[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH] Disable virtio-balloon memory stats interface
From: |
Adam Litke |
Subject: |
Re: [Qemu-devel] [PATCH] Disable virtio-balloon memory stats interface |
Date: |
Tue, 14 Sep 2010 09:24:11 -0500 |
On Tue, 2010-09-14 at 11:09 -0300, Eduardo Habkost wrote:
> On Wed, Sep 08, 2010 at 09:21:16AM -0500, Adam Litke wrote:
> > The addition of memory stats reporting to the virtio balloon causes
> > the 'info balloon' command to become asynchronous. This is a regression
> > because in some cases it can hang the user monitor.
> >
> > Disable this feature until a better interface for asynchronous commands
> > can be worked out.
> >
> > Signed-off-by: Adam Litke <address@hidden>
> > ---
> > hw/virtio-balloon.c | 12 +++++++++++-
> > 1 files changed, 11 insertions(+), 1 deletions(-)
> >
> > diff --git a/hw/virtio-balloon.c b/hw/virtio-balloon.c
> > index 9fe3886..dcdada6 100644
> > --- a/hw/virtio-balloon.c
> > +++ b/hw/virtio-balloon.c
> > @@ -190,7 +190,17 @@ static void virtio_balloon_set_config(VirtIODevice
> > *vdev,
> >
> > static uint32_t virtio_balloon_get_features(VirtIODevice *vdev, uint32_t f)
> > {
> > - f |= (1 << VIRTIO_BALLOON_F_STATS_VQ);
> > + /*
> > + * The addition of memory stats reporting to the virtio balloon causes
> > + * the 'info balloon' command to become asynchronous. This is a
> > regression
> > + * because in some cases it can hang the user monitor.
> > + *
> > + * Disable this feature until a better interface for asynchronous
> > commands
> > + * can be worked out.
> > + *
> > + * -aglitke
> > + */
> > + /* f |= (1 << VIRTIO_BALLOON_F_STATS_VQ); */
>
>
> This field is guest-visible, won't this cause problems on migration?
I haven't followed migration very closely, but isn't this a common
problem whenever one migrates a vm to a newer version of qemu that has
more features. I thought that virtio feature negotiation would ensure
that stats have been disabled at the device level and would remain
disabled post migration. Please correct me if I am mistaken.
> Isn't it better to disable it on the "info balloon" side, so the guest
> knows that the host may start requesting stat info eventually? I suggest
> doing this:
While I think this method would also work, I would really like to use
the feature bit if possible, since that is what the mechanism is
designed for.
> ---
> diff --git a/hw/virtio-balloon.c b/hw/virtio-balloon.c
> index 1e4dfdd..92e9057 100644
> --- a/hw/virtio-balloon.c
> +++ b/hw/virtio-balloon.c
> @@ -30,6 +30,10 @@
> #include <sys/mman.h>
> #endif
>
> +/* Disable guest-provided stats by now (bz#623903, bz#626544) */
> +#define ENABLE_GUEST_STATS 0
> +
> +
> typedef struct VirtIOBalloon
> {
> VirtIODevice vdev;
> @@ -84,12 +88,14 @@ static QObject *get_stats_qobject(VirtIOBalloon *dev)
> VIRTIO_BALLOON_PFN_SHIFT);
>
> stat_put(dict, "actual", actual);
> +#if ENABLE_GUEST_STATS
> stat_put(dict, "mem_swapped_in", dev->stats[VIRTIO_BALLOON_S_SWAP_IN]);
> stat_put(dict, "mem_swapped_out", dev->stats[VIRTIO_BALLOON_S_SWAP_OUT]);
> stat_put(dict, "major_page_faults", dev->stats[VIRTIO_BALLOON_S_MAJFLT]);
> stat_put(dict, "minor_page_faults", dev->stats[VIRTIO_BALLOON_S_MINFLT]);
> stat_put(dict, "free_mem", dev->stats[VIRTIO_BALLOON_S_MEMFREE]);
> stat_put(dict, "total_mem", dev->stats[VIRTIO_BALLOON_S_MEMTOT]);
> +#endif
>
> return QOBJECT(dict);
> }
> @@ -215,7 +221,7 @@ static void virtio_balloon_to_target(void *opaque,
> ram_addr_t target,
> }
> dev->stats_callback = cb;
> dev->stats_opaque_callback_data = cb_data;
> - if (dev->vdev.guest_features & (1 << VIRTIO_BALLOON_F_STATS_VQ)) {
> + if (ENABLE_GUEST_STATS && (dev->vdev.guest_features & (1 <<
> VIRTIO_BALLOON_F_STATS_VQ))) {
> virtqueue_push(dev->svq, &dev->stats_vq_elem,
> dev->stats_vq_offset);
> virtio_notify(&dev->vdev, dev->svq);
> } else {
>
--
Thanks,
Adam
- [Qemu-devel] [PATCH] Disable virtio-balloon memory stats interface, Adam Litke, 2010/09/08
- Re: [Qemu-devel] [PATCH] Disable virtio-balloon memory stats interface, Eduardo Habkost, 2010/09/14
- Re: [Qemu-devel] [PATCH] Disable virtio-balloon memory stats interface,
Adam Litke <=
- Re: [Qemu-devel] [PATCH] Disable virtio-balloon memory stats interface, Eduardo Habkost, 2010/09/14
- Re: [Qemu-devel] [PATCH] Disable virtio-balloon memory stats interface, Eduardo Habkost, 2010/09/14
- Re: [Qemu-devel] [PATCH] Disable virtio-balloon memory stats interface, Luiz Capitulino, 2010/09/14
- Re: [Qemu-devel] [PATCH] Disable virtio-balloon memory stats interface, Adam Litke, 2010/09/14
- Re: [Qemu-devel] [PATCH] Disable virtio-balloon memory stats interface, Luiz Capitulino, 2010/09/14
Re: [Qemu-devel] [PATCH] Disable virtio-balloon memory stats interface, Adam Litke, 2010/09/14