[PATCH 06/14] migration: Use atomic ops properly for page accountings

[Peter Xu]

To prepare for thread-safety on page accountings, at least below counters
need to be accessed only atomically, they are:

        ram_counters.transferred
        ram_counters.duplicate
        ram_counters.normal
        ram_counters.postcopy_bytes

There are a lot of other counters but they won't be accessed outside
migration thread, then they're still safe to be accessed without atomic
ops.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 migration/migration.c | 10 +++++-----
 migration/multifd.c   |  2 +-
 migration/ram.c       | 29 +++++++++++++++--------------
 3 files changed, 21 insertions(+), 20 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 07c74a79a2..0eacc0c99b 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1048,13 +1048,13 @@ static void populate_ram_info(MigrationInfo *info, 
MigrationState *s)
 
     info->has_ram = true;
     info->ram = g_malloc0(sizeof(*info->ram));
-    info->ram->transferred = ram_counters.transferred;
+    info->ram->transferred = qatomic_read(&ram_counters.transferred);
     info->ram->total = ram_bytes_total();
-    info->ram->duplicate = ram_counters.duplicate;
+    info->ram->duplicate = qatomic_read(&ram_counters.duplicate);
     /* legacy value.  It is not used anymore */
     info->ram->skipped = 0;
-    info->ram->normal = ram_counters.normal;
-    info->ram->normal_bytes = ram_counters.normal * page_size;
+    info->ram->normal = qatomic_read(&ram_counters.normal);
+    info->ram->normal_bytes = info->ram->normal * page_size;
     info->ram->mbps = s->mbps;
     info->ram->dirty_sync_count = ram_counters.dirty_sync_count;
     info->ram->dirty_sync_missed_zero_copy =
@@ -1065,7 +1065,7 @@ static void populate_ram_info(MigrationInfo *info, 
MigrationState *s)
     info->ram->pages_per_second = s->pages_per_second;
     info->ram->precopy_bytes = ram_counters.precopy_bytes;
     info->ram->downtime_bytes = ram_counters.downtime_bytes;
-    info->ram->postcopy_bytes = ram_counters.postcopy_bytes;
+    info->ram->postcopy_bytes = qatomic_read(&ram_counters.postcopy_bytes);
 
     if (migrate_use_xbzrle()) {
         info->has_xbzrle_cache = true;
diff --git a/migration/multifd.c b/migration/multifd.c
index 586ddc9d65..460326acd4 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -437,7 +437,7 @@ static int multifd_send_pages(QEMUFile *f)
                 + p->packet_len;
     qemu_file_acct_rate_limit(f, transferred);
     ram_counters.multifd_bytes += transferred;
-    ram_counters.transferred += transferred;
+    qatomic_add(&ram_counters.transferred, transferred);
     qemu_mutex_unlock(&p->mutex);
     qemu_sem_post(&p->sem);
 
diff --git a/migration/ram.c b/migration/ram.c
index 6e7de6087a..5bd3d76bf0 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -432,11 +432,11 @@ static void ram_transferred_add(uint64_t bytes)
     if (runstate_is_running()) {
         ram_counters.precopy_bytes += bytes;
     } else if (migration_in_postcopy()) {
-        ram_counters.postcopy_bytes += bytes;
+        qatomic_add(&ram_counters.postcopy_bytes, bytes);
     } else {
         ram_counters.downtime_bytes += bytes;
     }
-    ram_counters.transferred += bytes;
+    qatomic_add(&ram_counters.transferred, bytes);
 }
 
 void dirty_sync_missed_zero_copy(void)
@@ -725,7 +725,7 @@ void mig_throttle_counter_reset(void)
 
     rs->time_last_bitmap_sync = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
     rs->num_dirty_pages_period = 0;
-    rs->bytes_xfer_prev = ram_counters.transferred;
+    rs->bytes_xfer_prev = qatomic_read(&ram_counters.transferred);
 }
 
 /**
@@ -1085,8 +1085,9 @@ uint64_t ram_pagesize_summary(void)
 
 uint64_t ram_get_total_transferred_pages(void)
 {
-    return  ram_counters.normal + ram_counters.duplicate +
-                compression_counters.pages + xbzrle_counters.pages;
+    return  qatomic_read(&ram_counters.normal) +
+        qatomic_read(&ram_counters.duplicate) +
+        compression_counters.pages + xbzrle_counters.pages;
 }
 
 static void migration_update_rates(RAMState *rs, int64_t end_time)
@@ -1145,8 +1146,8 @@ static void migration_trigger_throttle(RAMState *rs)
 {
     MigrationState *s = migrate_get_current();
     uint64_t threshold = s->parameters.throttle_trigger_threshold;
-
-    uint64_t bytes_xfer_period = ram_counters.transferred - 
rs->bytes_xfer_prev;
+    uint64_t bytes_xfer_period =
+        qatomic_read(&ram_counters.transferred) - rs->bytes_xfer_prev;
     uint64_t bytes_dirty_period = rs->num_dirty_pages_period * 
TARGET_PAGE_SIZE;
     uint64_t bytes_dirty_threshold = bytes_xfer_period * threshold / 100;
 
@@ -1285,7 +1286,7 @@ static int save_zero_page(RAMState *rs, RAMBlock *block, 
ram_addr_t offset)
     int len = save_zero_page_to_file(rs, rs->f, block, offset);
 
     if (len) {
-        ram_counters.duplicate++;
+        qatomic_inc(&ram_counters.duplicate);
         ram_transferred_add(len);
         return 1;
     }
@@ -1322,9 +1323,9 @@ static bool control_save_page(RAMState *rs, RAMBlock 
*block, ram_addr_t offset,
     }
 
     if (bytes_xmit > 0) {
-        ram_counters.normal++;
+        qatomic_inc(&ram_counters.normal);
     } else if (bytes_xmit == 0) {
-        ram_counters.duplicate++;
+        qatomic_inc(&ram_counters.duplicate);
     }
 
     return true;
@@ -1354,7 +1355,7 @@ static int save_normal_page(RAMState *rs, RAMBlock 
*block, ram_addr_t offset,
         qemu_put_buffer(rs->f, buf, TARGET_PAGE_SIZE);
     }
     ram_transferred_add(TARGET_PAGE_SIZE);
-    ram_counters.normal++;
+    qatomic_inc(&ram_counters.normal);
     return 1;
 }
 
@@ -1448,7 +1449,7 @@ update_compress_thread_counts(const CompressParam *param, 
int bytes_xmit)
     ram_transferred_add(bytes_xmit);
 
     if (param->zero_page) {
-        ram_counters.duplicate++;
+        qatomic_inc(&ram_counters.duplicate);
         return;
     }
 
@@ -2620,9 +2621,9 @@ void acct_update_position(QEMUFile *f, size_t size, bool 
zero)
     uint64_t pages = size / TARGET_PAGE_SIZE;
 
     if (zero) {
-        ram_counters.duplicate += pages;
+        qatomic_add(&ram_counters.duplicate, pages);
     } else {
-        ram_counters.normal += pages;
+        qatomic_add(&ram_counters.normal, pages);
         ram_transferred_add(size);
         qemu_file_credit_transfer(f, size);
     }
-- 
2.32.0