Re: [PATCH v4 08/23] multifd: Move iov from pages to params

[Dr. David Alan Gilbert]

* Juan Quintela (quintela@redhat.com) wrote:
> This will allow us to reduce the number of system calls on the next patch.
> 
> Signed-off-by: Juan Quintela <quintela@redhat.com>
> ---
>  migration/multifd.h |  8 ++++++--
>  migration/multifd.c | 34 ++++++++++++++++++++++++----------
>  2 files changed, 30 insertions(+), 12 deletions(-)
> 
> diff --git a/migration/multifd.h b/migration/multifd.h
> index e57adc783b..c3f18af364 100644
> --- a/migration/multifd.h
> +++ b/migration/multifd.h
> @@ -62,8 +62,6 @@ typedef struct {
>      uint64_t packet_num;
>      /* offset of each page */
>      ram_addr_t *offset;
> -    /* pointer to each page */
> -    struct iovec *iov;
>      RAMBlock *block;
>  } MultiFDPages_t;
>  
> @@ -110,6 +108,10 @@ typedef struct {
>      uint64_t num_pages;
>      /* syncs main thread and channels */
>      QemuSemaphore sem_sync;
> +    /* buffers to send */
> +    struct iovec *iov;
> +    /* number of iovs used */
> +    uint32_t iovs_num;
>      /* used for compression methods */
>      void *data;
>  }  MultiFDSendParams;
> @@ -149,6 +151,8 @@ typedef struct {
>      uint64_t num_pages;
>      /* syncs main thread and channels */
>      QemuSemaphore sem_sync;
> +    /* buffers to recv */
> +    struct iovec *iov;

Why is there the asymmetry between send and recv, where the send
has the iovs_num and the recv doesn't?

