migration: Introduce dirty-limit capability

Introduce migration dirty-limit capability, which can
be turned on before live migration and limit dirty
page rate durty live migration.

Introduce migrate_dirty_limit function to help check
if dirty-limit capability enabled during live migration.

Meanwhile, refactor vcpu_dirty_rate_stat_collect
so that period can be configured instead of hardcoded.

dirty-limit capability is kind of like auto-converge
but using dirty limit instead of traditional cpu-throttle
to throttle guest down. To enable this feature, turn on
the dirty-limit capability before live migration using
migrate-set-capabilities, and set the parameters
"x-vcpu-dirty-limit-period", "vcpu-dirty-limit" suitably
to speed up convergence.

Signed-off-by: Hyman Huang(黄勇) <yong.huang@smartx.com>
Acked-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Message-Id: <168618975839.6361.17407633874747688653-4@git.sr.ht>
Signed-off-by: Juan Quintela <quintela@redhat.com>

1 files changed, 14 insertions, 4 deletions

diff --git a/softmmu/dirtylimit.c b/softmmu/dirtylimit.c
index e802010..942d876 100644
--- a/softmmu/dirtylimit.c
+++ b/softmmu/dirtylimit.c
@@ -24,6 +24,9 @@
 #include "hw/boards.h"
 #include "sysemu/kvm.h"
 #include "trace.h"
+#include "migration/misc.h"
+#include "migration/migration.h"
+#include "migration/options.h"
 
 /*
  * Dirtylimit stop working if dirty page rate error
@@ -75,14 +78,21 @@ static bool dirtylimit_quit;
 
 static void vcpu_dirty_rate_stat_collect(void)
 {
+    MigrationState *s = migrate_get_current();
     VcpuStat stat;
     int i = 0;
+    int64_t period = DIRTYLIMIT_CALC_TIME_MS;
+
+    if (migrate_dirty_limit() &&
+        migration_is_active(s)) {
+        period = s->parameters.x_vcpu_dirty_limit_period;
+    }
 
     /* calculate vcpu dirtyrate */
-    vcpu_calculate_dirtyrate(DIRTYLIMIT_CALC_TIME_MS,
-                             &stat,
-                             GLOBAL_DIRTY_LIMIT,
-                             false);
+    vcpu_calculate_dirtyrate(period,
+                              &stat,
+                              GLOBAL_DIRTY_LIMIT,
+                              false);
 
     for (i = 0; i < stat.nvcpu; i++) {
         vcpu_dirty_rate_stat->stat.rates[i].id = i;