From: Alex Rosenbaum Date: Tue, 30 Jun 2015 09:28:00 +0000 (+0200) Subject: mlx4: avoid requesting Tx completion events to improve performance X-Git-Tag: spdx-start~8893 X-Git-Url: http://git.droids-corp.org/?a=commitdiff_plain;h=034378216e19ed23df7b0ebc02f4774f04141e4e;p=dpdk.git mlx4: avoid requesting Tx completion events to improve performance Instead of requesting a completion event for each TX burst, request it on a fixed schedule once every MLX4_PMD_TX_PER_COMP_REQ (currently 64) packets to improve performance. Signed-off-by: Alex Rosenbaum Signed-off-by: Adrien Mazarguil --- diff --git a/drivers/net/mlx4/mlx4.c b/drivers/net/mlx4/mlx4.c index 1881f5bca6..f76f415c12 100644 --- a/drivers/net/mlx4/mlx4.c +++ b/drivers/net/mlx4/mlx4.c @@ -243,6 +243,8 @@ struct txq { unsigned int elts_head; /* Current index in (*elts)[]. */ unsigned int elts_tail; /* First element awaiting completion. */ unsigned int elts_comp; /* Number of completion requests. */ + unsigned int elts_comp_cd; /* Countdown for next completion request. */ + unsigned int elts_comp_cd_init; /* Initial value for countdown. */ struct mlx4_txq_stats stats; /* TX queue counters. */ linear_t (*elts_linear)[]; /* Linearized buffers. */ struct ibv_mr *mr_linear; /* Memory Region for linearized buffers. */ @@ -810,6 +812,12 @@ txq_alloc_elts(struct txq *txq, unsigned int elts_n) txq->elts_head = 0; txq->elts_tail = 0; txq->elts_comp = 0; + /* Request send completion every MLX4_PMD_TX_PER_COMP_REQ packets or + * at least 4 times per ring. */ + txq->elts_comp_cd_init = + ((MLX4_PMD_TX_PER_COMP_REQ < (elts_n / 4)) ? + MLX4_PMD_TX_PER_COMP_REQ : (elts_n / 4)); + txq->elts_comp_cd = txq->elts_comp_cd_init; txq->elts_linear = elts_linear; txq->mr_linear = mr_linear; assert(ret == 0); @@ -896,9 +904,9 @@ txq_cleanup(struct txq *txq) * Manage TX completions. * * When sending a burst, mlx4_tx_burst() posts several WRs. - * To improve performance, a completion event is only required for the last of - * them. Doing so discards completion information for other WRs, but this - * information would not be used anyway. + * To improve performance, a completion event is only required once every + * MLX4_PMD_TX_PER_COMP_REQ sends. Doing so discards completion information + * for other WRs, but this information would not be used anyway. * * @param txq * Pointer to TX queue structure. @@ -910,7 +918,7 @@ static int txq_complete(struct txq *txq) { unsigned int elts_comp = txq->elts_comp; - unsigned int elts_tail; + unsigned int elts_tail = txq->elts_tail; const unsigned int elts_n = txq->elts_n; struct ibv_wc wcs[elts_comp]; int wcs_n; @@ -932,17 +940,12 @@ txq_complete(struct txq *txq) elts_comp -= wcs_n; assert(elts_comp <= txq->elts_comp); /* - * Work Completion ID contains the associated element index in - * (*txq->elts)[]. Since WCs are returned in order, we only need to - * look at the last WC to clear older Work Requests. - * * Assume WC status is successful as nothing can be done about it * anyway. */ - elts_tail = WR_ID(wcs[wcs_n - 1].wr_id).id; - /* Consume the last WC. */ - if (++elts_tail >= elts_n) - elts_tail = 0; + elts_tail += wcs_n * txq->elts_comp_cd_init; + if (elts_tail >= elts_n) + elts_tail -= elts_n; txq->elts_tail = elts_tail; txq->elts_comp = elts_comp; return 0; @@ -1062,10 +1065,13 @@ mlx4_tx_burst(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n) unsigned int elts_head = txq->elts_head; const unsigned int elts_tail = txq->elts_tail; const unsigned int elts_n = txq->elts_n; + unsigned int elts_comp_cd = txq->elts_comp_cd; + unsigned int elts_comp = 0; unsigned int i; unsigned int max; int err; + assert(elts_comp_cd != 0); txq_complete(txq); max = (elts_n - (elts_head - elts_tail)); if (max > elts_n) @@ -1243,6 +1249,12 @@ mlx4_tx_burst(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n) else #endif wr->send_flags = 0; + /* Request TX completion. */ + if (unlikely(--elts_comp_cd == 0)) { + elts_comp_cd = txq->elts_comp_cd_init; + ++elts_comp; + wr->send_flags |= IBV_SEND_SIGNALED; + } if (++elts_head >= elts_n) elts_head = 0; #ifdef MLX4_PMD_SOFT_COUNTERS @@ -1259,14 +1271,11 @@ stop: txq->stats.opackets += i; #endif *wr_next = NULL; - /* The last WR is the only one asking for a completion event. */ - containerof(wr_next, mlx4_send_wr_t, next)-> - send_flags |= IBV_SEND_SIGNALED; err = mlx4_post_send(txq->qp, head.next, &bad_wr); if (unlikely(err)) { unsigned int unsent = 0; - /* An error occurred, completion event is lost. Fix counters. */ + /* An error occurred, fix counters. */ while (bad_wr != NULL) { struct txq_elt *elt = containerof(bad_wr, struct txq_elt, wr); @@ -1285,6 +1294,14 @@ stop: txq->stats.obytes -= wr->sg_list[j].length; #endif ++unsent; + if (wr->send_flags & IBV_SEND_SIGNALED) { + assert(elts_comp != 0); + --elts_comp; + } + if (elts_comp_cd == txq->elts_comp_cd_init) + elts_comp_cd = 1; + else + ++elts_comp_cd; #ifndef NDEBUG /* For assert(). */ for (j = 0; ((int)j < wr->num_sge); ++j) { @@ -1310,9 +1327,10 @@ stop: DEBUG("%p: mlx4_post_send() failed, %u unprocessed WRs: %s", (void *)txq, unsent, ((err <= -1) ? "Internal error" : strerror(err))); - } else - ++txq->elts_comp; + } txq->elts_head = elts_head; + txq->elts_comp += elts_comp; + txq->elts_comp_cd = elts_comp_cd; return i; } diff --git a/drivers/net/mlx4/mlx4.h b/drivers/net/mlx4/mlx4.h index 433aa3b7e3..151c34bfa3 100644 --- a/drivers/net/mlx4/mlx4.h +++ b/drivers/net/mlx4/mlx4.h @@ -51,6 +51,9 @@ /* Maximum number of simultaneous VLAN filters supported. See above. */ #define MLX4_MAX_VLAN_IDS 127 +/* Request send completion once in every 64 sends, might be less. */ +#define MLX4_PMD_TX_PER_COMP_REQ 64 + /* Maximum number of Scatter/Gather Elements per Work Request. */ #ifndef MLX4_PMD_SGE_WR_N #define MLX4_PMD_SGE_WR_N 4