netdev - Re: [PATCH net-next] hv_netvsc: Use simple parser for IPv4 and v6 headers

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Date:	Wed, 16 Dec 2015 21:34:22 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Haiyang Zhang <haiyangz@...rosoft.com>, davem@...emloft.net,
	netdev@...r.kernel.org
Cc:	kys@...rosoft.com, olaf@...fle.de, linux-kernel@...r.kernel.org,
	driverdev-devel@...uxdriverproject.org
Subject: Re: [PATCH net-next] hv_netvsc: Use simple parser for IPv4 and v6
 headers

Hello.

On 12/16/2015 09:03 PM, Haiyang Zhang wrote:

> To avoid performance overhead when using skb_flow_dissect_flow_keys(),
> we switch to the simple parsers to get the IP and port numbers.
>
> Performance comparison: throughput (Gbps):
> Number of connections, before patch, after patch
> 1			8.56		10.18
> 4			11.17		14.07
> 16			12.21		21.78
> 64			18.71		32.08
> 256			15.92		26.32
> 1024			8.41		15.49
> 3000			7.82		11.58
>
> Signed-off-by: Haiyang Zhang <haiyangz@...rosoft.com>
> Tested-by: Simon Xiao <sixiao@...rosoft.com>
> Reviewed-by: K. Y. Srinivasan <kys@...rosoft.com>
> ---
>   drivers/net/hyperv/netvsc_drv.c |   38 +++++++++++++++++++++++++++++---------
>   1 files changed, 29 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
> index 1c8db9a..e28951f 100644
> --- a/drivers/net/hyperv/netvsc_drv.c
> +++ b/drivers/net/hyperv/netvsc_drv.c
> @@ -237,20 +237,40 @@ static u32 comp_hash(u8 *key, int klen, void *data, int dlen)
[...]
> +	if (iphdr->version == 4) {
> +		dbuf[0] = iphdr->saddr;
> +		dbuf[1] = iphdr->daddr;
> +		if (iphdr->protocol == IPPROTO_TCP) {
> +			dbuf[2] = *(__be32 *)&tcp_hdr(skb)->source;
> +			data_len = 12;
> +		} else {
> +			data_len = 8;
> +		}
> +	} else if (ipv6hdr->version == 6) {
> +		memcpy(dbuf, &ipv6hdr->saddr, 32);
> +		if (ipv6hdr->nexthdr == IPPROTO_TCP) {
> +			dbuf[8] = *(__be32 *)&tcp_hdr(skb)->source;
> +			data_len = 36;
> +		} else {
> +			data_len = 32;
> +		}
> +	} else {
> +		return false;
> +	}

    This is asking to be a *switch* statement.

[...]

MBR, Sergei

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