On Wed, 2015-12-16 at 10:03 -0800, 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@xxxxxxxxxxxxx>
> Tested-by: Simon Xiao <sixiao@xxxxxxxxxxxxx>
> Reviewed-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
> ---
> 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)
>
> static bool netvsc_set_hash(u32 *hash, struct sk_buff *skb)
> {
> - struct flow_keys flow;
> + struct iphdr *iphdr;
> + struct ipv6hdr *ipv6hdr;
> + __be32 dbuf[9];
> int data_len;
>
> - if (!skb_flow_dissect_flow_keys(skb, &flow, 0) ||
> - !(flow.basic.n_proto == htons(ETH_P_IP) ||
> - flow.basic.n_proto == htons(ETH_P_IPV6)))
> + if (eth_hdr(skb)->h_proto != htons(ETH_P_IP) &&
> + eth_hdr(skb)->h_proto != htons(ETH_P_IPV6))
> return false;
>
> - if (flow.basic.ip_proto == IPPROTO_TCP)
> - data_len = 12;
> - else
> - data_len = 8;
> + iphdr = ip_hdr(skb);
> + ipv6hdr = ipv6_hdr(skb);
> +
> + 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;
> + }
>
> - *hash = comp_hash(netvsc_hash_key, HASH_KEYLEN, &flow, data_len);
> + *hash = comp_hash(netvsc_hash_key, HASH_KEYLEN, dbuf, data_len);
>
> return true;
> }
This looks very very wrong to me.
How many times this is called per second, for the 'one flow' case ?
Don't you use TSO in this driver ?
What about encapsulation ?
I suspect you have a quite different issue here.
You simply could use skb_get_hash() since local TCP flows will provide a
l4 skb->hash and you have no further flow dissection to do.
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