[Qemu-devel] [PATCH v6 12/12] migration: create a dedicated thread to release rdma resource

[Lidong Chen]

ibv_dereg_mr wait for a long time for big memory size virtual server.

The test result is:
  10GB  326ms
  20GB  699ms
  30GB  1021ms
  40GB  1387ms
  50GB  1712ms
  60GB  2034ms
  70GB  2457ms
  80GB  2807ms
  90GB  3107ms
  100GB 3474ms
  110GB 3735ms
  120GB 4064ms
  130GB 4567ms
  140GB 4886ms

this will cause the guest os hang for a while when migration finished.
So create a dedicated thread to release rdma resource.

Signed-off-by: Lidong Chen <lidongc...@tencent.com>
---
 migration/migration.c |  6 ++++++
 migration/migration.h |  3 +++
 migration/rdma.c      | 47 +++++++++++++++++++++++++++++++----------------
 3 files changed, 40 insertions(+), 16 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 360ee94..f58fe45 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1499,6 +1499,7 @@ void migrate_init(MigrationState *s)
     s->vm_was_running = false;
     s->iteration_initial_bytes = 0;
     s->threshold_size = 0;
+    s->rdma_cleanup_thread_quit = true;
 }
 
 static GSList *migration_blockers;
@@ -1660,6 +1661,10 @@ static bool migrate_prepare(MigrationState *s, bool blk, 
bool blk_inc,
         return false;
     }
 
+    if (s->rdma_cleanup_thread_quit != true) {
+        return false;
+    }
+
     if (runstate_check(RUN_STATE_INMIGRATE)) {
         error_setg(errp, "Guest is waiting for an incoming migration");
         return false;
@@ -3214,6 +3219,7 @@ static void migration_instance_init(Object *obj)
 
     ms->state = MIGRATION_STATUS_NONE;
     ms->mbps = -1;
+    ms->rdma_cleanup_thread_quit = true;
     qemu_sem_init(&ms->pause_sem, 0);
     qemu_mutex_init(&ms->error_mutex);
 
diff --git a/migration/migration.h b/migration/migration.h
index a50c2de..4d1be08 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -231,6 +231,9 @@ struct MigrationState
      * do not trigger spurious decompression errors.
      */
     bool decompress_error_check;
+
+    /* Set this when rdma resource have released */
+    bool rdma_cleanup_thread_quit;
 };
 
 void migrate_set_state(int *state, int old_state, int new_state);
diff --git a/migration/rdma.c b/migration/rdma.c
index 14cdf82..3d1a4ad 100644
--- a/migration/rdma.c
+++ b/migration/rdma.c
@@ -2995,35 +2995,50 @@ static void 
qio_channel_rdma_set_aio_fd_handler(QIOChannel *ioc,
     }
 }
 
-static int qio_channel_rdma_close(QIOChannel *ioc,
-                                  Error **errp)
+static void *qio_channel_rdma_close_thread(void *arg)
 {
-    QIOChannelRDMA *rioc = QIO_CHANNEL_RDMA(ioc);
-    RDMAContext *rdmain, *rdmaout;
-    trace_qemu_rdma_close();
-
-    rdmain = rioc->rdmain;
-    if (rdmain) {
-        atomic_rcu_set(&rioc->rdmain, NULL);
-    }
+    RDMAContext **rdma = arg;
+    RDMAContext *rdmain = rdma[0];
+    RDMAContext *rdmaout = rdma[1];
+    MigrationState *s = migrate_get_current();
 
-    rdmaout = rioc->rdmaout;
-    if (rdmaout) {
-        atomic_rcu_set(&rioc->rdmaout, NULL);
-    }
+    rcu_register_thread();
 
     synchronize_rcu();
-
     if (rdmain) {
         qemu_rdma_cleanup(rdmain);
     }
-
     if (rdmaout) {
         qemu_rdma_cleanup(rdmaout);
     }
 
     g_free(rdmain);
     g_free(rdmaout);
+    g_free(rdma);
+
+    rcu_unregister_thread();
+    s->rdma_cleanup_thread_quit = true;
+    return NULL;
+}
+
+static int qio_channel_rdma_close(QIOChannel *ioc,
+                                  Error **errp)
+{
+    QemuThread t;
+    QIOChannelRDMA *rioc = QIO_CHANNEL_RDMA(ioc);
+    RDMAContext **rdma = g_new0(RDMAContext*, 2);
+    MigrationState *s = migrate_get_current();
+
+    trace_qemu_rdma_close();
+    if (rioc->rdmain || rioc->rdmaout) {
+        rdma[0] =  rioc->rdmain;
+        rdma[1] =  rioc->rdmaout;
+        atomic_rcu_set(&rioc->rdmain, NULL);
+        atomic_rcu_set(&rioc->rdmaout, NULL);
+        s->rdma_cleanup_thread_quit = false;
+        qemu_thread_create(&t, "rdma cleanup", qio_channel_rdma_close_thread,
+                           rdma, QEMU_THREAD_DETACHED);
+    }
 
     return 0;
 }
-- 
1.8.3.1