Hi Adrien
> -----Original Message-----
> From: Adrien Mazarguil [mailto:adrien.mazarg...@6wind.com]
> Sent: Monday, October 30, 2017 4:24 PM
> To: Matan Azrad <ma...@mellanox.com>
> Cc: dev@dpdk.org; Ophir Munk <ophi...@mellanox.com>
> Subject: Re: [PATCH v3 5/7] net/mlx4: separate Tx segment cases
>
> On Mon, Oct 30, 2017 at 10:07:27AM +0000, Matan Azrad wrote:
> > Since single segment packets shouldn't use additional memory to save
> > segments byte count we can prevent additional memory unnecessary
> usage
> > in this case; Prevent loop management.
> >
>
> Sorry for asking but I really don't understand the above, can you reformulate
> the problem addressed by this patch?
>
What's about next?
Optimize single segment case by processing it in different code which prevents
checks and calculations relevant only to multi segment case.
> > Call a dedicated function for handling multi segments case.
>
> This sentence is clearer, I'll base my review on what this patch does, not the
> reasons behind it.
>
> > Signed-off-by: Matan Azrad <ma...@mellanox.com>
> > Signed-off-by: Ophir Munk <ophi...@mellanox.com>
> > ---
> > drivers/net/mlx4/mlx4_rxtx.c | 247
> > +++++++++++++++++++++++++++----------------
> > 1 file changed, 158 insertions(+), 89 deletions(-)
> >
> > diff --git a/drivers/net/mlx4/mlx4_rxtx.c
> > b/drivers/net/mlx4/mlx4_rxtx.c index 8ce70d6..8ea8851 100644
> > --- a/drivers/net/mlx4/mlx4_rxtx.c
> > +++ b/drivers/net/mlx4/mlx4_rxtx.c
> > @@ -62,6 +62,9 @@
> > #include "mlx4_rxtx.h"
> > #include "mlx4_utils.h"
> >
> > +#define WQE_ONE_DATA_SEG_SIZE \
> > + (sizeof(struct mlx4_wqe_ctrl_seg) + sizeof(struct
> > +mlx4_wqe_data_seg))
> > +
> > /**
> > * Pointer-value pair structure used in tx_post_send for saving the first
> > * DWORD (32 byte) of a TXBB.
> > @@ -140,22 +143,19 @@ struct pv {
> > * @return
> > * 0 on success, -1 on failure.
> > */
> > -static int
> > -mlx4_txq_complete(struct txq *txq)
> > +static inline int
>
> While likely harmless, I think the addition of this inline keyword is not
> related
> to this patch.
>
Yes, you right, will be fixed in next version.
> > +mlx4_txq_complete(struct txq *txq, const unsigned int elts_n,
> > + struct mlx4_sq *sq)
>
> Looks like an indentation issue, you should align it to the contents of the
> opening "(" to match the coding style of this file.
>
OK.
> > {
> > unsigned int elts_comp = txq->elts_comp;
> > unsigned int elts_tail = txq->elts_tail;
> > - const unsigned int elts_n = txq->elts_n;
> > struct mlx4_cq *cq = &txq->mcq;
> > - struct mlx4_sq *sq = &txq->msq;
> > struct mlx4_cqe *cqe;
> > uint32_t cons_index = cq->cons_index;
> > uint16_t new_index;
> > uint16_t nr_txbbs = 0;
> > int pkts = 0;
> >
> > - if (unlikely(elts_comp == 0))
> > - return 0;
> > /*
> > * Traverse over all CQ entries reported and handle each WQ entry
> > * reported by them.
> > @@ -238,6 +238,122 @@ struct pv {
> > return buf->pool;
> > }
> >
> > +static int handle_multi_segs(struct rte_mbuf *buf,
> > + struct txq *txq,
> > + struct mlx4_wqe_ctrl_seg **pctrl)
>
> How about naming this function in a way that follows the mlx4_something()
> convention?
>
> Here's a suggestion based on how this function remains tied to
> mlx4_tx_burst():
>
> mlx4_tx_burst_seg()
>
Good, thanks!
> > +{
> > + int wqe_real_size;
> > + int nr_txbbs;
> > + struct pv *pv = (struct pv *)txq->bounce_buf;
> > + struct mlx4_sq *sq = &txq->msq;
> > + uint32_t head_idx = sq->head & sq->txbb_cnt_mask;
> > + struct mlx4_wqe_ctrl_seg *ctrl;
> > + struct mlx4_wqe_data_seg *dseg;
> > + uint32_t lkey;
> > + uintptr_t addr;
> > + uint32_t byte_count;
> > + int pv_counter = 0;
> > +
> > + /* Calculate the needed work queue entry size for this packet. */
> > + wqe_real_size = sizeof(struct mlx4_wqe_ctrl_seg) +
> > + buf->nb_segs * sizeof(struct mlx4_wqe_data_seg);
> > + nr_txbbs = MLX4_SIZE_TO_TXBBS(wqe_real_size);
> > + /*
> > + * Check that there is room for this WQE in the send queue and that
> > + * the WQE size is legal.
