在 2023/8/30 21:09, Xueming(Steven) Li 写道:
-----Original Message-----
From: lihuisong (C) <lihuis...@huawei.com>
Sent: 8/30/2023 20:42
To: Xueming(Steven) Li <xuemi...@nvidia.com>; Ori Kam <or...@nvidia.com>
Cc: dev@dpdk.org; fengcheng...@huawei.com; Ivan Malov
<ivan.ma...@arknetworks.am>
Subject: Re: [PATCH v2 1/2] ethdev: add new symmetric hash function
在 2023/8/30 16:38, Xueming(Steven) Li 写道:
-----Original Message-----
From: lihuisong (C) <lihuis...@huawei.com>
Sent: 8/30/2023 15:51
To: Xueming(Steven) Li <xuemi...@nvidia.com>; Ori Kam
<or...@nvidia.com>
Cc: dev@dpdk.org; fengcheng...@huawei.com; Ivan Malov
<ivan.ma...@arknetworks.am>
Subject: Re: [PATCH v2 1/2] ethdev: add new symmetric hash function
Hi Xueming,
在 2023/8/27 16:17, Xueming Li 写道:
The new symmetric hash function swap src/dst L3 address and
L4 ports automatically by sorting.
Signed-off-by: Xueming Li <xuemi...@nvidia.com>
---
lib/ethdev/rte_flow.h | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/lib/ethdev/rte_flow.h b/lib/ethdev/rte_flow.h index
2ebb76dbc0..4f4421ca50 100644
--- a/lib/ethdev/rte_flow.h
+++ b/lib/ethdev/rte_flow.h
@@ -3196,6 +3196,13 @@ enum rte_eth_hash_function {
* src or dst address will xor with zero pair.
*/
RTE_ETH_HASH_FUNCTION_SYMMETRIC_TOEPLITZ,
+ /**
+ * Symmetric Toeplitz: L3 and L4 fields are sorted prior to
+ * the hash function.
+ * If src_ip > dst_ip, swap src_ip and dst_ip.
+ * If src_port > dst_port, swap src_port and dst_port.
+ */
If hash result are computed by the order:
"src_ip+dst_ip+src_port+dst_port"
How to obtain the value of every L3 and L4 field obove?
I still cannot understand how to swap and set these values for these fields?
Hash result is computed by order ""src_ip+dst_ip+src_port+dst_port"
Here is a detailed explanation of standard hash and symmetric hash by key:
https://www.ndsl.kaist.edu/~kyoungsoo/papers/TR-symRSS.pdf
If src_ip > dst_ip, swap them, then the input becomes:
"dst_ip+src_ip+src_port+dst_port" // please note src and dst IP are
swapped.
Same for L4 ports.
get it.
What are the advantages of the symmetric toeplitz sort?
Or why swap here?
It's a different symmetric hash calculation, hardware can support either/all of
them.
From calculation perspective, the hash result distribution is better, the
result is more
suitable to be used as hash table key.
I get it now.
but I have a question.
why not is that if src_ip < dst_ip, then swap src_ip and dst_ip?
I guess this is going to have the same effect as you said, right?
The symmetric toeplitz sort is not a standard algorithm, is just to
enhance the hash result distribution.
If what I understand is right,
it is better that the new RSS algorithm should works on the one of them
("src_ip > dst_ip" or "src_ip < dst_ip").
+ RTE_ETH_HASH_FUNCTION_SYMMETRIC_TOEPLITZ_SORT,
RTE_ETH_HASH_FUNCTION_MAX,
};
