Recent changes to 'struct flow_keys' (e.g commit d34af823ff40 ("net: Add
VLAN ID to flow_keys")) introduced a performance regression in netvsc
driver. Is problem is, however, not the above mentioned commit but the
fact that netvsc_set_hash() function did some assumptions on the struct
flow_keys data layout and this is wrong. We need to extract the data we
need (src/dst addresses and ports) after the dissect.
The issue could also be solved in a completely different way: as suggested
by Eric instead of our own homegrown netvsc_set_hash() we could use
skb_get_hash() which does more or less the same. Unfortunately, the
testing done by Simon showed that Hyper-V hosts are not happy with our
Jenkins hash, selecting the output queue with the current algorithm based
on Toeplitz hash works significantly better.
Tested-by: Simon Xiao <sixiao@xxxxxxxxxxxxx>
Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
This patch is an alternative to Haiyang's "hv_netvsc: Use simple parser
for IPv4 and v6 headers".
---
drivers/net/hyperv/netvsc_drv.c | 22 +++++++++++++++-------
1 file changed, 15 insertions(+), 7 deletions(-)
diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 409b48e..4dea44e 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -238,18 +238,26 @@ static bool netvsc_set_hash(u32 *hash, struct sk_buff *skb)
{
struct flow_keys flow;
int data_len;
+ u8 data[sizeof(flow.addrs) + sizeof(flow.ports)];
- 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 (!skb_flow_dissect_flow_keys(skb, &flow, 0))
return false;
- if (flow.basic.ip_proto == IPPROTO_TCP)
- data_len = 12;
+ if (flow.basic.n_proto == htons(ETH_P_IP))
+ data_len = sizeof(flow.addrs.v4addrs);
+ else if (flow.basic.n_proto == htons(ETH_P_IPV6))
+ data_len = sizeof(flow.addrs.v6addrs);
else
- data_len = 8;
+ return false;
+
+ memcpy(data, &flow.addrs, data_len);
+
+ if (flow.basic.ip_proto == IPPROTO_TCP) {
+ memcpy(data + data_len, &flow.ports, sizeof(flow.ports));
+ data_len += sizeof(flow.ports);
+ }
- *hash = comp_hash(netvsc_hash_key, HASH_KEYLEN, &flow, data_len);
+ *hash = comp_hash(netvsc_hash_key, HASH_KEYLEN, data, data_len);
return true;
}
--
2.4.3
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