On Tue, Jul 02, 2013 at 09:39:23AM -0400, John Ferlan wrote:
> At vm startup, reconnect, and attach - check for the presence of the balloon
> driver and save the path in the private area of the driver. This path will
> remain constant throughout the life of the domain and can then be used rather
> than attempting to find the path each time balloon driver statistics are
> fetched or the collection period changes. The qom object model model requires
> setting object properties after device startup. That is, it's not possible
> to pass the period along via the startup code as it won't be recognized.
> If a balloon driver path is found a check of the existing collection period
> will be made against the saved domain value in order to determine if an
> adjustment needs to be made to the period to start or stop collecting stats
> ---
> src/qemu/qemu_domain.c | 1 +
> src/qemu/qemu_domain.h | 2 +
> src/qemu/qemu_process.c | 164 +++++++++++++++++++++++++++++++++++++++++++++++-
> 3 files changed, 165 insertions(+), 2 deletions(-)
>
> diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
> index 8d79066..5aaf1e1 100644
> --- a/src/qemu/qemu_domain.c
> +++ b/src/qemu/qemu_domain.c
> @@ -244,6 +244,7 @@ qemuDomainObjPrivateFree(void *data)
> VIR_FREE(priv->vcpupids);
> VIR_FREE(priv->lockState);
> VIR_FREE(priv->origname);
> + VIR_FREE(priv->balloonpath);
>
> virChrdevFree(priv->devs);
>
> diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h
> index 068a4c3..005fd0f 100644
> --- a/src/qemu/qemu_domain.h
> +++ b/src/qemu/qemu_domain.h
> @@ -161,6 +161,8 @@ struct _qemuDomainObjPrivate {
> char *origname;
> int nbdPort; /* Port used for migration with NBD */
>
> + char *balloonpath;
> +
> virChrdevsPtr devs;
I think I'd prefer this to be kept as a private property
in the struct qemuMonitor.
> diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
> index ac5ffcf..9a2add1 100644
> --- a/src/qemu/qemu_process.c
> +++ b/src/qemu/qemu_process.c
> @@ -1564,6 +1564,150 @@ qemuProcessLookupPTYs(virDomainChrDefPtr *devices,
> return 0;
> }
>
> +/* Search the qom objects for the balloon driver object by it's known name
> + * of "virtio-balloon-pci". The entry for the driver will be found in the
> + * returned 'type' field using the syntax "child<virtio-balloon-pci>".
> + *
> + * Once found, check the entry to ensure it has the correct property listed.
> + * If it does not, then obtaining statistics from qemu will not be possible.
> + * This feature was added to qemu 1.5.
> + *
> + * This procedure will be call recursively until found or the qom-list is
> + * exhausted.
> + *
> + * Returns:
> + *
> + * 1 - Found
> + * 0 - Not found still looking
> + * -1 - Error bail out
> + *
> + * NOTE: This assumes we have already called qemuDomainObjEnterMonitor()
> + */
> +static int
> +qemuProcessFindBalloonObjectPath(qemuMonitorPtr mon,
> + virDomainObjPtr vm,
> + const char *curpath,
> + char **balloonpath)
> +{
> + int i,j;
> + int npaths = 0;
> + int nprops = 0;
> + int ret = 0;
> + char *nextpath = NULL;
> + qemuMonitorListPathPtr *paths = NULL;
> + qemuMonitorListPathPtr *bprops = NULL;
> +
> + /* Not supported */
> + if (vm->def->memballoon &&
> + vm->def->memballoon->model != VIR_DOMAIN_MEMBALLOON_MODEL_VIRTIO) {
> + VIR_DEBUG("Model must be virtio to get memballoon path");
> + return -1;
> + }
> +
> + /* Already set and won't change */
> + if (*balloonpath)
> + return 1;
> +
> + VIR_DEBUG("Searching for Balloon Object Path starting at %s", curpath);
> +
> + npaths = qemuMonitorGetObjectListPaths(mon, curpath, &paths);
> +
> + for (i = 0; i < npaths && ret == 0; i++) {
> +
> + if (STREQ_NULLABLE(paths[i]->type, "link<virtio-balloon-pci>")) {
> + VIR_DEBUG("Path to <virtio-balloon-pci> is '%s/%s'",
> + curpath, paths[i]->name);
> + if (virAsprintf(&nextpath, "%s/%s", curpath, paths[i]->name) < 0) {
> + ret = -1;
> + goto cleanup;
> + }
> +
> + /* Now look at the each of the property entries to determine
> + * whether "guest-stats-polling-interval" exists. If not,
> + * then this version of qemu/kvm does not support the feature.
