migration: Implement dirty-limit convergence algo

Implement dirty-limit convergence algo for live migration,
which is kind of like auto-converge algo but using dirty-limit
instead of cpu throttle to make migration convergent.

Enable dirty page limit if dirty_rate_high_cnt greater than 2
when dirty-limit capability enabled, Disable dirty-limit if
migration be canceled.

Note that "set_vcpu_dirty_limit", "cancel_vcpu_dirty_limit"
commands are not allowed during dirty-limit live migration.

Signed-off-by: Hyman Huang(黄勇) <yong.huang@smartx.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <168733225273.5845.15871826788879741674-7@git.sr.ht>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/softmmu/dirtylimit.c b/softmmu/dirtylimit.c
index 942d876523..a6d854d161 100644
--- a/softmmu/dirtylimit.c
+++ b/softmmu/dirtylimit.c
@@ -436,6 +436,23 @@ static void dirtylimit_cleanup(void)
     dirtylimit_state_finalize();
 }
 
+/*
+ * dirty page rate limit is not allowed to set if migration
+ * is running with dirty-limit capability enabled.
+ */
+static bool dirtylimit_is_allowed(void)
+{
+    MigrationState *ms = migrate_get_current();
+
+    if (migration_is_running(ms->state) &&
+        (!qemu_thread_is_self(&ms->thread)) &&
+        migrate_dirty_limit() &&
+        dirtylimit_in_service()) {
+        return false;
+    }
+    return true;
+}
+
 void qmp_cancel_vcpu_dirty_limit(bool has_cpu_index,
                                  int64_t cpu_index,
                                  Error **errp)
@@ -449,6 +466,12 @@ void qmp_cancel_vcpu_dirty_limit(bool has_cpu_index,
         return;
     }
 
+    if (!dirtylimit_is_allowed()) {
+        error_setg(errp, "can't cancel dirty page rate limit while"
+                   " migration is running");
+        return;
+    }
+
     if (!dirtylimit_in_service()) {
         return;
     }
@@ -499,6 +522,12 @@ void qmp_set_vcpu_dirty_limit(bool has_cpu_index,
         return;
     }
 
+    if (!dirtylimit_is_allowed()) {
+        error_setg(errp, "can't set dirty page rate limit while"
+                   " migration is running");
+        return;
+    }
+
     if (!dirty_rate) {
         qmp_cancel_vcpu_dirty_limit(has_cpu_index, cpu_index, errp);
         return;