Re: [PATCH v2 10/16] migration: Don't abuse qemu_file transferred for RDMA

["Leonardo Brás" <leobras@redhat.com>]

On Mon, 2023-05-15 at 21:57 +0200, Juan Quintela wrote:
> Just create a variable for it, the same way that multifd does.  This
> way it is safe to use for other thread, etc, etc.
> 
> Signed-off-by: Juan Quintela <quintela@redhat.com>
> ---
>  migration/migration-stats.h |  4 ++++
>  migration/migration-stats.c |  5 +++--
>  migration/rdma.c            | 22 ++++++++++++++++++++--
>  migration/trace-events      |  2 +-
>  4 files changed, 28 insertions(+), 5 deletions(-)
> 
> diff --git a/migration/migration-stats.h b/migration/migration-stats.h
> index 9568b5b473..2e3e894307 100644
> --- a/migration/migration-stats.h
> +++ b/migration/migration-stats.h
> @@ -89,6 +89,10 @@ typedef struct {
>       * Maximum amount of data we can send in a cycle.
>       */
>      Stat64 rate_limit_max;
> +    /*
> +     * Number of bytes sent through RDMA.
> +     */
> +    Stat64 rdma_bytes;
>      /*
>       * How long has the setup stage took.
>       */
> diff --git a/migration/migration-stats.c b/migration/migration-stats.c
> index abf2d38b18..4d8e9f93b7 100644
> --- a/migration/migration-stats.c
> +++ b/migration/migration-stats.c
> @@ -68,8 +68,9 @@ void migration_rate_reset(QEMUFile *f)
>  uint64_t migration_transferred_bytes(QEMUFile *f)
>  {
>      uint64_t multifd = stat64_get(&mig_stats.multifd_bytes);
> +    uint64_t rdma = stat64_get(&mig_stats.rdma_bytes);
>      uint64_t qemu_file = qemu_file_transferred(f);
>  
> -    trace_migration_transferred_bytes(qemu_file, multifd);
> -    return qemu_file + multifd;
> +    trace_migration_transferred_bytes(qemu_file, multifd, rdma);
> +    return qemu_file + multifd + rdma;
>  }
> diff --git a/migration/rdma.c b/migration/rdma.c
> index 2e4dcff1c9..074456f9df 100644
> --- a/migration/rdma.c
> +++ b/migration/rdma.c
> @@ -2122,9 +2122,18 @@ retry:
>                      return -EIO;
>                  }
>  
> +                /*
> +                 * TODO: Here we are sending something, but we are not
> +                 * accounting for anything transferred.  The following is wrong:
> +                 *
> +                 * stat64_add(&mig_stats.rdma_bytes, sge.length);
> +                 *
> +                 * because we are using some kind of compression.  I
> +                 * would think that head.len would be the more similar
> +                 * thing to a correct value.
> +                 */
>                  stat64_add(&mig_stats.zero_pages,
>                             sge.length / qemu_target_page_size());
> -
>                  return 1;
>              }
>  
> @@ -2232,8 +2241,17 @@ retry:
>  
>      set_bit(chunk, block->transit_bitmap);
>      stat64_add(&mig_stats.normal_pages, sge.length / qemu_target_page_size());
> +    /*
> +     * We are adding to transferred the amount of data written, but no
> +     * overhead at all.  I will asume that RDMA is magicaly and don't
> +     * need to transfer (at least) the addresses where it wants to
> +     * write the pages.  Here it looks like it should be something
> +     * like:
> +     *     sizeof(send_wr) + sge.length
> +     * but this being RDMA, who knows.
> +     */
> +    stat64_add(&mig_stats.rdma_bytes, sge.length);
>      ram_transferred_add(sge.length);
> -    qemu_file_credit_transfer(f, sge.length);
>      rdma->total_writes++;
>  
>      return 0;
> diff --git a/migration/trace-events b/migration/trace-events
> index cdaef7a1ea..54ae5653fd 100644
> --- a/migration/trace-events
> +++ b/migration/trace-events
> @@ -187,7 +187,7 @@ process_incoming_migration_co_postcopy_end_main(void) ""
>  postcopy_preempt_enabled(bool value) "%d"
>  
>  # migration-stats
> -migration_transferred_bytes(uint64_t qemu_file, uint64_t multifd) "qemu_file %" PRIu64 " multifd %" PRIu64
> +migration_transferred_bytes(uint64_t qemu_file, uint64_t multifd, uint64_t rdma) "qemu_file %" PRIu64 " multifd %" PRIu64 " RDMA %" PRIu64
>  
>  # channel.c
>  migration_set_incoming_channel(void *ioc, const char *ioctype) "ioc=%p ioctype=%s"


Reviewed-by: Leonardo Bras <leobras@redhat.com>