linux-kernel - Re: [PATCH v3 net-next 4/5] net: enetc: add LSO support for i.MX95 ENETC PF

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Message-ID: <4vfvfzegrk774qlo5fobie5qcleqxqaogphucpzlwlcnq3llqd@aspdtwwqbobn>
Date: Wed, 13 Nov 2024 16:39:11 +0200
From: Ioana Ciornei <ioana.ciornei@....com>
To: Wei Fang <wei.fang@....com>
Cc: claudiu.manoil@....com, vladimir.oltean@....com, xiaoning.wang@....com, 
	andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	pabeni@...hat.com, frank.li@....com, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, imx@...ts.linux.dev
Subject: Re: [PATCH v3 net-next 4/5] net: enetc: add LSO support for i.MX95
 ENETC PF

On Tue, Nov 12, 2024 at 05:14:46PM +0800, Wei Fang wrote:
> ENETC rev 4.1 supports large send offload (LSO), segmenting large TCP
> and UDP transmit units into multiple Ethernet frames. To support LSO,
> software needs to fill some auxiliary information in Tx BD, such as LSO
> header length, frame length, LSO maximum segment size, etc.
> 
> At 1Gbps link rate, TCP segmentation was tested using iperf3, and the
> CPU performance before and after applying the patch was compared through
> the top command. It can be seen that LSO saves a significant amount of
> CPU cycles compared to software TSO.
> 
> Before applying the patch:
> %Cpu(s):  0.1 us,  4.1 sy,  0.0 ni, 85.7 id,  0.0 wa,  0.5 hi,  9.7 si
> 
> After applying the patch:
> %Cpu(s):  0.1 us,  2.3 sy,  0.0 ni, 94.5 id,  0.0 wa,  0.4 hi,  2.6 si
> 
> Signed-off-by: Wei Fang <wei.fang@....com>
> Reviewed-by: Frank Li <Frank.Li@....com>
> ---
> v2: no changes
> v3: use enetc_skb_is_ipv6() helper fucntion which is added in patch 2
> ---
>  drivers/net/ethernet/freescale/enetc/enetc.c  | 266 +++++++++++++++++-
>  drivers/net/ethernet/freescale/enetc/enetc.h  |  15 +
>  .../net/ethernet/freescale/enetc/enetc4_hw.h  |  22 ++
>  .../net/ethernet/freescale/enetc/enetc_hw.h   |  15 +-
>  .../freescale/enetc/enetc_pf_common.c         |   3 +
>  5 files changed, 311 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c b/drivers/net/ethernet/freescale/enetc/enetc.c
> index 7c6b844c2e96..91428bb99f6d 100644
> --- a/drivers/net/ethernet/freescale/enetc/enetc.c
> +++ b/drivers/net/ethernet/freescale/enetc/enetc.c
> @@ -527,6 +527,233 @@ static void enetc_tso_complete_csum(struct enetc_bdr *tx_ring, struct tso_t *tso
>  	}
>  }
>  
> +static inline int enetc_lso_count_descs(const struct sk_buff *skb)
> +{
> +	/* 4 BDs: 1 BD for LSO header + 1 BD for extended BD + 1 BD
> +	 * for linear area data but not include LSO header, namely
> +	 * skb_headlen(skb) - lso_hdr_len. And 1 BD for gap.
> +	 */
> +	return skb_shinfo(skb)->nr_frags + 4;
> +}

Why not move this static inline herper into the header?

> +
> +static int enetc_lso_get_hdr_len(const struct sk_buff *skb)
> +{
> +	int hdr_len, tlen;
> +
> +	tlen = skb_is_gso_tcp(skb) ? tcp_hdrlen(skb) : sizeof(struct udphdr);
> +	hdr_len = skb_transport_offset(skb) + tlen;
> +
> +	return hdr_len;
> +}
> +
> +static void enetc_lso_start(struct sk_buff *skb, struct enetc_lso_t *lso)
> +{
> +	lso->lso_seg_size = skb_shinfo(skb)->gso_size;
> +	lso->ipv6 = enetc_skb_is_ipv6(skb);
> +	lso->tcp = skb_is_gso_tcp(skb);
> +	lso->l3_hdr_len = skb_network_header_len(skb);
> +	lso->l3_start = skb_network_offset(skb);
> +	lso->hdr_len = enetc_lso_get_hdr_len(skb);
> +	lso->total_len = skb->len - lso->hdr_len;
> +}
> +
> +static void enetc_lso_map_hdr(struct enetc_bdr *tx_ring, struct sk_buff *skb,
> +			      int *i, struct enetc_lso_t *lso)
> +{
> +	union enetc_tx_bd txbd_tmp, *txbd;
> +	struct enetc_tx_swbd *tx_swbd;
> +	u16 frm_len, frm_len_ext;
> +	u8 flags, e_flags = 0;
> +	dma_addr_t addr;
> +	char *hdr;
> +
> +	/* Get the fisrt BD of the LSO BDs chain */

s/fisrt/first/