Re: [PATCH] qemu: process: Improve update of maximum baloon state at startup

[Martin Kletzander <mkletzan@xxxxxxxxxx>]

On Tue, Jun 30, 2015 at 04:38:13PM +0200, Peter Krempa wrote:
> In commit 641a145d73fdc3dd9350fd57b3d3247abf101c05 I've added code that
> resets the ballon memory value to full size prior to resuming the vCPUs
> since the size certainly was not reduced at that point.
>
> Since qemuProcess start is used also in code paths with already booted
> up guests (migration, save/restore) the assumption is not entirely true
> since the guest might already been running before.
>
> This patch adds a function that queries the monitor rather than using
> the full size since a balloon event would not be reissued in case we are
> recovering a saved migration state.
>
> Additionally the new function is used also when reconnecting to a VM
> after libvirtd restart since we might have missed a few ballon events
> while libvirtd was not running.
> ---
> src/qemu/qemu_process.c | 35 ++++++++++++++++++++++++++++++++++-
> 1 file changed, 34 insertions(+), 1 deletion(-)
>
> diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
> index ba84182..5698404 100644
> --- a/src/qemu/qemu_process.c
> +++ b/src/qemu/qemu_process.c
> @@ -2065,6 +2065,35 @@ qemuProcessReconnectRefreshChannelVirtioState(virQEMUDriverPtr driver,
>
>
> static int
> +qemuProcessRefreshBallonState(virQEMUDriverPtr driver,
> +                              virDomainObjPtr vm)

Shouldn't this also accept int asyncJob parameter so that it works
similarly to qemuProcessUpdateVideoRamSize() in the qemuProcessStart()?

> +{
> +    unsigned long long balloon;
> +    int rc;
> +
> +    /* if no balloning is available, the current size equals to the current
> +     * full memory size */
> +    if (!vm->def->memballoon ||
> +        vm->def->memballoon->model == VIR_DOMAIN_MEMBALLOON_MODEL_NONE) {
> +        vm->def->mem.cur_balloon = virDomainDefGetMemoryActual(vm->def);
> +        return 0;
> +    }
> +
> +    qemuDomainObjEnterMonitor(driver, vm);
> +    rc = qemuMonitorGetBalloonInfo(qemuDomainGetMonitor(vm), &balloon);
> +    if (qemuDomainObjExitMonitor(driver, vm) < 0)
> +        rc = -1;
> +
> +    if (rc < 0)
> +        return -1;
> +
> +    vm->def->mem.cur_balloon = balloon;
> +
> +    return 0;
> +}
> +
> +
> +static int
> qemuProcessWaitForMonitor(virQEMUDriverPtr driver,
>                           virDomainObjPtr vm,
>                           int asyncJob,
> @@ -3779,6 +3808,9 @@ qemuProcessReconnect(void *opaque)
>     if (qemuProcessReconnectRefreshChannelVirtioState(driver, obj) < 0)
>         goto error;
>
> +    if (qemuProcessRefreshBallonState(driver, obj) < 0)
> +        goto error;
> +
>     if (qemuProcessRecoverJob(driver, obj, conn, &oldjob) < 0)
>         goto error;
>
> @@ -4922,7 +4954,8 @@ int qemuProcessStart(virConnectPtr conn,
>     /* Since CPUs were not started yet, the ballon could not return the memory
>      * to the host and thus cur_balloon needs to be updated so that GetXMLdesc
>      * and friends return the correct size in case they can't grab the job */
> -    vm->def->mem.cur_balloon = virDomainDefGetMemoryActual(vm->def);
> +    if (qemuProcessRefreshBallonState(driver, vm) < 0)
> +        goto cleanup;
>
>     VIR_DEBUG("Detecting actual memory size for video device");
>     if (qemuProcessUpdateVideoRamSize(driver, vm, asyncJob) < 0)
> --
> 2.4.1
>
> --
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