> + */
> + nprops = qemuMonitorGetObjectListPaths(mon, nextpath, &bprops);
> + for (j = 0; j < nprops; j++) {
> + if (STREQ(bprops[j]->name, "guest-stats-polling-interval")) {
> + *balloonpath = nextpath;
> + nextpath = NULL;
> + ret = 1;
> + goto cleanup;
> + }
> + }
> +
> + /* If we get here, we found the path, but not the property */
> + VIR_DEBUG("Property 'guest-stats-polling-interval' not found");
> + ret = -1;
> + goto cleanup;
> + }
> +
> + /* Type entries that begin with "child<" are a branch that can be
> + * traversed looking for more entries
> + */
> + if (paths[i]->type && STRPREFIX(paths[i]->type, "child<")) {
> + if (virAsprintf(&nextpath, "%s/%s", curpath, paths[i]->name) < 0) {
> + virReportOOMError();
> + ret = -1;
> + goto cleanup;
> + }
> + ret = qemuProcessFindBalloonObjectPath(mon, vm, nextpath,
> + balloonpath);
> + }
> + }
> +
> +cleanup:
> + for (i = 0; i < npaths; i++)
> + qemuMonitorListPathFree(paths[i]);
> + VIR_FREE(paths);
> + for (j = 0; j < nprops; j++)
> + qemuMonitorListPathFree(bprops[j]);
> + VIR_FREE(bprops);
> + VIR_FREE(nextpath);
> + return ret;
> +}
I think this method should be kept in qemu_monitor.c and made static
to that file
We can then populate it on first use.
> +/*
> + * Using the provided balloonpath, determine if we need to set the
> + * collection interval property to enable statistics gathering.
> + *
> + * NOTE: This assumes we have already called qemuDomainObjEnterMonitor()
> + */
> +static void
> +qemuProcessUpdateBalloonStatsPeriod(qemuMonitorPtr mon,
> + char *balloonpath,
> + virDomainObjPtr vm)
> +{
> + qemuMonitorObjectProperty prop;
> +
> + /* Get the current value of the stats polling interval */
> + memset(&prop, 0, sizeof(qemuMonitorObjectProperty));
> + prop.type = QEMU_MONITOR_OBJECT_PROPERTY_INT;
> + if (qemuMonitorGetObjectProperty(mon, balloonpath,
> + "guest-stats-polling-interval",
> + &prop) < 0) {
> + VIR_DEBUG("Failed to get polling interval for balloon driver");
> + return;
> + }
> +
> + VIR_DEBUG("memballoon period=%d 'guest-stats-polling-interval'=%d",
> + vm->def->memballoon->period, prop.val.i);
> +
> + /* Same value - no need to set */
> + if (vm->def->memballoon->period == prop.val.i)
> + return;
> +
> + /* Set to the value in memballoon (could enable or disable) */
> + memset(&prop, 0, sizeof(qemuMonitorObjectProperty));
> + prop.type = QEMU_MONITOR_OBJECT_PROPERTY_INT;
> + prop.val.i = vm->def->memballoon->period;
> + if (qemuMonitorSetObjectProperty(mon, balloonpath,
> + "guest-stats-polling-interval",
> + &prop) < 0)
> + VIR_DEBUG("Failed to set polling interval for balloon driver");
> +
> +}
Since I recommended that we don't expose qemuMonitorGetObjectProperty
or qemuMonitorSetObjectProperty in qemu_monitor.h, what you'll need
todo here is move this code into qemu_monitor.c defining a method
something like
int qemuMonitorSetBalloonStatsPeriod(qemuMonitorPtr mon,
int period);
This method can populate the balloonpath field in qemuMOnitorPtr struct
on first use.
Regards,
Daniel
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