> > + */
> > + if (((sq->head - sq->tail) + nr_txbbs +
> > + sq->headroom_txbbs) >= sq->txbb_cnt ||
> > + nr_txbbs > MLX4_MAX_WQE_TXBBS) {
> > + return -1;
> > + }
> > +
>
> Extra empty line.
>
> > + /* Get the control and data entries of the WQE. */
> > + ctrl = (struct mlx4_wqe_ctrl_seg *)mlx4_get_send_wqe(sq,
> head_idx);
> > + dseg = (struct mlx4_wqe_data_seg *)((uintptr_t)ctrl +
> > + sizeof(struct mlx4_wqe_ctrl_seg));
> > + *pctrl = ctrl;
> > + /* Fill the data segments with buffer information. */
> > + struct rte_mbuf *sbuf;
>
> I'm usually fine with mixing declarations and code when there's a good
> reason, however in this case there's no point. sbuf could have been defined
> with the rest at the beginning of the function.
>
OK.
> > +
>
> Extra empty line here as well.
>
> > + for (sbuf = buf; sbuf != NULL; sbuf = sbuf->next, dseg++) {
> > + addr = rte_pktmbuf_mtod(sbuf, uintptr_t);
> > + rte_prefetch0((volatile void *)addr);
> > + /* Handle WQE wraparound. */
> > + if (dseg >= (struct mlx4_wqe_data_seg *)sq->eob)
> > + dseg = (struct mlx4_wqe_data_seg *)sq->buf;
> > + dseg->addr = rte_cpu_to_be_64(addr);
> > + /* Memory region key (big endian) for this memory pool. */
> > + lkey = mlx4_txq_mp2mr(txq, mlx4_txq_mb2mp(sbuf));
> > + dseg->lkey = rte_cpu_to_be_32(lkey); #ifndef NDEBUG
> > + /* Calculate the needed work queue entry size for this
> packet */
> > + if (unlikely(dseg->lkey == rte_cpu_to_be_32((uint32_t)-1))) {
> > + /* MR does not exist. */
> > + DEBUG("%p: unable to get MP <-> MR association",
> > + (void *)txq);
> > + /*
> > + * Restamp entry in case of failure.
> > + * Make sure that size is written correctly
> > + * Note that we give ownership to the SW, not the
> HW.
> > + */
> > + wqe_real_size = sizeof(struct mlx4_wqe_ctrl_seg) +
> > + buf->nb_segs * sizeof(struct
> mlx4_wqe_data_seg);
> > + ctrl->fence_size = (wqe_real_size >> 4) & 0x3f;
> > + mlx4_txq_stamp_freed_wqe(sq, head_idx,
> > + (sq->head & sq->txbb_cnt) ? 0 : 1);
> > + return -1;
> > + }
> > +#endif /* NDEBUG */
> > + if (likely(sbuf->data_len)) {
> > + byte_count = rte_cpu_to_be_32(sbuf->data_len);
> > + } else {
> > + /*
> > + * Zero length segment is treated as inline segment
> > + * with zero data.
> > + */
> > + byte_count = RTE_BE32(0x80000000);
> > + }
> > + /*
> > + * If the data segment is not at the beginning of a
> > + * Tx basic block (TXBB) then write the byte count,
> > + * else postpone the writing to just before updating the
> > + * control segment.
> > + */
> > + if ((uintptr_t)dseg & (uintptr_t)(MLX4_TXBB_SIZE - 1)) {
> > + /*
> > + * Need a barrier here before writing the byte_count
> > + * fields to make sure that all the data is visible
> > + * before the byte_count field is set.
> > + * Otherwise, if the segment begins a new cacheline,
> > + * the HCA prefetcher could grab the 64-byte chunk
> and
> > + * get a valid (!= 0xffffffff) byte count but stale
> > + * data, and end up sending the wrong data.
> > + */
> > + rte_io_wmb();
> > + dseg->byte_count = byte_count;
> > + } else {
> > + /*
> > + * This data segment starts at the beginning of a new
> > + * TXBB, so we need to postpone its byte_count
> writing
> > + * for later.
