Re: [libvirt] [RFC PATCH] libvirt support to force convergence of live guest migration

On Thu, Nov 21, 2013 at 17:47:24 -0800, Chegu Vinod wrote: > Busy enterprise workloads hosted on large sized VM's tend to dirty > memory faster than the transfer rate achieved via live guest migration. > Despite some good recent improvements (& using dedicated 10Gig NICs > between hosts) the live migration may NOT converge. > > Recently support was added in qemu (version 1.6) to allow a user to > choose if they wish to force convergence of their migration via a > new migration capability : "auto-converge". This feature allows for qemu > to auto-detect lack of convergence and trigger a throttle-down of the > VCPUs. > > This RFC patch includes the libvirt support needed to trigger this > feature. (Testing is still in progress) > > Signed-off-by: Chegu Vinod <chegu_vinod(a)hp.com&gt; > --- > include/libvirt/libvirt.h.in | 1 + > src/qemu/qemu_migration.c | 44 ++++++++++++++++++++++++++++++++++++++++++ > src/qemu/qemu_migration.h | 1 + > src/qemu/qemu_monitor.c | 2 +- > src/qemu/qemu_monitor.h | 1 + > tools/virsh-domain.c | 7 ++++++ > 6 files changed, 55 insertions(+), 1 deletions(-) > > diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in > index 146a59b..13b0bfc 100644 > --- a/include/libvirt/libvirt.h.in > +++ b/include/libvirt/libvirt.h.in > @@ -1192,6 +1192,7 @@ typedef enum { > VIR_MIGRATE_OFFLINE = (1 << 10), /* offline migrate */ > VIR_MIGRATE_COMPRESSED = (1 << 11), /* compress data during migration */ > VIR_MIGRATE_ABORT_ON_ERROR = (1 << 12), /* abort migration on I/O errors happened during migration */ > + VIR_MIGRATE_AUTO_CONVERGE = (1 << 13), /* force auto-convergence during during migration */ > } virDomainMigrateFlags; I feel like there must be a better name we could use for this flag but I'm not able to come up with one... :-) > diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c > index e87ea85..8cc0c56 100644 > --- a/src/qemu/qemu_migration.c > +++ b/src/qemu/qemu_migration.c > @@ -1565,6 +1565,40 @@ cleanup: > } > > static int > +qemuMigrationSetAutoConverge(virQEMUDriverPtr driver, > + virDomainObjPtr vm, > + enum qemuDomainAsyncJob job) Nicely copied&pasted from qemuMigrationSetCompression but you forgot to fix indentation :-)

> +{ > + qemuDomainObjPrivatePtr priv = vm->privateData; > + int ret; > + > + if (qemuDomainObjEnterMonitorAsync(driver, vm, job) < 0) > + return -1; > + > + ret = qemuMonitorGetMigrationCapability( > + priv->mon, > + QEMU_MONITOR_MIGRATION_CAPS_AUTO_CONVERGE); > + > + if (ret < 0) { > + goto cleanup; > + } else if (ret == 0) { > + virReportError(VIR_ERR_ARGUMENT_UNSUPPORTED, "%s", > + _("Auto-Converge migration is not supported by " > + "QEMU binary")); Reduce indentation by one level. Also I think "migration" is not really needed in the error message, I'd just change it to "Auto-converge is not supported by QEMU binary".

> + ret = -1; > + goto cleanup; > + } > + > + ret = qemuMonitorSetMigrationCapability( > + priv->mon, > + QEMU_MONITOR_MIGRATION_CAPS_AUTO_CONVERGE); > + > +cleanup: > + qemuDomainObjExitMonitor(driver, vm); > + return ret; > +} > + > +static int > qemuMigrationWaitForSpice(virQEMUDriverPtr driver, > virDomainObjPtr vm) > { > @@ -2389,6 +2423,11 @@ qemuMigrationPrepareAny(virQEMUDriverPtr driver, > QEMU_ASYNC_JOB_MIGRATION_IN) < 0) > goto stop; > > + if (flags & VIR_MIGRATE_AUTO_CONVERGE && > + qemuMigrationSetAutoConverge(driver, vm, > + QEMU_ASYNC_JOB_MIGRATION_IN) < 0) > + goto stop; > + Hmm, I know you are just following what I did with VIR_MIGRATE_COMPRESSED, but setting auto-converge on destination doesn't make any sense. And it doesn't even make a lot of sense to set compression on destination (other than checking the destination supports compression) so I'm wondering why I did so. > if (mig->lockState) { > VIR_DEBUG("Received lockstate %s", mig->lockState); > VIR_FREE(priv->lockState); > @@ -3181,6 +3220,11 @@ qemuMigrationRun(virQEMUDriverPtr driver, > QEMU_ASYNC_JOB_MIGRATION_OUT) < 0) > goto cleanup; > > + if (flags & VIR_MIGRATE_AUTO_CONVERGE && > + qemuMigrationSetAutoConverge(driver, vm, > + QEMU_ASYNC_JOB_MIGRATION_OUT) < 0) Indentation is off by one space.

> + goto cleanup; > + > if (qemuDomainObjEnterMonitorAsync(driver, vm, > QEMU_ASYNC_JOB_MIGRATION_OUT) < 0) > goto cleanup; ... So except for the small issues, the patch looks good to me. However, do I remember correctly that this feature can be turned on dynamically for an already running migration? If so, I think we want a second patch adding a new API for setting this auto-converge feature.

Jirka .