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Fix mlx5en(4) driver to properly call m_defrag().

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When the mlx5en(4) driver was converted to using BUSDMA(9) the call to
m_defrag() was moved after the part of the TX routine that strips the
header from the mbuf chain. Before it called m_defrag it first trimmed
off the now-empty mbufs from the start of the chain. This has the side
effect of also removing the head of the chain that has M_PKTHDR set.
m_defrag() will not defrag a chain that does not have M_PKTHDR set,
thus it was effectively never defragging the mbuf chains.

As it turns out, trimming the mbufs in this fashion is unnecessary since
the call to bus_dmamap_load_mbuf_sg doesn't map empty mbufs anyway, so
remove it.

Differential Revision:	https://reviews.freebsd.org/D12050
Submitted by:	mjoras@
MFC after:	1 week
Sponsored by:	Mellanox Technologies
This commit is contained in:
Hans Petter Selasky 2018-03-08 15:53:04 +00:00
parent 1eb09ad434
commit 7d69d339ad
1 changed files with 12 additions and 18 deletions
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30
sys/dev/mlx5/mlx5_en/mlx5_en_tx.c
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@ -311,22 +311,9 @@ mlx5e_sq_xmit(struct mlx5e_sq *sq, struct mbuf **mbp)
}
dseg = ((struct mlx5_wqe_data_seg *)&wqe->ctrl) + ds_cnt;
/* Trim off empty mbufs */
while (mb->m_len == 0) {
mb = m_free(mb);
/* Check if all data has been inlined */
if (mb == NULL)
goto skip_dma;
}
err = bus_dmamap_load_mbuf_sg(sq->dma_tag, sq->mbuf[pi].dma_map,
mb, segs, &nsegs, BUS_DMA_NOWAIT);
if (err == EFBIG) {
/*
* Update *mbp before defrag in case it was trimmed in the
* loop above
*/
*mbp = mb;
/* Update statistics */
sq->stats.defragged++;
/* Too many mbuf fragments */
@ -343,6 +330,17 @@ mlx5e_sq_xmit(struct mlx5e_sq *sq, struct mbuf **mbp)
if (err != 0)
goto tx_drop;
/* Make sure all mbuf data, if any, is written to RAM */
if (nsegs != 0) {
bus_dmamap_sync(sq->dma_tag, sq->mbuf[pi].dma_map,
BUS_DMASYNC_PREWRITE);
} else {
/* All data was inlined, free the mbuf. */
bus_dmamap_unload(sq->dma_tag, sq->mbuf[pi].dma_map);
m_freem(mb);
mb = NULL;
}
for (x = 0; x != nsegs; x++) {
if (segs[x].ds_len == 0)
continue;
@ -351,7 +349,7 @@ mlx5e_sq_xmit(struct mlx5e_sq *sq, struct mbuf **mbp)
dseg->byte_count = cpu_to_be32((uint32_t)segs[x].ds_len);
dseg++;
}
skip_dma:
ds_cnt = (dseg - ((struct mlx5_wqe_data_seg *)&wqe->ctrl));
wqe->ctrl.opmod_idx_opcode = cpu_to_be32((sq->pc << 8) | opcode);
@ -369,10 +367,6 @@ mlx5e_sq_xmit(struct mlx5e_sq *sq, struct mbuf **mbp)
sq->mbuf[pi].num_wqebbs = DIV_ROUND_UP(ds_cnt, MLX5_SEND_WQEBB_NUM_DS);
sq->pc += sq->mbuf[pi].num_wqebbs;
/* Make sure all mbuf data is written to RAM */
if (mb != NULL)
bus_dmamap_sync(sq->dma_tag, sq->mbuf[pi].dma_map, BUS_DMASYNC_PREWRITE);
sq->stats.packets++;
*mbp = NULL; /* safety clear */
return (0);