qdev;
> } VirtIOBalloon;
>
> @@ -53,6 +58,16 @@ static void balloon_page(void *addr, int deflate)
> #endif
> }
>
> +static const char *balloon_stat_names[] = {
> + [VIRTIO_BALLOON_S_SWAP_IN] = "stat-swap-in",
> + [VIRTIO_BALLOON_S_SWAP_OUT] = "stat-swap-out",
> + [VIRTIO_BALLOON_S_MAJFLT] = "stat-major-faults",
> + [VIRTIO_BALLOON_S_MINFLT] = "stat-minor-faults",
> + [VIRTIO_BALLOON_S_MEMFREE] = "stat-free-memory",
> + [VIRTIO_BALLOON_S_MEMTOT] = "stat-total-memory",
> + [VIRTIO_BALLOON_S_NR] = NULL
> +};
> +
> /*
> * reset_stats - Mark all items in the stats array as unset
> *
> @@ -67,6 +82,119 @@ static inline void reset_stats(VirtIOBalloon *dev)
> for (i = 0; i < VIRTIO_BALLOON_S_NR; dev->stats[i++] = -1);
> }
>
> +static bool balloon_stats_supported(const VirtIOBalloon *s)
> +{
> + return s->vdev.guest_features & (1 << VIRTIO_BALLOON_F_STATS_VQ);
> +}
> +
> +static bool balloon_stats_enabled(const VirtIOBalloon *s)
> +{
> + return s->stats_poll_interval > 0;
> +}
> +
> +static void balloon_stats_disable_timer(VirtIOBalloon *s)
> +{
> + if (balloon_stats_enabled(s)) {
> + qemu_del_timer(s->stats_timer);
> + qemu_free_timer(s->stats_timer);
> + s->stats_timer = NULL;
> + s->stats_poll_interval = 0;
> + }
> +}
> +
> +static void balloon_stats_change_timer(VirtIOBalloon *s, int secs)
> +{
> + qemu_mod_timer(s->stats_timer, qemu_get_clock_ms(vm_clock) + secs *
> 1000);
> +}
> +
> +static void balloon_stats_poll_cb(void *opaque)
> +{
> + VirtIOBalloon *s = opaque;
> +
> + virtqueue_push(s->svq, &s->stats_vq_elem, s->stats_vq_offset);
> + virtio_notify(&s->vdev, s->svq);
I think we'll want to add some logic to avoid the potential for
re-pushing an elem we've already processed, as I think that violates the
virtio spec. In the past the monitor blocked us from doing this but with
timer-driven requests I think it's a possibility now.
But the general approach seems sane to me and the code looks to
be in decent shape.
> --
> 1.8.0
>
>
