Subject: [PATCH v2] libvirt support to force convergence of live guest migration

Changes since RFC (i.e. v1) patch :
- Incorporated feedback from Jiri Denemark

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 patch includes the libvirt support needed to trigger this
feature. (Testing is in progress)

Signed-off-by:  Chegu Vinod <chegu_vinod@hp.com>
---
 include/libvirt/libvirt.h.in |  1 +
 src/qemu/qemu_migration.c    | 40 ++++++++++++++++++++++++++++++++++++++++
 src/qemu/qemu_migration.h    |  3 ++-
 src/qemu/qemu_monitor.c      |  2 +-
 src/qemu/qemu_monitor.h      |  1 +
 tools/virsh-domain.c         |  7 +++++++
 6 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in
index 295d551..c0fc08b 100644
--- a/include/libvirt/libvirt.h.in
+++ b/include/libvirt/libvirt.h.in
@@ -1200,6 +1200,7 @@ 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 convergence */
 } virDomainMigrateFlags;
 
 
diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
index 407fb70..379d19b 100644
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -1565,6 +1565,41 @@ cleanup:
 }
 
 static int
+qemuMigrationSetAutoConverge(virQEMUDriverPtr driver,
+                             virDomainObjPtr vm,
+                             enum qemuDomainAsyncJob job)
+{
+    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 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)
 {
@@ -3175,6 +3210,11 @@ 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)
+        goto cleanup;
+
     if (qemuDomainObjEnterMonitorAsync(driver, vm,
                                        QEMU_ASYNC_JOB_MIGRATION_OUT) < 0)
         goto cleanup;
diff --git a/src/qemu/qemu_migration.h b/src/qemu/qemu_migration.h
index cafa2a2..a802fb7 100644
--- a/src/qemu/qemu_migration.h
+++ b/src/qemu/qemu_migration.h
@@ -39,7 +39,8 @@
      VIR_MIGRATE_UNSAFE |                       \
      VIR_MIGRATE_OFFLINE |                      \
      VIR_MIGRATE_COMPRESSED |                   \
-     VIR_MIGRATE_ABORT_ON_ERROR)
+     VIR_MIGRATE_ABORT_ON_ERROR |               \
+     VIR_MIGRATE_AUTO_CONVERGE)
 
 /* All supported migration parameters and their types. */
 # define QEMU_MIGRATION_PARAMETERS                              \
diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c
index a2769db..201f60c 100644
--- a/src/qemu/qemu_monitor.c
+++ b/src/qemu/qemu_monitor.c
@@ -118,7 +118,7 @@ VIR_ENUM_IMPL(qemuMonitorMigrationStatus,
 
 VIR_ENUM_IMPL(qemuMonitorMigrationCaps,
               QEMU_MONITOR_MIGRATION_CAPS_LAST,
-              "xbzrle")
+              "xbzrle", "auto-converge")
 
 VIR_ENUM_IMPL(qemuMonitorVMStatus,
               QEMU_MONITOR_VM_STATUS_LAST,
diff --git a/src/qemu/qemu_monitor.h b/src/qemu/qemu_monitor.h
index eabf000..95e70ab 100644
--- a/src/qemu/qemu_monitor.h
+++ b/src/qemu/qemu_monitor.h
@@ -440,6 +440,7 @@ int qemuMonitorGetSpiceMigrationStatus(qemuMonitorPtr mon,
 
 typedef enum {
     QEMU_MONITOR_MIGRATION_CAPS_XBZRLE,
+    QEMU_MONITOR_MIGRATION_CAPS_AUTO_CONVERGE,
 
     QEMU_MONITOR_MIGRATION_CAPS_LAST
 } qemuMonitorMigrationCaps;
diff --git a/tools/virsh-domain.c b/tools/virsh-domain.c
index c3db94c..d319ba7 100644
--- a/tools/virsh-domain.c
+++ b/tools/virsh-domain.c
@@ -8628,6 +8628,10 @@ static const vshCmdOptDef opts_migrate[] = {
      .type = VSH_OT_BOOL,
      .help = N_("compress repeated pages during live migration")
     },
+    {.name = "auto-converge",
+     .type = VSH_OT_BOOL,
+     .help = N_("force convergence during live migration")
+    },
     {.name = "abort-on-error",
      .type = VSH_OT_BOOL,
      .help = N_("abort on soft errors during migration")
@@ -8772,6 +8776,9 @@ doMigrate(void *opaque)
     if (vshCommandOptBool(cmd, "compressed"))
         flags |= VIR_MIGRATE_COMPRESSED;
 
+    if (vshCommandOptBool(cmd, "auto-converge"))
+        flags |= VIR_MIGRATE_AUTO_CONVERGE;
+
     if (vshCommandOptBool(cmd, "offline")) {
         flags |= VIR_MIGRATE_OFFLINE;
     }
-- 
1.8.3.1