migration: Extend query-migrate to provide dirty page limit info

Extend query-migrate to provide throttle time and estimated
ring full time with dirty-limit capability enabled, through which
we can observe if dirty limit take effect during live migration.

Signed-off-by: Hyman Huang(黄勇) <yong.huang@smartx.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Message-ID: <168733225273.5845.15871826788879741674-8@git.sr.ht>
Signed-off-by: Juan Quintela <quintela@redhat.com>

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

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);

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);
@@ -968,6 +969,15 @@ 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)

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 8.1)
+#
+# @dirty-limit-ring-full-time: Estimated average dirty ring full time (in microseconds)
+#                              each dirty ring full round, note that the value equals
+#                              dirty ring memory size divided by average dirty page rate
+#                              of virtual CPU, which can be used to observe the average
+#                              memory load of virtual CPU indirectly. Note that zero
+#                              means guest doesn't dirty memory (since 8.1)
+#
 # 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:

softmmu/dirtylimit.c

@@ -565,6 +565,45 @@ void hmp_set_vcpu_dirty_limit(Monitor *mon, const QDict *qdict)
     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;