migration: Don't abuse qemu_file transferred for RDMA

Just create a variable for it, the same way that multifd does.  This
way it is safe to use for other thread, etc, etc.

Reviewed-by: Leonardo Bras <leobras@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-Id: <20230515195709.63843-11-quintela@redhat.com>

migration/migration-stats.c

@@ -61,8 +61,9 @@ void migration_rate_reset(QEMUFile *f)
 uint64_t migration_transferred_bytes(QEMUFile *f)
 {
     uint64_t multifd = stat64_get(&mig_stats.multifd_bytes);
+    uint64_t rdma = stat64_get(&mig_stats.rdma_bytes);
     uint64_t qemu_file = qemu_file_transferred(f);
 
-    trace_migration_transferred_bytes(qemu_file, multifd);
-    return qemu_file + multifd;
+    trace_migration_transferred_bytes(qemu_file, multifd, rdma);
+    return qemu_file + multifd + rdma;
 }

migration/migration-stats.h

@@ -89,6 +89,10 @@ typedef struct {
      * Maximum amount of data we can send in a cycle.
      */
     Stat64 rate_limit_max;
+    /*
+     * Number of bytes sent through RDMA.
+     */
+    Stat64 rdma_bytes;
     /*
      * Total number of bytes transferred.
      */

migration/rdma.c

@@ -2122,9 +2122,18 @@ static int qemu_rdma_write_one(QEMUFile *f, RDMAContext *rdma,
                     return -EIO;
                 }
 
+                /*
+                 * TODO: Here we are sending something, but we are not
+                 * accounting for anything transferred.  The following is wrong:
+                 *
+                 * stat64_add(&mig_stats.rdma_bytes, sge.length);
+                 *
+                 * because we are using some kind of compression.  I
+                 * would think that head.len would be the more similar
+                 * thing to a correct value.
+                 */
                 stat64_add(&mig_stats.zero_pages,
                            sge.length / qemu_target_page_size());
-
                 return 1;
             }
 
@@ -2232,8 +2241,17 @@ static int qemu_rdma_write_one(QEMUFile *f, RDMAContext *rdma,
 
     set_bit(chunk, block->transit_bitmap);
     stat64_add(&mig_stats.normal_pages, sge.length / qemu_target_page_size());
+    /*
+     * We are adding to transferred the amount of data written, but no
+     * overhead at all.  I will asume that RDMA is magicaly and don't
+     * need to transfer (at least) the addresses where it wants to
+     * write the pages.  Here it looks like it should be something
+     * like:
+     *     sizeof(send_wr) + sge.length
+     * but this being RDMA, who knows.
+     */
+    stat64_add(&mig_stats.rdma_bytes, sge.length);
     ram_transferred_add(sge.length);
-    qemu_file_credit_transfer(f, sge.length);
     rdma->total_writes++;
 
     return 0;

migration/trace-events

@@ -187,7 +187,7 @@ process_incoming_migration_co_postcopy_end_main(void) ""
 postcopy_preempt_enabled(bool value) "%d"
 
 # migration-stats
-migration_transferred_bytes(uint64_t qemu_file, uint64_t multifd) "qemu_file %" PRIu64 " multifd %" PRIu64
+migration_transferred_bytes(uint64_t qemu_file, uint64_t multifd, uint64_t rdma) "qemu_file %" PRIu64 " multifd %" PRIu64 " RDMA %" PRIu64
 
 # channel.c
 migration_set_incoming_channel(void *ioc, const char *ioctype) "ioc=%p ioctype=%s"