>
> When enabled with DPDK OvS relies on mbufs allocated by mempools to
> receive and output data on DPDK ports. Until now, each OvS dp_packet has
> only one mbuf associated, which is allocated with the maximum possible
> size, taking the MTU into account. This approach, however, doesn't allow
> us to increase the allocated size in an mbuf, if needed, since an mbuf
> is allocated and initialised upon mempool creation. Thus, in the current
> implementatin this is dealt with by calling OVS_NOTEACHED() and
> terminating OvS.
>
> To avoid this, and allow the allocated size to be increased, multiple
> mbufs can be linked together, in the multi-segment mbufs approach. Thus,
> dp_packet_resize__() has been modified to handle the DPBUF_DPDK case
> and
> allocate and link new mbufs together as needed.
>
> Signed-off-by: Tiago Lam <[email protected]>
> ---
> lib/dp-packet.c | 84
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 82 insertions(+), 2 deletions(-)
>
> diff --git a/lib/dp-packet.c b/lib/dp-packet.c
> index 7b603c7..6a57c3c 100644
> --- a/lib/dp-packet.c
> +++ b/lib/dp-packet.c
> @@ -238,8 +238,86 @@ dp_packet_resize__(struct dp_packet *b, size_t
> new_headroom, size_t new_tailroom
>
> switch (b->source) {
> case DPBUF_DPDK:
> - OVS_NOT_REACHED();
> + {
> +#ifdef DPDK_NETDEV
Is it possible for the b->source == DPBUF_DPDK and DPDK_NETDEV to not be
defined? If not, the #ifdef can be removed.
> + uint16_t max_data_len, nb_segs;
> + size_t miss_len;
> + size_t head_diff = 0;
> + struct rte_mbuf *mbuf, *fmbuf;
> + struct rte_mempool *mp;
> +
> + if (!netdev_dpdk_is_multi_segment_mbufs_enabled()) {
> + /* XXX: Handle single mbufs case better */
> + return;
> + }
> +
> + /* Calculate missing length in need of allocation */
> + if (new_headroom != dp_packet_headroom(b)) {
> + /* This is a headroom adjustment. Find out how much, if anything
> */
> + head_diff = new_headroom - dp_packet_headroom(b);
> +
> + if (head_diff <= new_tailroom) {
> + miss_len = 0;
> + } else {
> + miss_len = head_diff - new_tailroom;
> + }
> + } else {
> + /* Otherwise this is a tailroom adjustment */
> + miss_len = new_tailroom - dp_packet_tailroom(b);
> + }
> +
> + mbuf = CONST_CAST(struct rte_mbuf *, &b->mbuf);
> + /* All new allocated mbuf's max data len is the same */
> + max_data_len = mbuf->buf_len - mbuf->data_off;
> + /* Calculate # of needed mbufs to accomodate 'miss_len' */
> + nb_segs = miss_len / max_data_len;
> + if (miss_len % max_data_len) {
> + nb_segs += 1;
> + }
> +
> + /* Proceed with the allocation of new mbufs */
> + mp = mbuf->pool;
> + fmbuf = mbuf;
> + mbuf = rte_pktmbuf_lastseg(mbuf);
> +
> + for (int i = 0; i < nb_segs; i++) {
> + /* This takes care of initialising buf_len, data_len and other
> + * fields properly */
> + struct dp_packet *pkt = dpdk_buf_alloc(mp);
> + mbuf->next = CONST_CAST(struct rte_mbuf *, &pkt->mbuf);
> + if (!mbuf->next) {
> + /* XXX: Flag a WARN and return an error as this will likely
> + * result in undefined behaviour */
> + free_dpdk_buf((struct dp_packet *) fmbuf);
> + fmbuf = NULL;
> + break;
> + }
>
> + fmbuf->nb_segs += 1;
> +
> + mbuf = mbuf->next;
> + }
> +
> + /* Deal with headroom. If 'head_diff' calculated above is different
> + * than zero (thus, positive) the 'new_headroom' requested is bigger
> + * than the currently available headroom and thus, now that the
> needed
> + * space and mbufs have been allocated, the data needs to be shift
> + * right.
> + * XXX: Doesn't verify or take into account that new_headroom may
> fall
> + * outside of an mbuf limits */
> + if (head_diff > 0) {
> + new_headroom = dp_packet_headroom(b) + head_diff;
> +
> + dp_packet_shift(b, head_diff);
> + }
> +
> + new_base = dp_packet_base(b);
> +
> + break;
> +#else
> + OVS_NOT_REACHED();
> +#endif
> + }
> case DPBUF_MALLOC:
> if (new_headroom == dp_packet_headroom(b)) {
> new_base = xrealloc(dp_packet_base(b), new_allocated);
> @@ -263,7 +341,9 @@ dp_packet_resize__(struct dp_packet *b, size_t
> new_headroom, size_t new_tailroom
> OVS_NOT_REACHED();
> }
>
> - dp_packet_set_allocated(b, new_allocated);
> + if (b->source != DPBUF_DPDK) {
> + dp_packet_set_allocated(b, new_allocated);
> + }
> dp_packet_set_base(b, new_base);
>
> new_data = (char *) new_base + new_headroom;
> --
> 2.7.4
>
> _______________________________________________
> dev mailing list
> [email protected]
> https://mail.openvswitch.org/mailman/listinfo/ovs-dev
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