[PATCH 2/2] migration: expose RAM stats and timing on destination via query-migrate

[Trieu Huynh <vikingtc4@gmail.com>]

From: Trieu Huynh <vikingtc4@gmail.com>

MigrationStats had all-required QAPI fields, so partially populating
info->ram on the destination would force display of source-only metrics
(dirty-sync-count, precopy-bytes, etc.) as misleading zeros.

Make those source-only fields optional with '*' in the QAPI schema.
Update populate_ram_info() to set them via has_* setters so source
output is unchanged.

As per schema's changes, fill_destination_migration_info() can now
populate info->ram for the COMPLETED case with the fields that are
meaningful on the receive side:

  * total, remaining, page-size         (RAM layout)
  * transferred, normal, normal-bytes   (bytes/pages received)
  * duplicate                           (zero pages received)
  * mbps                                (throughput: transferred*8
                                         /time_ms/1000)
  * pages-per-second                    (total pages / duration in
                                         seconds)

Others optional fields (dirty-sync-count, precopy-bytes,
downtime-bytes, postcopy-bytes, multifd-bytes, postcopy-requests,
dirty-sync-missed-zero-copy, dirty-pages-rate) are left unset and
are absent from the destination output.

On dst, {"execute":"query-migrate"}
* As-is:
{
    "return": {
        "status": "completed"
}
* To-be:
{
    "return": {
        "status": "completed",
        "total-time": 94,
        "ram": {
            "total": 554508288,
            "pages-per-second": 1440234,
            "page-size": 4096,
            "remaining": 0,
            "mbps": 97.955404255319152,
            "transferred": 1150976,
            "duplicate": 135101,
            "normal-bytes": 1150976,
            "normal": 281
        }
    }
}

Signed-off-by: Trieu Huynh <vikingtc4@gmail.com>
---
 migration/migration.c | 35 +++++++++++++++++++++++++++++++++++
 qapi/migration.json   | 14 +++++++-------
 2 files changed, 42 insertions(+), 7 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 17c9a8b344..925d29890d 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1063,17 +1063,24 @@ static void populate_ram_info(MigrationInfo *info, MigrationState *s)
     info->ram->normal = qatomic_read(&mig_stats.normal_pages);
     info->ram->normal_bytes = info->ram->normal * page_size;
     info->ram->mbps = s->mbps;
+    info->ram->has_dirty_sync_count = true;
     info->ram->dirty_sync_count =
         qatomic_read(&mig_stats.dirty_sync_count);
+    info->ram->has_dirty_sync_missed_zero_copy = true;
     info->ram->dirty_sync_missed_zero_copy =
         qatomic_read(&mig_stats.dirty_sync_missed_zero_copy);
+    info->ram->has_postcopy_requests = true;
     info->ram->postcopy_requests =
         qatomic_read(&mig_stats.postcopy_requests);
     info->ram->page_size = page_size;
+    info->ram->has_multifd_bytes = true;
     info->ram->multifd_bytes = qatomic_read(&mig_stats.multifd_bytes);
     info->ram->pages_per_second = s->pages_per_second;
+    info->ram->has_precopy_bytes = true;
     info->ram->precopy_bytes = qatomic_read(&mig_stats.precopy_bytes);
+    info->ram->has_downtime_bytes = true;
     info->ram->downtime_bytes = qatomic_read(&mig_stats.downtime_bytes);
+    info->ram->has_postcopy_bytes = true;
     info->ram->postcopy_bytes = qatomic_read(&mig_stats.postcopy_bytes);
 
     if (migrate_xbzrle()) {
@@ -1094,6 +1101,7 @@ static void populate_ram_info(MigrationInfo *info, MigrationState *s)
 
     if (s->state != MIGRATION_STATUS_COMPLETED) {
         info->ram->remaining = ram_bytes_remaining();
+        info->ram->has_dirty_pages_rate = true;
         info->ram->dirty_pages_rate =
            qatomic_read(&mig_stats.dirty_pages_rate);
     }
@@ -1209,6 +1217,33 @@ static void fill_destination_migration_info(MigrationInfo *info)
     case MIGRATION_STATUS_COMPLETED:
         info->has_status = true;
         fill_destination_postcopy_migration_info(info);
+        if (mis->total_time > 0) {
+            info->has_total_time = true;
+            info->total_time = mis->total_time;
+        }
+        {
+            size_t page_size = qemu_target_page_size();
+            uint64_t normal  = mis->received_normal_pages;
+            uint64_t zero    = mis->received_zero_pages;
+            uint64_t xbzrle  = mis->received_xbzrle_pages;
+
+            info->ram = g_malloc0(sizeof(*info->ram));
+            info->ram->total        = ram_bytes_total();
+            info->ram->remaining    = 0;
+            info->ram->normal       = normal + xbzrle;
+            info->ram->normal_bytes = (normal + xbzrle) * page_size;
+            info->ram->duplicate    = zero;
+            info->ram->transferred  = (normal + xbzrle) * page_size;
+            info->ram->page_size    = page_size;
+
+            if (info->has_total_time) {
+                info->ram->mbps = info->ram->transferred * 8.0
+                                  / info->total_time / 1000.0;
+                info->ram->pages_per_second = (normal + xbzrle + zero)
+                                              * 1000.0 / info->total_time;
+            }
+            /* source-only optional omitted from output */
+        }
         break;
     default:
         return;
diff --git a/qapi/migration.json b/qapi/migration.json
index 7134d4ce47..a695d04a22 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -68,13 +68,13 @@
   'data': {'transferred': 'int', 'remaining': 'int', 'total': 'int' ,
            'duplicate': 'int',
            'normal': 'int',
-           'normal-bytes': 'int', 'dirty-pages-rate': 'int',
-           'mbps': 'number', 'dirty-sync-count': 'int',
-           'postcopy-requests': 'int', 'page-size': 'int',
-           'multifd-bytes': 'uint64', 'pages-per-second': 'uint64',
-           'precopy-bytes': 'uint64', 'downtime-bytes': 'uint64',
-           'postcopy-bytes': 'uint64',
-           'dirty-sync-missed-zero-copy': 'uint64' } }
+           'normal-bytes': 'int', '*dirty-pages-rate': 'int',
+           'mbps': 'number', '*dirty-sync-count': 'int',
+           '*postcopy-requests': 'int', 'page-size': 'int',
+           '*multifd-bytes': 'uint64', 'pages-per-second': 'uint64',
+           '*precopy-bytes': 'uint64', '*downtime-bytes': 'uint64',
+           '*postcopy-bytes': 'uint64',
+           '*dirty-sync-missed-zero-copy': 'uint64' } }
 
 ##
 # @XBZRLECacheStats:
-- 
2.43.0