[PATCH v5 1/2] migration: Make dirty_pages_rate atomic

[Juan Quintela <quintela@redhat.com>]

In this case we use qatomic operations instead of Stat64 wrapper
because there is no stat64_set().  Defining the 64 bit wrapper is
trivial. The one without atomics is more interesting.

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>

---

Don't use __nocheck() variants
---
 migration/migration.c | 6 ++++--
 migration/ram.c       | 5 +++--
 migration/ram.h       | 2 +-
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 22e8586623..712f802962 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1005,7 +1005,8 @@ static void populate_ram_info(MigrationInfo *info, MigrationState *s)
 
     if (s->state != MIGRATION_STATUS_COMPLETED) {
         info->ram->remaining = ram_bytes_remaining();
-        info->ram->dirty_pages_rate = ram_counters.dirty_pages_rate;
+        info->ram->dirty_pages_rate =
+           qatomic_read(&ram_counters.dirty_pages_rate);
     }
 }
 
@@ -2751,7 +2752,8 @@ static void migration_update_counters(MigrationState *s,
      * if we haven't sent anything, we don't want to
      * recalculate. 10000 is a small enough number for our purposes
      */
-    if (ram_counters.dirty_pages_rate && transferred > 10000) {
+    if (qatomic_read(&ram_counters.dirty_pages_rate) &&
+        transferred > 10000) {
         s->expected_downtime = ram_counters.remaining / bandwidth;
     }
 
diff --git a/migration/ram.c b/migration/ram.c
index 01356f60a4..7c534a41e0 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1129,8 +1129,9 @@ static void migration_update_rates(RAMState *rs, int64_t end_time)
     double compressed_size;
 
     /* calculate period counters */
-    ram_counters.dirty_pages_rate = rs->num_dirty_pages_period * 1000
-                / (end_time - rs->time_last_bitmap_sync);
+    qatomic_set(&ram_counters.dirty_pages_rate,
+                rs->num_dirty_pages_period * 1000 /
+                (end_time - rs->time_last_bitmap_sync));
 
     if (!page_count) {
         return;
diff --git a/migration/ram.h b/migration/ram.h
index a6e0d70226..3db0a9d65c 100644
--- a/migration/ram.h
+++ b/migration/ram.h
@@ -41,7 +41,7 @@
  * one thread).
  */
 typedef struct {
-    int64_t dirty_pages_rate;
+    aligned_uint64_t dirty_pages_rate;
     Stat64 dirty_sync_count;
     Stat64 dirty_sync_missed_zero_copy;
     Stat64 downtime_bytes;
-- 
2.40.0