[Qemu-devel] [RFC 10/29] migration: new property "x-postcopy-fast"

[Peter Xu]

This provides a way to start postcopy ASAP when migration starts. To do
this, we need both:

  -global migration.x-postcopy-ram=on \
  -global migration.x-postcopy-fast=on

Signed-off-by: Peter Xu <address@hidden>
---
 migration/migration.c | 9 ++++++++-
 migration/migration.h | 2 ++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/migration/migration.c b/migration/migration.c
index 5b2602e..efee87e 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1936,6 +1936,11 @@ bool migrate_colo_enabled(void)
     return s->enabled_capabilities[MIGRATION_CAPABILITY_X_COLO];
 }
 
+static bool postcopy_should_start(MigrationState *s)
+{
+    return atomic_read(&s->start_postcopy) || s->start_postcopy_fast;
+}
+
 /*
  * Master migration thread on the source VM.
  * It drives the migration and pumps the data down the outgoing channel.
@@ -2013,7 +2018,7 @@ static void *migration_thread(void *opaque)
                 if (migrate_postcopy_ram() &&
                     s->state != MIGRATION_STATUS_POSTCOPY_ACTIVE &&
                     pend_nonpost <= threshold_size &&
-                    atomic_read(&s->start_postcopy)) {
+                    postcopy_should_start(s)) {
 
                     if (!postcopy_start(s, &old_vm_running)) {
                         current_active_state = 
MIGRATION_STATUS_POSTCOPY_ACTIVE;
@@ -2170,6 +2175,8 @@ static Property migration_properties[] = {
                      send_configuration, true),
     DEFINE_PROP_BOOL("send-section-footer", MigrationState,
                      send_section_footer, true),
+    DEFINE_PROP_BOOL("x-postcopy-fast", MigrationState,
+                     start_postcopy_fast, false),
 
     /* Migration parameters */
     DEFINE_PROP_INT64("x-compress-level", MigrationState,
diff --git a/migration/migration.h b/migration/migration.h
index 70e3094..e902bae 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -113,6 +113,8 @@ struct MigrationState
 
     /* Flag set once the migration has been asked to enter postcopy */
     bool start_postcopy;
+    /* Set the flag if we want to start postcopy ASAP when migration starts */
+    bool start_postcopy_fast;
     /* Flag set after postcopy has sent the device state */
     bool postcopy_after_devices;
 
-- 
2.7.4