[v4,4/8] migration: expose xbzrle cache miss rate

diff --git a/arch_init.c b/arch_init.c
index a7c87de..15ca4c0 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -235,6 +235,7 @@  typedef struct AccountingInfo {
     uint64_t xbzrle_bytes;
     uint64_t xbzrle_pages;
     uint64_t xbzrle_cache_miss;
+    double xbzrle_cache_miss_rate;
     uint64_t xbzrle_overflows;
 } AccountingInfo;
 
@@ -290,6 +291,11 @@  uint64_t xbzrle_mig_pages_cache_miss(void)
     return acct_info.xbzrle_cache_miss;
 }
 
+double xbzrle_mig_cache_miss_rate(void)
+{
+    return acct_info.xbzrle_cache_miss_rate;
+}
+
 uint64_t xbzrle_mig_pages_overflow(void)
 {
     return acct_info.xbzrle_overflows;
@@ -488,6 +494,8 @@  static void migration_bitmap_sync(void)
     static int64_t num_dirty_pages_period;
     int64_t end_time;
     int64_t bytes_xfer_now;
+    static uint64_t xbzrle_cache_miss_prev;
+    static uint64_t iterations_prev;
 
     bitmap_sync_count++;
 
@@ -531,6 +539,16 @@  static void migration_bitmap_sync(void)
         } else {
              mig_throttle_on = false;
         }
+        if (migrate_use_xbzrle()) {
+            if (iterations_prev != 0) {
+                acct_info.xbzrle_cache_miss_rate =
+                   (double)(acct_info.xbzrle_cache_miss -
+                            xbzrle_cache_miss_prev) /
+                   (acct_info.iterations - iterations_prev);
+            }
+            iterations_prev = acct_info.iterations;
+            xbzrle_cache_miss_prev = acct_info.xbzrle_cache_miss;
+        }
         s->dirty_pages_rate = num_dirty_pages_period * 1000
             / (end_time - start_time);
         s->dirty_bytes_rate = s->dirty_pages_rate * TARGET_PAGE_SIZE;
diff --git a/hmp.c b/hmp.c
index 77a8d18..18a850d 100644
--- a/hmp.c
+++ b/hmp.c
@@ -214,6 +214,8 @@  void hmp_info_migrate(Monitor *mon, const QDict *qdict)
                        info->xbzrle_cache->pages);
         monitor_printf(mon, "xbzrle cache miss: %" PRIu64 "\n",
                        info->xbzrle_cache->cache_miss);
+        monitor_printf(mon, "xbzrle cache miss rate: %0.2f\n",
+                       info->xbzrle_cache->cache_miss_rate);
         monitor_printf(mon, "xbzrle overflow : %" PRIu64 "\n",
                        info->xbzrle_cache->overflow);
     }
diff --git a/include/migration/migration.h b/include/migration/migration.h
index 9e62b99..430e48d 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -126,6 +126,7 @@  uint64_t xbzrle_mig_bytes_transferred(void);
 uint64_t xbzrle_mig_pages_transferred(void);
 uint64_t xbzrle_mig_pages_overflow(void);
 uint64_t xbzrle_mig_pages_cache_miss(void);
+double xbzrle_mig_cache_miss_rate(void);
 
 void ram_handle_compressed(void *host, uint8_t ch, uint64_t size);
 
diff --git a/migration.c b/migration.c
index e8f8ca5..9477576 100644
--- a/migration.c
+++ b/migration.c
@@ -185,6 +185,7 @@  static void get_xbzrle_cache_stats(MigrationInfo *info)
         info->xbzrle_cache->bytes = xbzrle_mig_bytes_transferred();
         info->xbzrle_cache->pages = xbzrle_mig_pages_transferred();
         info->xbzrle_cache->cache_miss = xbzrle_mig_pages_cache_miss();
+        info->xbzrle_cache->cache_miss_rate = xbzrle_mig_cache_miss_rate();
         info->xbzrle_cache->overflow = xbzrle_mig_pages_overflow();
     }
 }
diff --git a/qapi-schema.json b/qapi-schema.json
index 4592f62..c6f043d 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -674,13 +674,16 @@ 
 #
 # @cache-miss: number of cache miss
 #
+# @cache-miss-rate: rate of cache miss (since 2.1)
+#
 # @overflow: number of overflows
 #
 # Since: 1.2
 ##
 { 'type': 'XBZRLECacheStats',
   'data': {'cache-size': 'int', 'bytes': 'int', 'pages': 'int',
-           'cache-miss': 'int', 'overflow': 'int' } }
+           'cache-miss': 'int', 'cache-miss-rate': 'number',
+           'overflow': 'int' } }
 
 ##
 # @MigrationInfo
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 0820510..3096c31 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -2979,6 +2979,7 @@  The main json-object contains the following:
          - "bytes": number of bytes transferred for XBZRLE compressed pages
          - "pages": number of XBZRLE compressed pages
          - "cache-miss": number of XBRZRLE page cache misses
+         - "cache-miss-rate": rate of XBRZRLE page cache misses
          - "overflow": number of times XBZRLE overflows.  This means
            that the XBZRLE encoding was bigger than just sent the
            whole page, and then we sent the whole page instead (as as
@@ -3087,6 +3088,7 @@  Examples:
             "bytes":20971520,
             "pages":2444343,
             "cache-miss":2244,
+            "cache-miss-rate":0.123,
             "overflow":34434
          }
       }