[QEMU,v10,8/9] migration: Extend query-migrate to provide dirty-limit info

diff --git a/include/sysemu/dirtylimit.h b/include/sysemu/dirtylimit.h
index 8d2c1f3a6b..d11ebbbbdb 100644
--- a/include/sysemu/dirtylimit.h
+++ b/include/sysemu/dirtylimit.h
@@ -34,4 +34,6 @@  void dirtylimit_set_vcpu(int cpu_index,
 void dirtylimit_set_all(uint64_t quota,
                         bool enable);
 void dirtylimit_vcpu_execute(CPUState *cpu);
+uint64_t dirtylimit_throttle_time_per_round(void);
+uint64_t dirtylimit_ring_full_time(void);
 #endif
diff --git a/migration/migration-hmp-cmds.c b/migration/migration-hmp-cmds.c
index 35e8020bbf..c115ef2d23 100644
--- a/migration/migration-hmp-cmds.c
+++ b/migration/migration-hmp-cmds.c
@@ -190,6 +190,16 @@  void hmp_info_migrate(Monitor *mon, const QDict *qdict)
                        info->cpu_throttle_percentage);
     }
 
+    if (info->has_dirty_limit_throttle_time_per_round) {
+        monitor_printf(mon, "dirty-limit throttle time: %" PRIu64 " us\n",
+                       info->dirty_limit_throttle_time_per_round);
+    }
+
+    if (info->has_dirty_limit_ring_full_time) {
+        monitor_printf(mon, "dirty-limit ring full time: %" PRIu64 " us\n",
+                       info->dirty_limit_ring_full_time);
+    }
+
     if (info->has_postcopy_blocktime) {
         monitor_printf(mon, "postcopy blocktime: %u\n",
                        info->postcopy_blocktime);
diff --git a/migration/migration.c b/migration/migration.c
index 619af62461..3b8587c4ae 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -64,6 +64,7 @@ 
 #include "yank_functions.h"
 #include "sysemu/qtest.h"
 #include "options.h"
+#include "sysemu/dirtylimit.h"
 
 static NotifierList migration_state_notifiers =
     NOTIFIER_LIST_INITIALIZER(migration_state_notifiers);
@@ -974,6 +975,15 @@  static void populate_ram_info(MigrationInfo *info, MigrationState *s)
         info->ram->dirty_pages_rate =
            stat64_get(&mig_stats.dirty_pages_rate);
     }
+
+    if (migrate_dirty_limit() && dirtylimit_in_service()) {
+        info->has_dirty_limit_throttle_time_per_round = true;
+        info->dirty_limit_throttle_time_per_round =
+                            dirtylimit_throttle_time_per_round();
+
+        info->has_dirty_limit_ring_full_time = true;
+        info->dirty_limit_ring_full_time = dirtylimit_ring_full_time();
+    }
 }
 
 static void populate_disk_info(MigrationInfo *info)
diff --git a/qapi/migration.json b/qapi/migration.json
index b4d9100ef3..7bf4b30614 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -250,6 +250,18 @@ 
 #     blocked.  Present and non-empty when migration is blocked.
 #     (since 6.0)
 #
+# @dirty-limit-throttle-time-per-round: Maximum throttle time
+#     (in microseconds) of virtual CPUs each dirty ring full round,
+#     which shows how MigrationCapability dirty-limit affects the
+#     guest during live migration.  (Since 8.2)
+#
+# @dirty-limit-ring-full-time: Estimated average dirty ring full
+#     time (in microseconds) each dirty ring full round. The value
+#     equals dirty ring memory size divided by average dirty page
+#     rate of the virtual CPU, which can be used to observe the
+#     average memory load of the virtual CPU indirectly. Note that
+#     zero means guest doesn't dirty memory.  (Since 8.2)
+#
 # Since: 0.14
 ##
 { 'struct': 'MigrationInfo',
@@ -267,7 +279,9 @@ 
            '*postcopy-blocktime' : 'uint32',
            '*postcopy-vcpu-blocktime': ['uint32'],
            '*compression': 'CompressionStats',
-           '*socket-address': ['SocketAddress'] } }
+           '*socket-address': ['SocketAddress'],
+           '*dirty-limit-throttle-time-per-round': 'uint64',
+           '*dirty-limit-ring-full-time': 'uint64'} }
 
 ##
 # @query-migrate:
diff --git a/softmmu/dirtylimit.c b/softmmu/dirtylimit.c
index 5134296667..a0686323e5 100644
--- a/softmmu/dirtylimit.c
+++ b/softmmu/dirtylimit.c
@@ -565,6 +565,45 @@  out:
     hmp_handle_error(mon, err);
 }
 
+/* Return the max throttle time of each virtual CPU */
+uint64_t dirtylimit_throttle_time_per_round(void)
+{
+    CPUState *cpu;
+    int64_t max = 0;
+
+    CPU_FOREACH(cpu) {
+        if (cpu->throttle_us_per_full > max) {
+            max = cpu->throttle_us_per_full;
+        }
+    }
+
+    return max;
+}
+
+/*
+ * Estimate average dirty ring full time of each virtaul CPU.
+ * Return 0 if guest doesn't dirty memory.
+ */
+uint64_t dirtylimit_ring_full_time(void)
+{
+    CPUState *cpu;
+    uint64_t curr_rate = 0;
+    int nvcpus = 0;
+
+    CPU_FOREACH(cpu) {
+        if (cpu->running) {
+            nvcpus++;
+            curr_rate += vcpu_dirty_rate_get(cpu->cpu_index);
+        }
+    }
+
+    if (!curr_rate || !nvcpus) {
+        return 0;
+    }
+
+    return dirtylimit_dirty_ring_full_time(curr_rate / nvcpus);
+}
+
 static struct DirtyLimitInfo *dirtylimit_query_vcpu(int cpu_index)
 {
     DirtyLimitInfo *info = NULL;