> > + */
> > + pv[pv_counter].dseg = dseg;
> > + pv[pv_counter++].val = byte_count;
> > + }
> > + }
> > + /* Write the first DWORD of each TXBB save earlier. */
> > + if (pv_counter) {
> > + /* Need a barrier here before writing the byte_count. */
> > + rte_io_wmb();
> > + for (--pv_counter; pv_counter >= 0; pv_counter--)
> > + pv[pv_counter].dseg->byte_count =
> pv[pv_counter].val;
> > + }
> > + /* Fill the control parameters for this packet. */
> > + ctrl->fence_size = (wqe_real_size >> 4) & 0x3f;
> > +
>
> Extra empty line.
>
> > + return nr_txbbs;
> > +}
> > /**
> > * DPDK callback for Tx.
> > *
> > @@ -261,10 +377,11 @@ struct pv {
> > unsigned int i;
> > unsigned int max;
> > struct mlx4_sq *sq = &txq->msq;
> > - struct pv *pv = (struct pv *)txq->bounce_buf;
> > + int nr_txbbs;
> >
> > assert(txq->elts_comp_cd != 0);
> > - mlx4_txq_complete(txq);
> > + if (likely(txq->elts_comp != 0))
> > + mlx4_txq_complete(txq, elts_n, sq);
> > max = (elts_n - (elts_head - txq->elts_tail));
> > if (max > elts_n)
> > max -= elts_n;
> > @@ -283,7 +400,6 @@ struct pv {
> > uint32_t owner_opcode = MLX4_OPCODE_SEND;
> > struct mlx4_wqe_ctrl_seg *ctrl;
> > struct mlx4_wqe_data_seg *dseg;
> > - struct rte_mbuf *sbuf;
> > union {
> > uint32_t flags;
> > uint16_t flags16[2];
> > @@ -291,10 +407,6 @@ struct pv {
> > uint32_t head_idx = sq->head & sq->txbb_cnt_mask;
> > uint32_t lkey;
> > uintptr_t addr;
> > - uint32_t byte_count;
> > - int wqe_real_size;
> > - int nr_txbbs;
> > - int pv_counter = 0;
> >
> > /* Clean up old buffer. */
> > if (likely(elt->buf != NULL)) {
> > @@ -313,40 +425,29 @@ struct pv {
> > } while (tmp != NULL);
> > }
> > RTE_MBUF_PREFETCH_TO_FREE(elt_next->buf);
> > -
> > - /*
> > - * Calculate the needed work queue entry size
> > - * for this packet.
> > - */
> > - wqe_real_size = sizeof(struct mlx4_wqe_ctrl_seg) +
> > - buf->nb_segs * sizeof(struct
> mlx4_wqe_data_seg);
> > - nr_txbbs = MLX4_SIZE_TO_TXBBS(wqe_real_size);
> > - /*
> > - * Check that there is room for this WQE in the send
> > - * queue and that the WQE size is legal.
> > - */
> > - if (((sq->head - sq->tail) + nr_txbbs +
> > - sq->headroom_txbbs) >= sq->txbb_cnt ||
> > - nr_txbbs > MLX4_MAX_WQE_TXBBS) {
> > - elt->buf = NULL;
> > - break;
> > - }
> > - /* Get the control and data entries of the WQE. */
> > - ctrl = (struct mlx4_wqe_ctrl_seg *)
> > - mlx4_get_send_wqe(sq, head_idx);
> > - dseg = (struct mlx4_wqe_data_seg *)((uintptr_t)ctrl +
> > - sizeof(struct mlx4_wqe_ctrl_seg));
> > - /* Fill the data segments with buffer information. */
> > - for (sbuf = buf; sbuf != NULL; sbuf = sbuf->next, dseg++) {
> > - addr = rte_pktmbuf_mtod(sbuf, uintptr_t);
> > + if (buf->nb_segs == 1) {
> > + /*
> > + * Check that there is room for this WQE in the send
> > + * queue and that the WQE size is legal
> > + */
> > + if (((sq->head - sq->tail) + 1 + sq->headroom_txbbs)
> >=
> > + sq->txbb_cnt || 1 > MLX4_MAX_WQE_TXBBS) {
> > + elt->buf = NULL;
> > + break;
> > + }
> > + /* Get the control and data entries of the WQE. */
> > + ctrl = (struct mlx4_wqe_ctrl_seg *)
> > + mlx4_get_send_wqe(sq, head_idx);
> > + dseg = (struct mlx4_wqe_data_seg *)((uintptr_t)ctrl
> +
> > + sizeof(struct mlx4_wqe_ctrl_seg));
> > + addr = rte_pktmbuf_mtod(buf, uintptr_t);
> > rte_prefetch0((volatile void *)addr);
> > /* Handle WQE wraparound. */
> > - if (unlikely(dseg >=
> > - (struct mlx4_wqe_data_seg *)sq->eob))
> > + if (dseg >= (struct mlx4_wqe_data_seg *)sq->eob)
>
> Ideally this change should have been on its own in a fix commit.
