Re: [PATCH v4 14/18] migration/rdma: register memory for multifd RDMA channels

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Chuan Zheng (zhengchuan@huawei.com) wrote:
> Signed-off-by: Zhimin Feng <fengzhimin1@huawei.com>
> Signed-off-by: Chuan Zheng <zhengchuan@huawei.com>

This could do with a description in the commit message of the sequence;
I think you're waiting for the semaphore; doing the registratin, then
waiting again to say that everyone has finished???

> ---
>  migration/multifd.c |  3 ++
>  migration/rdma.c    | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 93 insertions(+), 2 deletions(-)
> 
> diff --git a/migration/multifd.c b/migration/multifd.c
> index 919a414..1186246 100644
> --- a/migration/multifd.c
> +++ b/migration/multifd.c
> @@ -537,6 +537,9 @@ void multifd_send_terminate_threads(Error *err)
>          qemu_mutex_lock(&p->mutex);
>          p->quit = true;
>          qemu_sem_post(&p->sem);
> +        if (migrate_use_rdma()) {
> +            qemu_sem_post(&p->sem_sync);
> +        }
>          qemu_mutex_unlock(&p->mutex);
>      }
>  }
> diff --git a/migration/rdma.c b/migration/rdma.c
> index 1095a8f..c906cc7 100644
> --- a/migration/rdma.c
> +++ b/migration/rdma.c
> @@ -3838,6 +3838,19 @@ static int rdma_load_hook(QEMUFile *f, void *opaque, uint64_t flags, void *data)
>          return rdma_block_notification_handle(opaque, data);
>  
>      case RAM_CONTROL_HOOK:
> +        if (migrate_use_multifd()) {
> +            int i;
> +            MultiFDRecvParams *multifd_recv_param = NULL;
> +            int thread_count = migrate_multifd_channels();
> +            /* Inform dest recv_thread to poll */
> +            for (i = 0; i < thread_count; i++) {
> +                if (get_multifd_recv_param(i, &multifd_recv_param)) {
> +                    return -1;
> +                }
> +                qemu_sem_post(&multifd_recv_param->sem_sync);
> +            }
> +        }
> +
>          return qemu_rdma_registration_handle(f, opaque);
>  
>      default:
> @@ -3910,6 +3923,24 @@ static int qemu_rdma_registration_stop(QEMUFile *f, void *opaque,
>          head.type = RDMA_CONTROL_RAM_BLOCKS_REQUEST;
>          trace_qemu_rdma_registration_stop_ram();
>  
> +        if (migrate_use_multifd()) {
> +            /*
> +             * Inform the multifd channels to register memory
> +             */
> +            int i;
> +            int thread_count = migrate_multifd_channels();
> +            MultiFDSendParams *multifd_send_param = NULL;
> +            for (i = 0; i < thread_count; i++) {
> +                ret = get_multifd_send_param(i, &multifd_send_param);
> +                if (ret) {
> +                    error_report("rdma: error getting multifd(%d)", i);
> +                    return ret;
> +                }
> +
> +                qemu_sem_post(&multifd_send_param->sem_sync);
> +            }
> +        }
> +
>          /*
>           * Make sure that we parallelize the pinning on both sides.
>           * For very large guests, doing this serially takes a really
> @@ -3968,6 +3999,21 @@ static int qemu_rdma_registration_stop(QEMUFile *f, void *opaque,
>                      rdma->dest_blocks[i].remote_host_addr;
>              local->block[i].remote_rkey = rdma->dest_blocks[i].remote_rkey;
>          }
> +        /* Wait for all multifd channels to complete registration */
> +        if (migrate_use_multifd()) {
> +            int i;
> +            int thread_count = migrate_multifd_channels();
> +            MultiFDSendParams *multifd_send_param = NULL;
> +            for (i = 0; i < thread_count; i++) {
> +                ret = get_multifd_send_param(i, &multifd_send_param);
> +                if (ret) {
> +                    error_report("rdma: error getting multifd(%d)", i);
> +                    return ret;
> +                }
> +
> +                qemu_sem_wait(&multifd_send_param->sem);
> +            }
> +        }
>      }
>  
>      trace_qemu_rdma_registration_stop(flags);
> @@ -3979,6 +4025,24 @@ static int qemu_rdma_registration_stop(QEMUFile *f, void *opaque,
>          goto err;
>      }
>  
> +    if (migrate_use_multifd()) {
> +        /*
> +         * Inform src send_thread to send FINISHED signal.
> +         * Wait for multifd RDMA send threads to poll the CQE.
> +         */
> +        int i;
> +        int thread_count = migrate_multifd_channels();
> +        MultiFDSendParams *multifd_send_param = NULL;
> +        for (i = 0; i < thread_count; i++) {
> +            ret = get_multifd_send_param(i, &multifd_send_param);
> +            if (ret < 0) {
> +                goto err;
> +            }
> +
> +            qemu_sem_post(&multifd_send_param->sem_sync);
> +        }
> +    }
> +
>      return 0;
>  err:
>      rdma->error_state = ret;
> @@ -4355,19 +4419,37 @@ static void *multifd_rdma_send_thread(void *opaque)
>  {
>      MultiFDSendParams *p = opaque;
>      Error *local_err = NULL;
> +    int ret = 0;
> +    RDMAControlHeader head = { .len = 0, .repeat = 1 };
>  
>      trace_multifd_send_thread_start(p->id);
>      if (multifd_send_initial_packet(p, &local_err) < 0) {
>          goto out;
>      }
>  
> +    /* wait for semaphore notification to register memory */
> +    qemu_sem_wait(&p->sem_sync);
> +    if (qemu_rdma_registration(p->rdma) < 0) {
> +        goto out;
> +    }
> +    /*
> +     * Inform the main RDMA thread to run when multifd
> +     * RDMA thread have completed registration.
> +     */
> +    qemu_sem_post(&p->sem);
>      while (true) {
> +        qemu_sem_wait(&p->sem_sync);
>          WITH_QEMU_LOCK_GUARD(&p->mutex) {
>              if (p->quit) {
>                  break;
>              }
>          }
> -        qemu_sem_wait(&p->sem);

Is this something where you put the line in just a few patches earlier -
if so, put it in the right place in the original patch.

Dave

> +        /* Send FINISHED to the destination */
> +        head.type = RDMA_CONTROL_REGISTER_FINISHED;
> +        ret = qemu_rdma_exchange_send(p->rdma, &head, NULL, NULL, NULL, NULL);
> +        if (ret < 0) {
> +            return NULL;
> +        }
>      }
>  
>  out:
> @@ -4406,14 +4488,20 @@ static void multifd_rdma_send_channel_setup(MultiFDSendParams *p)
>  static void *multifd_rdma_recv_thread(void *opaque)
>  {
>      MultiFDRecvParams *p = opaque;
> +    int ret = 0;
>  
>      while (true) {
> +        qemu_sem_wait(&p->sem_sync);
>          WITH_QEMU_LOCK_GUARD(&p->mutex) {
>              if (p->quit) {
>                  break;
>              }
>          }
> -        qemu_sem_wait(&p->sem_sync);
> +        ret = qemu_rdma_registration_handle(p->file, p->c);
> +        if (ret < 0) {
> +            qemu_file_set_error(p->file, ret);
> +            break;
> +        }
>      }
>  
>      WITH_QEMU_LOCK_GUARD(&p->mutex) {
> -- 
> 1.8.3.1
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK