RE: [PATCH v5 05/10] Add a function named packet_new_nocopy for COLO.

[Zhang, Chen]

> -----Original Message-----
> From: Rao, Lei <lei.rao@intel.com>
> Sent: Thursday, April 1, 2021 3:47 PM
> To: Zhang, Chen <chen.zhang@intel.com>; lizhijian@cn.fujitsu.com;
> jasowang@redhat.com; quintela@redhat.com; dgilbert@redhat.com;
> pbonzini@redhat.com; lukasstraub2@web.de
> Cc: qemu-devel@nongnu.org; Rao, Lei <lei.rao@intel.com>
> Subject: [PATCH v5 05/10] Add a function named packet_new_nocopy for
> COLO.
> 
> From: "Rao, Lei" <lei.rao@intel.com>
> 
> Use the packet_new_nocopy instead of packet_new in the filter-rewriter
> module. There will be one less memory copy in the processing of each
> network packet.
> 
> Signed-off-by: Lei Rao <lei.rao@intel.com>
> ---
>  net/colo.c            | 23 +++++++++++++++++++++++
>  net/colo.h            |  1 +
>  net/filter-rewriter.c |  3 +--
>  3 files changed, 25 insertions(+), 2 deletions(-)
> 
> diff --git a/net/colo.c b/net/colo.c
> index ef00609..58106a8 100644
> --- a/net/colo.c
> +++ b/net/colo.c
> @@ -174,6 +174,29 @@ Packet *packet_new(const void *data, int size, int
> vnet_hdr_len)
>      return pkt;
>  }
> 
> +/*
> + * packet_new_nocopy will not copy data, so the caller can't release
> + * the data. And it will be released in packet_destroy.
> + */
> +Packet *packet_new_nocopy(void *data, int size, int vnet_hdr_len) {
> +    Packet *pkt = g_slice_new(Packet);

We can use g_slice_new0() to avoid "pkt->xxx = 0" here.
For the original code also need do this work to optimize code.

Thanks
Chen

> +
> +    pkt->data = data;
> +    pkt->size = size;
> +    pkt->creation_ms = qemu_clock_get_ms(QEMU_CLOCK_HOST);
> +    pkt->vnet_hdr_len = vnet_hdr_len;
> +    pkt->tcp_seq = 0;
> +    pkt->tcp_ack = 0;
> +    pkt->seq_end = 0;
> +    pkt->header_size = 0;
> +    pkt->payload_size = 0;
> +    pkt->offset = 0;
> +    pkt->flags = 0;
> +
> +    return pkt;
> +}
> +
>  void packet_destroy(void *opaque, void *user_data)  {
>      Packet *pkt = opaque;
> diff --git a/net/colo.h b/net/colo.h
> index 573ab91..d91cd24 100644
> --- a/net/colo.h
> +++ b/net/colo.h
> @@ -101,6 +101,7 @@ bool connection_has_tracked(GHashTable
> *connection_track_table,
>                              ConnectionKey *key);  void
> connection_hashtable_reset(GHashTable *connection_track_table);  Packet
> *packet_new(const void *data, int size, int vnet_hdr_len);
> +Packet *packet_new_nocopy(void *data, int size, int vnet_hdr_len);
>  void packet_destroy(void *opaque, void *user_data);  void
> packet_destroy_partial(void *opaque, void *user_data);
> 
> diff --git a/net/filter-rewriter.c b/net/filter-rewriter.c index 
> 10fe393..cb3a96c
> 100644
> --- a/net/filter-rewriter.c
> +++ b/net/filter-rewriter.c
> @@ -270,8 +270,7 @@ static ssize_t
> colo_rewriter_receive_iov(NetFilterState *nf,
>          vnet_hdr_len = nf->netdev->vnet_hdr_len;
>      }
> 
> -    pkt = packet_new(buf, size, vnet_hdr_len);
> -    g_free(buf);
> +    pkt = packet_new_nocopy(buf, size, vnet_hdr_len);
> 
>      /*
>       * if we get tcp packet
> --
> 1.8.3.1