Dave

>      /* used for de-compression methods */
>      void *data;
>  } MultiFDRecvParams;
> diff --git a/migration/multifd.c b/migration/multifd.c
> index 4d62850258..f75bd3c188 100644
> --- a/migration/multifd.c
> +++ b/migration/multifd.c
> @@ -86,7 +86,16 @@ static void nocomp_send_cleanup(MultiFDSendParams *p, 
> Error **errp)
>   */
>  static int nocomp_send_prepare(MultiFDSendParams *p, Error **errp)
>  {
> -    p->next_packet_size = p->pages->num * qemu_target_page_size();
> +    MultiFDPages_t *pages = p->pages;
> +    size_t page_size = qemu_target_page_size();
> +
> +    for (int i = 0; i < p->pages->num; i++) {
> +        p->iov[p->iovs_num].iov_base = pages->block->host + pages->offset[i];
> +        p->iov[p->iovs_num].iov_len = page_size;
> +        p->iovs_num++;
> +    }
> +
> +    p->next_packet_size = p->pages->num * page_size;
>      p->flags |= MULTIFD_FLAG_NOCOMP;
>      return 0;
>  }
> @@ -104,7 +113,7 @@ static int nocomp_send_prepare(MultiFDSendParams *p, 
> Error **errp)
>   */
>  static int nocomp_send_write(MultiFDSendParams *p, uint32_t used, Error 
> **errp)
>  {
> -    return qio_channel_writev_all(p->c, p->pages->iov, used, errp);
> +    return qio_channel_writev_all(p->c, p->iov, p->iovs_num, errp);
>  }
>  
>  /**
> @@ -146,13 +155,18 @@ static void nocomp_recv_cleanup(MultiFDRecvParams *p)
>  static int nocomp_recv_pages(MultiFDRecvParams *p, Error **errp)
>  {
>      uint32_t flags = p->flags & MULTIFD_FLAG_COMPRESSION_MASK;
> +    size_t page_size = qemu_target_page_size();
>  
>      if (flags != MULTIFD_FLAG_NOCOMP) {
>          error_setg(errp, "multifd %u: flags received %x flags expected %x",
>                     p->id, flags, MULTIFD_FLAG_NOCOMP);
>          return -1;
>      }
> -    return qio_channel_readv_all(p->c, p->pages->iov, p->pages->num, errp);
> +    for (int i = 0; i < p->pages->num; i++) {
> +        p->iov[i].iov_base = p->pages->block->host + p->pages->offset[i];
> +        p->iov[i].iov_len = page_size;
> +    }
> +    return qio_channel_readv_all(p->c, p->iov, p->pages->num, errp);
>  }
>  
>  static MultiFDMethods multifd_nocomp_ops = {
> @@ -242,7 +256,6 @@ static MultiFDPages_t *multifd_pages_init(size_t size)
>      MultiFDPages_t *pages = g_new0(MultiFDPages_t, 1);
>  
>      pages->allocated = size;
> -    pages->iov = g_new0(struct iovec, size);
>      pages->offset = g_new0(ram_addr_t, size);
>  
>      return pages;
> @@ -254,8 +267,6 @@ static void multifd_pages_clear(MultiFDPages_t *pages)
>      pages->allocated = 0;
>      pages->packet_num = 0;
>      pages->block = NULL;
> -    g_free(pages->iov);
> -    pages->iov = NULL;
>      g_free(pages->offset);
>      pages->offset = NULL;
>      g_free(pages);
> @@ -365,8 +376,6 @@ static int multifd_recv_unfill_packet(MultiFDRecvParams 
> *p, Error **errp)
>              return -1;
>          }
>          p->pages->offset[i] = offset;
> -        p->pages->iov[i].iov_base = block->host + offset;
> -        p->pages->iov[i].iov_len = page_size;
>      }
>  
>      return 0;
> @@ -470,8 +479,6 @@ int multifd_queue_page(QEMUFile *f, RAMBlock *block, 
> ram_addr_t offset)
>  
>      if (pages->block == block) {
>          pages->offset[pages->num] = offset;
> -        pages->iov[pages->num].iov_base = block->host + offset;
> -        pages->iov[pages->num].iov_len = qemu_target_page_size();
>          pages->num++;
>  
>          if (pages->num < pages->allocated) {
> @@ -567,6 +574,8 @@ void multifd_save_cleanup(void)
>          p->packet_len = 0;
>          g_free(p->packet);
>          p->packet = NULL;
> +        g_free(p->iov);
> +        p->iov = NULL;
>          multifd_send_state->ops->send_cleanup(p, &local_err);
>          if (local_err) {
>              migrate_set_error(migrate_get_current(), local_err);
> @@ -654,6 +663,7 @@ static void *multifd_send_thread(void *opaque)
>              uint32_t used = p->pages->num;
>              uint64_t packet_num = p->packet_num;
>              uint32_t flags = p->flags;
> +            p->iovs_num = 0;
>  
>              if (used) {
>                  ret = multifd_send_state->ops->send_prepare(p, &local_err);
> @@ -922,6 +932,7 @@ int multifd_save_setup(Error **errp)
>          p->packet->version = cpu_to_be32(MULTIFD_VERSION);
>          p->name = g_strdup_printf("multifdsend_%d", i);
>          p->tls_hostname = g_strdup(s->hostname);
> +        p->iov = g_new0(struct iovec, page_count);
>          socket_send_channel_create(multifd_new_send_channel_async, p);
>      }
>  
> @@ -1021,6 +1032,8 @@ int multifd_load_cleanup(Error **errp)
>          p->packet_len = 0;
>          g_free(p->packet);
>          p->packet = NULL;
> +        g_free(p->iov);
> +        p->iov = NULL;
>          multifd_recv_state->ops->recv_cleanup(p);
>      }
>      qemu_sem_destroy(&multifd_recv_state->sem_sync);
> @@ -1161,6 +1174,7 @@ int multifd_load_setup(Error **errp)
>                        + sizeof(uint64_t) * page_count;
>          p->packet = g_malloc0(p->packet_len);
>          p->name = g_strdup_printf("multifdrecv_%d", i);
> +        p->iov = g_new0(struct iovec, page_count);
>      }
>  
>      for (i = 0; i < thread_count; i++) {
> -- 
> 2.34.1
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK