Re: [PATCH v5 2/7] migration/multifd: put IOV initialization into compression method

[Fabiano Rosas <farosas@suse.de>]

Yuan Liu <yuan1.liu@intel.com> writes:

> Different compression methods may require different numbers of IOVs.
> Based on streaming compression of zlib and zstd, all pages will be
> compressed to a data block, so two IOVs are needed for packet header
> and compressed data block.
>
> Signed-off-by: Yuan Liu <yuan1.liu@intel.com>
> Reviewed-by: Nanhai Zou <nanhai.zou@intel.com>
> ---
>  migration/multifd-zlib.c | 4 ++++
>  migration/multifd-zstd.c | 6 +++++-
>  migration/multifd.c      | 8 +++++---
>  3 files changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/migration/multifd-zlib.c b/migration/multifd-zlib.c
> index 99821cd4d5..8095ef8e28 100644
> --- a/migration/multifd-zlib.c
> +++ b/migration/multifd-zlib.c
> @@ -70,6 +70,10 @@ static int zlib_send_setup(MultiFDSendParams *p, Error **errp)
>          goto err_free_zbuff;
>      }
>      p->compress_data = z;
> +
> +    assert(p->iov == NULL);
> +    /* For packet header and zlib streaming compression block */
> +    p->iov = g_new0(struct iovec, 2);
>      return 0;
>  
>  err_free_zbuff:
> diff --git a/migration/multifd-zstd.c b/migration/multifd-zstd.c
> index 02112255ad..9c9217794e 100644
> --- a/migration/multifd-zstd.c
> +++ b/migration/multifd-zstd.c
> @@ -52,7 +52,6 @@ static int zstd_send_setup(MultiFDSendParams *p, Error **errp)
>      struct zstd_data *z = g_new0(struct zstd_data, 1);
>      int res;
>  
> -    p->compress_data = z;
>      z->zcs = ZSTD_createCStream();
>      if (!z->zcs) {
>          g_free(z);
> @@ -77,6 +76,11 @@ static int zstd_send_setup(MultiFDSendParams *p, Error **errp)
>          error_setg(errp, "multifd %u: out of memory for zbuff", p->id);
>          return -1;
>      }
> +    p->compress_data = z;
> +
> +    assert(p->iov == NULL);
> +    /* For packet header and zstd streaming compression block */
> +    p->iov = g_new0(struct iovec, 2);
>      return 0;
>  }
>  
> diff --git a/migration/multifd.c b/migration/multifd.c
> index 0179422f6d..5155e02ae3 100644
> --- a/migration/multifd.c
> +++ b/migration/multifd.c
> @@ -1181,9 +1181,11 @@ bool multifd_send_setup(void)
>              p->packet = g_malloc0(p->packet_len);
>              p->packet->magic = cpu_to_be32(MULTIFD_MAGIC);
>              p->packet->version = cpu_to_be32(MULTIFD_VERSION);
> -
> -            /* We need one extra place for the packet header */
> -            p->iov = g_new0(struct iovec, page_count + 1);
> +            /* IOVs are initialized in send_setup of compression method */
> +            if (!migrate_multifd_compression()) {
> +                /* We need one extra place for the packet header */
> +                p->iov = g_new0(struct iovec, page_count + 1);
> +            }

This^ should go into nocomp_send_setup:

static int nocomp_send_setup(MultiFDSendParams *p, Error **errp)
{
    if (migrate_zero_copy_send()) {
        p->write_flags |= QIO_CHANNEL_WRITE_FLAG_ZERO_COPY;
    }

    if (multifd_use_packets()) {
        /* We need one extra place for the packet header */
        p->iov = g_new0(struct iovec, p->page_count + 1);
    } else {
        p->iov = g_new0(struct iovec, p->page_count);
    }

    return 0;
}

>          } else {
>              p->iov = g_new0(struct iovec, page_count);
>          }