From 3106c580fb7cf26691c1ce3aba2223f3ae56d846 Mon Sep 17 00:00:00 2001 From: Magnus Karlsson Date: Mon, 16 Nov 2020 12:12:47 +0100 Subject: [PATCH] i40e: Use batched xsk Tx interfaces to increase performance Use the new batched xsk interfaces for the Tx path in the i40e driver to improve performance. On my machine, this yields a throughput increase of 4% for the l2fwd sample app in xdpsock. If we instead just look at the Tx part, this patch set increases throughput with above 20% for Tx. Note that I had to explicitly loop unroll the inner loop to get to this performance level, by using a pragma. It is honored by both clang and gcc and should be ignored by versions that do not support it. Using the -funroll-loops compiler command line switch on the source file resulted in a loop unrolling on a higher level that lead to a performance decrease instead of an increase. Signed-off-by: Magnus Karlsson Signed-off-by: Daniel Borkmann Acked-by: John Fastabend Link: https://lore.kernel.org/bpf/1605525167-14450-6-git-send-email-magnus.karlsson@gmail.com --- drivers/net/ethernet/intel/i40e/i40e_txrx.c | 11 ++ drivers/net/ethernet/intel/i40e/i40e_txrx.h | 1 + drivers/net/ethernet/intel/i40e/i40e_xsk.c | 119 ++++++++++++++------ drivers/net/ethernet/intel/i40e/i40e_xsk.h | 16 +++ 4 files changed, 112 insertions(+), 35 deletions(-) diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c index d43ce13a93c9..c21548c71bb1 100644 --- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c +++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c @@ -676,6 +676,8 @@ void i40e_free_tx_resources(struct i40e_ring *tx_ring) i40e_clean_tx_ring(tx_ring); kfree(tx_ring->tx_bi); tx_ring->tx_bi = NULL; + kfree(tx_ring->xsk_descs); + tx_ring->xsk_descs = NULL; if (tx_ring->desc) { dma_free_coherent(tx_ring->dev, tx_ring->size, @@ -1277,6 +1279,13 @@ int i40e_setup_tx_descriptors(struct i40e_ring *tx_ring) if (!tx_ring->tx_bi) goto err; + if (ring_is_xdp(tx_ring)) { + tx_ring->xsk_descs = kcalloc(I40E_MAX_NUM_DESCRIPTORS, sizeof(*tx_ring->xsk_descs), + GFP_KERNEL); + if (!tx_ring->xsk_descs) + goto err; + } + u64_stats_init(&tx_ring->syncp); /* round up to nearest 4K */ @@ -1300,6 +1309,8 @@ int i40e_setup_tx_descriptors(struct i40e_ring *tx_ring) return 0; err: + kfree(tx_ring->xsk_descs); + tx_ring->xsk_descs = NULL; kfree(tx_ring->tx_bi); tx_ring->tx_bi = NULL; return -ENOMEM; diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.h b/drivers/net/ethernet/intel/i40e/i40e_txrx.h index 2feed920ef8a..5f531b195959 100644 --- a/drivers/net/ethernet/intel/i40e/i40e_txrx.h +++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.h @@ -389,6 +389,7 @@ struct i40e_ring { struct i40e_channel *ch; struct xdp_rxq_info xdp_rxq; struct xsk_buff_pool *xsk_pool; + struct xdp_desc *xsk_descs; /* For storing descriptors in the AF_XDP ZC path */ } ____cacheline_internodealigned_in_smp; static inline bool ring_uses_build_skb(struct i40e_ring *ring) diff --git a/drivers/net/ethernet/intel/i40e/i40e_xsk.c b/drivers/net/ethernet/intel/i40e/i40e_xsk.c index 20d26321b447..4c44f499fd49 100644 --- a/drivers/net/ethernet/intel/i40e/i40e_xsk.c +++ b/drivers/net/ethernet/intel/i40e/i40e_xsk.c @@ -2,6 +2,7 @@ /* Copyright(c) 2018 Intel Corporation. */ #include +#include #include #include @@ -381,6 +382,69 @@ int i40e_clean_rx_irq_zc(struct i40e_ring *rx_ring, int budget) return failure ? budget : (int)total_rx_packets; } +static void i40e_xmit_pkt(struct i40e_ring *xdp_ring, struct xdp_desc *desc, + unsigned int *total_bytes) +{ + struct i40e_tx_desc *tx_desc; + dma_addr_t dma; + + dma = xsk_buff_raw_get_dma(xdp_ring->xsk_pool, desc->addr); + xsk_buff_raw_dma_sync_for_device(xdp_ring->xsk_pool, dma, desc->len); + + tx_desc = I40E_TX_DESC(xdp_ring, xdp_ring->next_to_use++); + tx_desc->buffer_addr = cpu_to_le64(dma); + tx_desc->cmd_type_offset_bsz = build_ctob(I40E_TX_DESC_CMD_ICRC | I40E_TX_DESC_CMD_EOP, + 0, desc->len, 0); + + *total_bytes += desc->len; +} + +static void i40e_xmit_pkt_batch(struct i40e_ring *xdp_ring, struct xdp_desc *desc, + unsigned int *total_bytes) +{ + u16 ntu = xdp_ring->next_to_use; + struct i40e_tx_desc *tx_desc; + dma_addr_t dma; + u32 i; + + loop_unrolled_for(i = 0; i < PKTS_PER_BATCH; i++) { + dma = xsk_buff_raw_get_dma(xdp_ring->xsk_pool, desc[i].addr); + xsk_buff_raw_dma_sync_for_device(xdp_ring->xsk_pool, dma, desc[i].len); + + tx_desc = I40E_TX_DESC(xdp_ring, ntu++); + tx_desc->buffer_addr = cpu_to_le64(dma); + tx_desc->cmd_type_offset_bsz = build_ctob(I40E_TX_DESC_CMD_ICRC | + I40E_TX_DESC_CMD_EOP, + 0, desc[i].len, 0); + + *total_bytes += desc[i].len; + } + + xdp_ring->next_to_use = ntu; +} + +static void i40e_fill_tx_hw_ring(struct i40e_ring *xdp_ring, struct xdp_desc *descs, u32 nb_pkts, + unsigned int *total_bytes) +{ + u32 batched, leftover, i; + + batched = nb_pkts & ~(PKTS_PER_BATCH - 1); + leftover = nb_pkts & (PKTS_PER_BATCH - 1); + for (i = 0; i < batched; i += PKTS_PER_BATCH) + i40e_xmit_pkt_batch(xdp_ring, &descs[i], total_bytes); + for (i = batched; i < batched + leftover; i++) + i40e_xmit_pkt(xdp_ring, &descs[i], total_bytes); +} + +static void i40e_set_rs_bit(struct i40e_ring *xdp_ring) +{ + u16 ntu = xdp_ring->next_to_use ? xdp_ring->next_to_use - 1 : xdp_ring->count - 1; + struct i40e_tx_desc *tx_desc; + + tx_desc = I40E_TX_DESC(xdp_ring, ntu); + tx_desc->cmd_type_offset_bsz |= (I40E_TX_DESC_CMD_RS << I40E_TXD_QW1_CMD_SHIFT); +} + /** * i40e_xmit_zc - Performs zero-copy Tx AF_XDP * @xdp_ring: XDP Tx ring @@ -390,45 +454,30 @@ int i40e_clean_rx_irq_zc(struct i40e_ring *rx_ring, int budget) **/ static bool i40e_xmit_zc(struct i40e_ring *xdp_ring, unsigned int budget) { - unsigned int sent_frames = 0, total_bytes = 0; - struct i40e_tx_desc *tx_desc = NULL; - struct xdp_desc desc; - dma_addr_t dma; - - while (budget-- > 0) { - if (!xsk_tx_peek_desc(xdp_ring->xsk_pool, &desc)) - break; - - dma = xsk_buff_raw_get_dma(xdp_ring->xsk_pool, desc.addr); - xsk_buff_raw_dma_sync_for_device(xdp_ring->xsk_pool, dma, - desc.len); - - tx_desc = I40E_TX_DESC(xdp_ring, xdp_ring->next_to_use); - tx_desc->buffer_addr = cpu_to_le64(dma); - tx_desc->cmd_type_offset_bsz = - build_ctob(I40E_TX_DESC_CMD_ICRC - | I40E_TX_DESC_CMD_EOP, - 0, desc.len, 0); - - sent_frames++; - total_bytes += desc.len; - - xdp_ring->next_to_use++; - if (xdp_ring->next_to_use == xdp_ring->count) - xdp_ring->next_to_use = 0; + struct xdp_desc *descs = xdp_ring->xsk_descs; + u32 nb_pkts, nb_processed = 0; + unsigned int total_bytes = 0; + + nb_pkts = xsk_tx_peek_release_desc_batch(xdp_ring->xsk_pool, descs, budget); + if (!nb_pkts) + return false; + + if (xdp_ring->next_to_use + nb_pkts >= xdp_ring->count) { + nb_processed = xdp_ring->count - xdp_ring->next_to_use; + i40e_fill_tx_hw_ring(xdp_ring, descs, nb_processed, &total_bytes); + xdp_ring->next_to_use = 0; } - if (tx_desc) { - /* Request an interrupt for the last frame and bump tail ptr. */ - tx_desc->cmd_type_offset_bsz |= (I40E_TX_DESC_CMD_RS << - I40E_TXD_QW1_CMD_SHIFT); - i40e_xdp_ring_update_tail(xdp_ring); + i40e_fill_tx_hw_ring(xdp_ring, &descs[nb_processed], nb_pkts - nb_processed, + &total_bytes); - xsk_tx_release(xdp_ring->xsk_pool); - i40e_update_tx_stats(xdp_ring, sent_frames, total_bytes); - } + /* Request an interrupt for the last frame and bump tail ptr. */ + i40e_set_rs_bit(xdp_ring); + i40e_xdp_ring_update_tail(xdp_ring); + + i40e_update_tx_stats(xdp_ring, nb_pkts, total_bytes); - return !!budget; + return true; } /** diff --git a/drivers/net/ethernet/intel/i40e/i40e_xsk.h b/drivers/net/ethernet/intel/i40e/i40e_xsk.h index 7adfd8539247..ea88f4597a07 100644 --- a/drivers/net/ethernet/intel/i40e/i40e_xsk.h +++ b/drivers/net/ethernet/intel/i40e/i40e_xsk.h @@ -4,6 +4,22 @@ #ifndef _I40E_XSK_H_ #define _I40E_XSK_H_ +/* This value should match the pragma in the loop_unrolled_for + * macro. Why 4? It is strictly empirical. It seems to be a good + * compromise between the advantage of having simultaneous outstanding + * reads to the DMA array that can hide each others latency and the + * disadvantage of having a larger code path. + */ +#define PKTS_PER_BATCH 4 + +#ifdef __clang__ +#define loop_unrolled_for _Pragma("clang loop unroll_count(4)") for +#elif __GNUC__ >= 8 +#define loop_unrolled_for _Pragma("GCC unroll 4") for +#else +#define loop_unrolled_for for +#endif + struct i40e_vsi; struct xsk_buff_pool; struct zero_copy_allocator; -- 2.20.1