On 05/07/2018 09:59, Eelco Chaudron wrote: > > > On 4 Jul 2018, at 20:06, Tiago Lam wrote: > >> When a dp_packet is from a DPDK source, and it contains multi-segment >> mbufs, the data_len is not equal to the packet size, pkt_len. Instead, >> the data_len of each mbuf in the chain should be considered while >> distributing the new (provided) size. >> >> To account for the above dp_packet_set_size() has been changed so >> that, >> in the multi-segment mbufs case, only the data_len on the last mbuf of >> the chain and the total size of the packet, pkt_len, are changed. The >> data_len on the intermediate mbufs preceeding the last mbuf is not >> changed by dp_packet_set_size(). Furthermore, in some cases >> dp_packet_set_size() may be used to set a smaller size than the >> current >> packet size, thus effectively trimming the end of the packet. In the >> multi-segment mbufs case this may lead to lingering mbufs that may >> need >> freeing. >> >> __dp_packet_set_data() now also updates an mbufs' data_len after >> setting >> the data offset. This is so that both fields are always in sync for >> each >> mbuf in a chain. >> >> Co-authored-by: Michael Qiu <[email protected]> >> Co-authored-by: Mark Kavanagh <[email protected]> >> Co-authored-by: Przemyslaw Lal <[email protected]> >> Co-authored-by: Marcin Ksiadz <[email protected]> >> Co-authored-by: Yuanhan Liu <[email protected]> >> >> Signed-off-by: Michael Qiu <[email protected]> >> Signed-off-by: Mark Kavanagh <[email protected]> >> Signed-off-by: Przemyslaw Lal <[email protected]> >> Signed-off-by: Marcin Ksiadz <[email protected]> >> Signed-off-by: Yuanhan Liu <[email protected]> >> Signed-off-by: Tiago Lam <[email protected]> >> --- >> lib/dp-packet.h | 76 >> ++++++++++++++++++++++++++++++++++++++++++++++++--------- >> 1 file changed, 64 insertions(+), 12 deletions(-) >> >> diff --git a/lib/dp-packet.h b/lib/dp-packet.h >> index c612ad4..fcbaf60 100644 >> --- a/lib/dp-packet.h >> +++ b/lib/dp-packet.h >> @@ -429,17 +429,49 @@ dp_packet_size(const struct dp_packet *b) >> static inline void >> dp_packet_set_size(struct dp_packet *b, uint32_t v) >> { >> - /* netdev-dpdk does not currently support segmentation; >> consequently, for >> - * all intents and purposes, 'data_len' (16 bit) and 'pkt_len' >> (32 bit) may >> - * be used interchangably. >> - * >> - * On the datapath, it is expected that the size of packets >> - * (and thus 'v') will always be <= UINT16_MAX; this means that >> there is no >> - * loss of accuracy in assigning 'v' to 'data_len'. >> - */ >> - b->mbuf.data_len = (uint16_t)v; /* Current seg length. */ >> - b->mbuf.pkt_len = v; /* Total length of all segments >> linked to >> - * this segment. */ >> + if (b->source == DPBUF_DPDK) { >> + struct rte_mbuf *mbuf = &b->mbuf; >> + uint16_t new_len = v; >> + uint16_t data_len; >> + uint16_t nb_segs = 0; >> + uint16_t pkt_len = 0; >> + >> + /* Trim 'v' length bytes from the end of the chained buffers, >> freeing >> + any buffers that may be left floating */ >> + while (mbuf) { >> + data_len = MIN(new_len, mbuf->data_len); >> + mbuf->data_len = data_len; >> + >> + if (new_len - data_len <= 0) { >> + /* Free the rest of chained mbufs */ >> + free_dpdk_buf(CONTAINER_OF(mbuf->next, struct >> dp_packet, >> + mbuf)); >> + mbuf->next = NULL; >> + } else if (!mbuf->next) { >> + /* Don't assign more than what we have available */ >> + mbuf->data_len = MIN(new_len, >> + mbuf->buf_len - mbuf->data_off); >> + } >> + >> + new_len -= data_len; >> + nb_segs += 1; >> + pkt_len += mbuf->data_len; >> + mbuf = mbuf->next; >> + } >> + >> + /* pkt_len != v would effectively mean that pkt_len < than >> 'v' (as >> + * being bigger is logically impossible). Being < than 'v' >> would mean >> + * the 'v' provided was bigger than the available room, which >> is the >> + * responsibility of the caller to make sure there is enough >> room */ >> + ovs_assert(pkt_len == v); >> + >> + b->mbuf.nb_segs = nb_segs; >> + b->mbuf.pkt_len = pkt_len; >> + } else { >> + b->mbuf.data_len = v; >> + /* Total length of all segments linked to this segment. */ >> + b->mbuf.pkt_len = v; >> + } >> } >> >> static inline uint16_t >> @@ -451,7 +483,27 @@ __packet_data(const struct dp_packet *b) >> static inline void >> __packet_set_data(struct dp_packet *b, uint16_t v) >> { >> - b->mbuf.data_off = v; >> + if (b->source == DPBUF_DPDK) { >> + /* Moving data_off away from the first mbuf in the chain is >> not a >> + * possibility using DPBUF_DPDK dp_packets */ >> + ovs_assert(v == UINT16_MAX || v <= b->mbuf.buf_len - >> b->mbuf.data_off); > > Are you ok this check is ok? Should it not just be “.. || v<= > b->mbuf.buf_len”? > Assuming you have a 1K buffer, data_off is currently 520, now you want > to set the offset to 530? > > 530 <= 1024 - 520 —> ASSERT! >
You're right, this won't assert correctly. I somehow forgot that 'v' is already passed as an offset to the base address, and not a value to be incremented to `data_off`, hence why I was checking on the available tailroom. I'll prepare v3 and run some more tests with it before sending here. Thanks, Tiago. _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
