On 31/07/15 11:21, Ananyev, Konstantin wrote: > > >> -----Original Message----- >> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Zoltan Kiss >> Sent: Friday, July 31, 2015 11:04 AM >> To: Liang, Cunming; dev at dpdk.org >> Subject: Re: [dpdk-dev] [PATCH v1] ixgbe: remove vector pmd burst size >> restriction >> >> >> >> On 31/07/15 09:17, Cunming Liang wrote: >>> The patch removes the restriction of burst size on a constant 32. >>> >>> On receive side, the burst size floor now aligns to >>> RTE_IXGBE_DESCS_PER_LOOP power of 2. >>> According to this rule, the burst size less than 4 still won't receive >>> anything. >>> (Before this change, the burst size less than 32 can't receive anything.) >>> >>> On transmit side, the max burst size no longer bind with a constant, >>> however it still >>> require to check the cross tx_rs_thresh violation. >>> >>> There's no obvious performance drop found on both recv_pkts_vec >>> and recv_scattered_pkts_vec on burst size 32. >>> >>> Signed-off-by: Cunming Liang <cunming.liang at intel.com> >>> --- >>> drivers/net/ixgbe/ixgbe_rxtx.c | 3 ++- >>> drivers/net/ixgbe/ixgbe_rxtx.h | 4 +--- >>> drivers/net/ixgbe/ixgbe_rxtx_vec.c | 35 >>> ++++++++++++++++------------------- >>> 3 files changed, 19 insertions(+), 23 deletions(-) >>> >>> diff --git a/drivers/net/ixgbe/ixgbe_rxtx.c b/drivers/net/ixgbe/ixgbe_rxtx.c >>> index 3f808b3..dbdb761 100644 >>> --- a/drivers/net/ixgbe/ixgbe_rxtx.c >>> +++ b/drivers/net/ixgbe/ixgbe_rxtx.c >>> @@ -4008,7 +4008,8 @@ ixgbe_set_rx_function(struct rte_eth_dev *dev) >>> */ >>> } else if (adapter->rx_vec_allowed) { >>> PMD_INIT_LOG(DEBUG, "Vector rx enabled, please make sure RX " >>> - "burst size no less than 32."); >>> + "burst size no less than 4 (port=%d).", >>> + dev->data->port_id); >> >> I think it would be better to use RTE_IXGBE_DESCS_PER_LOOP instead of a >> constant 4. >>> >>> dev->rx_pkt_burst = ixgbe_recv_pkts_vec; >>> } else if (adapter->rx_bulk_alloc_allowed) { >>> diff --git a/drivers/net/ixgbe/ixgbe_rxtx.h b/drivers/net/ixgbe/ixgbe_rxtx.h >>> index 113682a..eb931fe 100644 >>> --- a/drivers/net/ixgbe/ixgbe_rxtx.h >>> +++ b/drivers/net/ixgbe/ixgbe_rxtx.h >>> @@ -47,9 +47,7 @@ >>> (uint64_t) ((mb)->buf_physaddr + RTE_PKTMBUF_HEADROOM) >>> >>> #ifdef RTE_IXGBE_INC_VECTOR >>> -#define RTE_IXGBE_VPMD_RX_BURST 32 >>> -#define RTE_IXGBE_VPMD_TX_BURST 32 >>> -#define RTE_IXGBE_RXQ_REARM_THRESH RTE_IXGBE_VPMD_RX_BURST >>> +#define RTE_IXGBE_RXQ_REARM_THRESH 32 >>> #define RTE_IXGBE_TX_MAX_FREE_BUF_SZ 64 >>> #endif >>> >>> diff --git a/drivers/net/ixgbe/ixgbe_rxtx_vec.c >>> b/drivers/net/ixgbe/ixgbe_rxtx_vec.c >>> index 1c16dec..b72f817 100644 >>> --- a/drivers/net/ixgbe/ixgbe_rxtx_vec.c >>> +++ b/drivers/net/ixgbe/ixgbe_rxtx_vec.c >>> @@ -199,13 +199,11 @@ desc_to_olflags_v(__m128i descs[4], struct rte_mbuf >>> **rx_pkts) >>> #endif >>> >>> /* >>> - * vPMD receive routine, now only accept (nb_pkts == >>> RTE_IXGBE_VPMD_RX_BURST) >>> - * in one loop >>> + * vPMD raw receive routine >> I would keep some warning there, like "(if nb_pkts < >> RTE_IXGBE_DESCS_PER_LOOP, won't receive anything)" >> >>> * >>> * Notice: >>> - * - nb_pkts < RTE_IXGBE_VPMD_RX_BURST, just return no packet >>> - * - nb_pkts > RTE_IXGBE_VPMD_RX_BURST, only scan RTE_IXGBE_VPMD_RX_BURST >>> - * numbers of DD bit >>> + * - floor align nb_pkts to a RTE_IXGBE_DESC_PER_LOOP power-of-two >>> + * - 'nb_pkts < 4' causes 0 packet receiving >> Again, RTE_IXGBE_DESCS_PER_LOOP would be better than 4 >> >>> * - don't support ol_flags for rss and csum err >>> */ >>> static inline uint16_t >>> @@ -240,8 +238,7 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq, struct >>> rte_mbuf **rx_pkts, >>> __m128i dd_check, eop_check; >>> #endif /* RTE_NEXT_ABI */ >>> >>> - if (unlikely(nb_pkts < RTE_IXGBE_VPMD_RX_BURST)) >>> - return 0; >>> + nb_pkts = RTE_ALIGN_FLOOR(nb_pkts, RTE_IXGBE_DESCS_PER_LOOP); >>> >>> /* Just the act of getting into the function from the application is >>> * going to cost about 7 cycles */ >>> @@ -310,7 +307,7 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq, struct >>> rte_mbuf **rx_pkts, >>> * D. fill info. from desc to mbuf >>> */ >>> #endif /* RTE_NEXT_ABI */ >>> - for (pos = 0, nb_pkts_recd = 0; pos < RTE_IXGBE_VPMD_RX_BURST; >>> + for (pos = 0, nb_pkts_recd = 0; pos < nb_pkts; >>> pos += RTE_IXGBE_DESCS_PER_LOOP, >>> rxdp += RTE_IXGBE_DESCS_PER_LOOP) { >>> __m128i descs[RTE_IXGBE_DESCS_PER_LOOP]; >>> @@ -450,13 +447,11 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq, struct >>> rte_mbuf **rx_pkts, >>> } >>> >>> /* >>> - * vPMD receive routine, now only accept (nb_pkts == >>> RTE_IXGBE_VPMD_RX_BURST) >>> - * in one loop >>> + * vPMD receive routine >> Same note here as above >> >>> * >>> * Notice: >>> - * - nb_pkts < RTE_IXGBE_VPMD_RX_BURST, just return no packet >>> - * - nb_pkts > RTE_IXGBE_VPMD_RX_BURST, only scan RTE_IXGBE_VPMD_RX_BURST >>> - * numbers of DD bit >>> + * - floor align nb_pkts to a RTE_IXGBE_DESC_PER_LOOP power-of-two >>> + * - 'nb_pkts < 4' causes 0 packet receiving >>> * - don't support ol_flags for rss and csum err >>> */ >>> uint16_t >>> @@ -470,12 +465,11 @@ static inline uint16_t >>> reassemble_packets(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_bufs, >>> uint16_t nb_bufs, uint8_t *split_flags) >>> { >>> - struct rte_mbuf *pkts[RTE_IXGBE_VPMD_RX_BURST]; /*finished pkts*/ >>> + struct rte_mbuf *pkts[nb_bufs]; /*finished pkts*/ >>> struct rte_mbuf *start = rxq->pkt_first_seg; >>> struct rte_mbuf *end = rxq->pkt_last_seg; >>> unsigned pkt_idx, buf_idx; >>> >>> - >>> for (buf_idx = 0, pkt_idx = 0; buf_idx < nb_bufs; buf_idx++) { >>> if (end != NULL) { >>> /* processing a split packet */ >>> @@ -535,14 +529,17 @@ reassemble_packets(struct ixgbe_rx_queue *rxq, struct >>> rte_mbuf **rx_bufs, >>> * >>> * Notice: >>> * - don't support ol_flags for rss and csum err >>> - * - now only accept (nb_pkts == RTE_IXGBE_VPMD_RX_BURST) >>> + * - will floor align nb_pkts to a RTE_IXGBE_DESC_PER_LOOP power-of-two >>> + * - 'nb_pkts < 4' causes 0 packet receiving >>> */ >>> uint16_t >>> ixgbe_recv_scattered_pkts_vec(void *rx_queue, struct rte_mbuf **rx_pkts, >>> uint16_t nb_pkts) >>> { >>> struct ixgbe_rx_queue *rxq = rx_queue; >>> - uint8_t split_flags[RTE_IXGBE_VPMD_RX_BURST] = {0}; >>> + uint8_t split_flags[nb_pkts]; >>> + >>> + memset(split_flags, 0, nb_pkts); >>> >>> /* get some new buffers */ >>> uint16_t nb_bufs = _recv_raw_pkts_vec(rxq, rx_pkts, nb_pkts, >> >> After this _recv_raw_pkts_vec it checks 32 bytes in split_flags (4x8 >> bytes), that can overrun or miss some flags. >> Btw. Bruce just fixed that part in "ixgbe: fix check for split packets" > > Ah yes, missed that when reviewing, that code would be broken if nb_bufs > 32: > > const uint64_t *split_fl64 = (uint64_t *)split_flags; > if (rxq->pkt_first_seg == NULL && > split_fl64[0] == 0 && split_fl64[1] == 0 && > split_fl64[2] == 0 && split_fl64[3] == 0) > return nb_bufs; > > right?
Yes. And if nb_bufs < (32 -RTE_IXGBE_DESCS_PER_LOOP), it would address into memory outside the array. > > Another thing, that I just thought about: > Right now we invoke ixgbe_rxq_rearm() only at the start of > _recv_raw_pkts_vec(). > Before it was ok, as _recv_raw_pkts_vec() would never try to read more then > 32 RXDs. > But what would happen if nb_pkts > rxq->nb_desc and rxq->rxrearm_nb == 0? Yes, that call would deplete the RX ring, the card wouldn't be able to receive more, so the receive function wouldn't be called again to rearm the ring. > I suppose, _recv_raw_pkts_vec() can wrpa around RXD ring and 'receive' same > packet twice? > So we probably better still limit nb_pkts <= 32 at _recv_raw_pkts_vec(). I agree we should limit nb_pkts. To avoid the above problem it would be enough to limit it to (rxq->nb_desc - 1), but I don't know if there is another factor here we should consider. > > Konstantin > >> >> >>> @@ -667,8 +664,8 @@ ixgbe_xmit_pkts_vec(void *tx_queue, struct rte_mbuf >>> **tx_pkts, >>> uint64_t rs = IXGBE_ADVTXD_DCMD_RS|DCMD_DTYP_FLAGS; >>> int i; >>> >>> - if (unlikely(nb_pkts > RTE_IXGBE_VPMD_TX_BURST)) >>> - nb_pkts = RTE_IXGBE_VPMD_TX_BURST; >>> + /* cross rx_thresh boundary is not allowed */ >>> + nb_pkts = RTE_MIN(nb_pkts, txq->tx_rs_thresh); >>> >>> if (txq->nb_tx_free < txq->tx_free_thresh) >>> ixgbe_tx_free_bufs(txq); >>>
