Re: [Qemu-devel] [RFC PATCH RDMA support v6: 4/7] Introduce two new capabilities

[Michael R. Hines]

On 04/10/2013 08:47 AM, Orit Wasserman wrote:
> On 04/10/2013 07:29 AM, address@hidden wrote:
> > From: "Michael R. Hines" <address@hidden>
> >
> > RDMA performs very slowly with zero-page checking.
> > Without the ability to disable it, RDMA throughput and
> > latency promises and high performance links cannot be
> > fully realized.
> >
> > On the other hand, dynamic page registration support is also
> > included in the RDMA protocol. This second capability also
> > cannot be fully realized without the ability to enable zero
> > page scanning.
> >
> > So, we have two new capabilities which work together:
> >
> > 1. migrate_set_capability check_for_zero on|off (default on)
> This is not a capability but a migration parameter, the command
> should be named migrate_check_for_zero (on|off) and you will need to add a flag
> to MigrationParams (and it should be in a separate patch as Paolo already 
> requested)

I'm happy to convert to using a command, but is this not consistent with
XBZRLE the capability? The XBZRLE capability does not affect the destination
either - but it is implemented as a capability.

Am I misundertanding?

- Michael

> > 2. migrate_set_capability chunk_register_destination on|off (default off)
> This is indeed a capability as it effect both source and destination

Acknowledged.

 void qemu_put_buffer_async(QEMUFile *f, const uint8_t *buf, int size);
+void qemu_file_set_error(QEMUFile *f, int ret);
+
+void qemu_rdma_cleanup(void *opaque);
+int qemu_rdma_close(void *opaque);
+int qemu_rdma_get_fd(void *opaque);
+int qemu_rdma_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size);
+int qemu_rdma_put_buffer(void *opaque, const uint8_t *buf,
+                            int64_t pos, int size);
+bool qemu_file_mode_is_not_valid(const char * mode);
+
+extern const QEMUFileOps rdma_read_ops;
+extern const QEMUFileOps rdma_write_ops;
 
 static inline void qemu_put_ubyte(QEMUFile *f, unsigned int v)
 {
diff --git a/migration.c b/migration.c
index 3b4b467..875cee3 100644
--- a/migration.c
+++ b/migration.c
@@ -66,6 +66,7 @@ MigrationState *migrate_get_current(void)
         .state = MIG_STATE_SETUP,
         .bandwidth_limit = MAX_THROTTLE,
         .xbzrle_cache_size = DEFAULT_MIGRATE_CACHE_SIZE,
+        .enabled_capabilities[MIGRATION_CAPABILITY_CHECK_FOR_ZERO] = true,
     };
 
     return &current_migration;
@@ -77,6 +78,10 @@ void qemu_start_incoming_migration(const char *uri, Error 
**errp)
 
     if (strstart(uri, "tcp:", &p))
         tcp_start_incoming_migration(p, errp);
+#ifdef CONFIG_RDMA
+    else if (strstart(uri, "rdma:", &p))
+        rdma_start_incoming_migration(p, errp);
+#endif
 #if !defined(WIN32)
     else if (strstart(uri, "exec:", &p))
         exec_start_incoming_migration(p, errp);
@@ -120,8 +125,10 @@ void process_incoming_migration(QEMUFile *f)
     Coroutine *co = qemu_coroutine_create(process_incoming_migration_co);
     int fd = qemu_get_fd(f);
 
-    assert(fd != -1);
-    qemu_set_nonblock(fd);
+    if(fd != -2) { /* rdma returns -2 */
+        assert(fd != -1);
+        qemu_set_nonblock(fd);
+    }
     qemu_coroutine_enter(co, f);
 }
 
@@ -405,6 +412,10 @@ void qmp_migrate(const char *uri, bool has_blk, bool blk,
 
     if (strstart(uri, "tcp:", &p)) {
         tcp_start_outgoing_migration(s, p, &local_err);
+#ifdef CONFIG_RDMA
+    } else if (strstart(uri, "rdma:", &p)) {
+        rdma_start_outgoing_migration(s, p, &local_err);
+#endif
 #if !defined(WIN32)
     } else if (strstart(uri, "exec:", &p)) {
         exec_start_outgoing_migration(s, p, &local_err);
@@ -474,6 +485,24 @@ void qmp_migrate_set_downtime(double value, Error **errp)
     max_downtime = (uint64_t)value;
 }
 
+bool migrate_chunk_register_destination(void)
+{
+    MigrationState *s;
+
+    s = migrate_get_current();
+
+    return 
s->enabled_capabilities[MIGRATION_CAPABILITY_CHUNK_REGISTER_DESTINATION];
+}
+
+bool migrate_check_for_zero(void)
+{
+    MigrationState *s;
+
+    s = migrate_get_current();
+
+    return s->enabled_capabilities[MIGRATION_CAPABILITY_CHECK_FOR_ZERO];
+}
+
 int migrate_use_xbzrle(void)
 {
     MigrationState *s;
diff --git a/qapi-schema.json b/qapi-schema.json
index db542f6..7ebcf99 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -602,7 +602,7 @@
 # Since: 1.2
 ##
 { 'enum': 'MigrationCapability',
-  'data': ['xbzrle'] }
+  'data': ['xbzrle', 'check_for_zero', 'chunk_register_destination'] }
 
 ##
 # @MigrationCapabilityStatus