>
> > dseg = (struct mlx4_wqe_data_seg *)sq-
> >buf;
> > dseg->addr = rte_cpu_to_be_64(addr);
> > /* Memory region key (big endian). */
> > - lkey = mlx4_txq_mp2mr(txq,
> mlx4_txq_mb2mp(sbuf));
> > + lkey = mlx4_txq_mp2mr(txq,
> mlx4_txq_mb2mp(buf));
> > dseg->lkey = rte_cpu_to_be_32(lkey); #ifndef
> NDEBUG
> > if (unlikely(dseg->lkey ==
> > @@ -360,61 +461,28 @@ struct pv {
> > * Note that we give ownership to the SW,
> > * not the HW.
> > */
> > - ctrl->fence_size = (wqe_real_size >> 4) &
> 0x3f;
> > + ctrl->fence_size =
> > + (WQE_ONE_DATA_SEG_SIZE >> 4) &
> 0x3f;
> > mlx4_txq_stamp_freed_wqe(sq, head_idx,
> > (sq->head & sq->txbb_cnt) ? 0 : 1);
> > elt->buf = NULL;
> > break;
> > }
> > #endif /* NDEBUG */
> > - if (likely(sbuf->data_len)) {
> > - byte_count = rte_cpu_to_be_32(sbuf-
> >data_len);
> > - } else {
> > - /*
> > - * Zero length segment is treated as inline
> > - * segment with zero data.
> > - */
> > - byte_count = RTE_BE32(0x80000000);
> > - }
> > - /*
> > - * If the data segment is not at the beginning
> > - * of a Tx basic block (TXBB) then write the
> > - * byte count, else postpone the writing to
> > - * just before updating the control segment.
> > - */
> > - if ((uintptr_t)dseg & (uintptr_t)(MLX4_TXBB_SIZE -
> 1)) {
> > - /*
> > - * Need a barrier here before writing the
> > - * byte_count fields to make sure that all the
> > - * data is visible before the byte_count field
> > - * is set. otherwise, if the segment begins a
> > - * new cacheline, the HCA prefetcher could
> grab
> > - * the 64-byte chunk and get a valid
> > - * (!= 0xffffffff) byte count but stale data,
> > - * and end up sending the wrong data.
> > - */
> > - rte_io_wmb();
> > - dseg->byte_count = byte_count;
> > - } else {
> > - /*
> > - * This data segment starts at the beginning
> of
> > - * a new TXBB, so we need to postpone its
> > - * byte_count writing for later.
> > - */
> > - pv[pv_counter].dseg = dseg;
> > - pv[pv_counter++].val = byte_count;
> > - }
> > - }
> > - /* Write the first DWORD of each TXBB save earlier. */
> > - if (pv_counter) {
> > - /* Need a barrier before writing the byte_count. */
> > + /* Need a barrier here before byte count store. */
> > rte_io_wmb();
> > - for (--pv_counter; pv_counter >= 0; pv_counter--)
> > - pv[pv_counter].dseg->byte_count =
> > - pv[pv_counter].val;
> > + dseg->byte_count = rte_cpu_to_be_32(buf-
> >data_len);
> > +
>
> Extra empty line.
>
> > + /* Fill the control parameters for this packet. */
> > + ctrl->fence_size = (WQE_ONE_DATA_SEG_SIZE >> 4)
> & 0x3f;
> > + nr_txbbs = 1;
> > + } else {
> > + nr_txbbs = handle_multi_segs(buf, txq, &ctrl);
> > + if (nr_txbbs < 0) {
> > + elt->buf = NULL;
> > + break;
> > + }
> > }
> > - /* Fill the control parameters for this packet. */
> > - ctrl->fence_size = (wqe_real_size >> 4) & 0x3f;
> > /*
> > * For raw Ethernet, the SOLICIT flag is used to indicate
> > * that no ICRC should be calculated.
> > @@ -469,6 +537,7 @@ struct pv {
> > ctrl->owner_opcode = rte_cpu_to_be_32(owner_opcode |
> > ((sq->head & sq->txbb_cnt) ?
> > MLX4_BIT_WQE_OWN :
> 0));
> > +
>
> Extra empty line.
>
> > sq->head += nr_txbbs;
> > elt->buf = buf;
> > bytes_sent += buf->pkt_len;
> > --
> > 1.8.3.1
> >
>
> --
> Adrien Mazarguil
> 6WIND
Thanks!
