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

[Orit Wasserman <owasserm@redhat.com>]

On 04/10/2013 04:13 PM, Michael R. Hines wrote:
> On 04/10/2013 08:47 AM, Orit Wasserman wrote:
>> On 04/10/2013 07:29 AM, mrhines@linux.vnet.ibm.com wrote:
>>> From: "Michael R. Hines" <mrhines@us.ibm.com>
>>>
>>> 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?
> 

XBZRLE requires the destination QEMU to know how to decode it, if the destination is running 
on older QEMU than it won't be able to do so.

Orit
> - 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
> 
>