net: hns3: support dma_map_sg() for multi frags skb

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Using the queue based tx buffer, it is also possible to allocate a
sgl buffer, and use skb_to_sgvec() to convert the skb to the sgvec
in order to support the dma_map_sg() to decreases the overhead of
IOMMU mapping and unmapping.

Firstly, it reduces the number of buffers. For example, a tcp skb
may have a 66-byte header and 3 fragments of 4328, 32768, and 28064
bytes. With this patch, dma_map_sg() will combine them into two
buffers, 66-bytes header and one 65160-bytes fragment by using IOMMU.

Secondly, it reduces the number of dma mapping and unmapping. All the
original 4 buffers are mapped only once rather than 4 times.

The throughput improves above 10% when running single thread of iperf
using TCP when IOMMU is in strict mode.

Suggested-by: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

...

This commit is contained in:

Yunsheng Lin 2021-06-16 14:36:15 +08:00 • committed by David S. Miller

parent 1a00197b7d

commit 7459775e9f

3 changed files with 113 additions and 5 deletions

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111

drivers/net/ethernet/hisilicon/hns3/hns3_enet.c

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4

drivers/net/ethernet/hisilicon/hns3/hns3_enet.h

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3

drivers/net/ethernet/hisilicon/hns3/hns3_ethtool.c

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