commit ef1065cf5acad13767c054758cbe7f4e8af5d241
Author: Jim Fehlig <jfehlig@novell.com>
Date:   Fri Aug 26 12:10:26 2011 -0600

    Set qemu migration speed unlimited when migrating to file
    
    The qemu migration speed default is 32MiB/s as defined in migration.c
    
    /* Migration speed throttling */
    static int64_t max_throttle = (32 << 20);
    
    There's no need to throttle migration when targeting a file, so set migration
    speed to unlimited prior to migration, and restore to libvirt default value
    after migration.
    
    Default units is MB for migrate_set_speed monitor command, so
    (INT64_MAX / (1024 * 1024)) is used for unlimited migration speed.
    
    Tested with both json and text monitors.

Index: libvirt-0.9.4/src/qemu/qemu_migration.c
===================================================================
--- libvirt-0.9.4.orig/src/qemu/qemu_migration.c
+++ libvirt-0.9.4/src/qemu/qemu_migration.c
@@ -2675,6 +2675,16 @@ qemuMigrationToFile(struct qemud_driver
     bool restoreLabel = false;
     virCommandPtr cmd = NULL;
     int pipeFD[2] = { -1, -1 };
+    unsigned long saveMigBandwidth = priv->migMaxBandwidth;
+
+    /* Increase migration bandwidth to unlimited since target is a file.
+     * Failure to change migration speed is not fatal. */
+    if (qemuDomainObjEnterMonitorAsync(driver, vm, asyncJob) == 0) {
+        qemuMonitorSetMigrationSpeed(priv->mon,
+                                     QEMU_DOMAIN_FILE_MIG_BANDWIDTH_MAX);
+        priv->migMaxBandwidth = QEMU_DOMAIN_FILE_MIG_BANDWIDTH_MAX;
+        qemuDomainObjExitMonitorWithDriver(driver, vm);
+    }
 
     if (qemuCapsGet(priv->qemuCaps, QEMU_CAPS_MIGRATE_QEMU_FD) &&
         (!compressor || pipe(pipeFD) == 0)) {
@@ -2783,6 +2793,13 @@ qemuMigrationToFile(struct qemud_driver
     ret = 0;
 
 cleanup:
+    /* Restore max migration bandwidth */
+    if (qemuDomainObjEnterMonitorAsync(driver, vm, asyncJob) == 0) {
+        qemuMonitorSetMigrationSpeed(priv->mon, saveMigBandwidth);
+        priv->migMaxBandwidth = saveMigBandwidth;
+        qemuDomainObjExitMonitorWithDriver(driver, vm);
+    }
+
     VIR_FORCE_CLOSE(pipeFD[0]);
     VIR_FORCE_CLOSE(pipeFD[1]);
     virCommandFree(cmd);