From: "Morten Brørup" <mb@smartsharesystems.com>
To: "Bili Dong" <qobilidop@gmail.com>
Cc: <yipeng1.wang@intel.com>, <sameh.gobriel@intel.com>,
<bruce.richardson@intel.com>, <vladimir.medvedkin@intel.com>,
<cristian.dumitrescu@intel.com>, <dev@dpdk.org>
Subject: RE: [PATCH v3] hash: add XOR32 hash function
Date: Thu, 16 Feb 2023 10:49:28 +0100 [thread overview]
Message-ID: <98CBD80474FA8B44BF855DF32C47DC35D87741@smartserver.smartshare.dk> (raw)
In-Reply-To: <CAFnY8dFrq21D332YSpZrb4ThZK62be3_i0oJ710bVqctNXyT+Q@mail.gmail.com>
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Hi Bili,
OK. I’m not familiar with this library, but the other function assumes 8 byte aligned data, so this should be OK too.
And with the required function signature, I now understand why you use endian conversions this way.
Acked-by: Morten Brørup <mb@smartsharesystems.com>
Med venlig hilsen / Kind regards,
-Morten Brørup
From: Bili Dong [mailto:qobilidop@gmail.com]
Sent: Wednesday, 15 February 2023 22.40
To: Morten Brørup
Cc: yipeng1.wang@intel.com; sameh.gobriel@intel.com; bruce.richardson@intel.com; vladimir.medvedkin@intel.com; cristian.dumitrescu@intel.com; dev@dpdk.org
Subject: Re: [PATCH v3] hash: add XOR32 hash function
Hi Morten,
Thanks for your comments!
For endianness conversion, I double-checked my usages. I did use both rte_cpu_to_be_32() and rte_be_to_cpu_32(). I might have missed something but I think I used them (4 occurrences) in a semantically meaningful way. Could you point me to the lines that are confusing?
The hash function signature has to conform to https://elixir.bootlin.com/dpdk/v22.11.1/source/lib/table/rte_swx_hash_func.h#L31, so I don't have the freedom to change the parameter type to rte_be32_t, although personally I agree with you and would prefer to make everything consistently big-endian here.
I'm not sure about the byte alignment assumptions used in hash functions. My implementation basically follows the existing CRC32 hash: https://elixir.bootlin.com/dpdk/v22.11.1/source/lib/hash/rte_hash_crc.h#L168, and I don't see byte alignment handled there. Maybe someone more familiar with lib/hash/ could provide some context on this?
Thanks,
Bili
On Wed, Feb 15, 2023 at 3:39 AM Morten Brørup <mb@smartsharesystems.com> wrote:
> From: Bili Dong [mailto:qobilidop@gmail.com]
> Sent: Wednesday, 15 February 2023 12.07
>
> An XOR32 hash is needed in the Software Switch (SWX) Pipeline for its
> use case in P4. We implement it in this patch so it could be easily
> registered in the pipeline later.
>
> Signed-off-by: Bili Dong <qobilidop@gmail.com>
> ---
[...]
> +#define LEFT8b_MASK rte_cpu_to_be_32(0xff000000)
> +#define LEFT16b_MASK rte_cpu_to_be_32(0xffff0000)
> +
> +/**
> + * Calculate XOR32 hash on user-supplied byte array.
> + *
> + * @param data
> + * Data to perform hash on.
> + * @param data_len
> + * How many bytes to use to calculate hash value.
> + * @param init_val
> + * Value to initialise hash generator.
> + * @return
> + * 32bit calculated hash value.
> + */
> +static inline uint32_t
> +rte_hash_xor(const void *data, uint32_t data_len, uint32_t init_val)
> +{
> + uint32_t i;
> + uintptr_t pd = (uintptr_t) data;
> + init_val = rte_cpu_to_be_32(init_val);
> +
> + for (i = 0; i < data_len / 4; i++) {
> + init_val ^= *(const uint32_t *)pd;
> + pd += 4;
> + }
> +
> + if (data_len & 0x2) {
> + init_val ^= *(const uint32_t *)pd & LEFT16b_MASK;
> + pd += 2;
> + }
> +
> + if (data_len & 0x1)
> + init_val ^= *(const uint32_t *)pd & LEFT8b_MASK;
> +
> + init_val = rte_be_to_cpu_32(init_val);
> + return init_val;
> +}
I think that this function has swapped big endian and CPU endian everywhere. The result is the same, but the code would be much less confusing if using rte_cpu_32_to_be() when converting from CPU endian to big endian, and rte_be_to_cpu_32() when converting the other way.
I also suppose that the return type and the init_val parameter were meant to be rte_be32_t.
Also, please document that the byte array must be 32 bit aligned. Alternatively, implement support for unaligned data. You can find inspiration for handling of unaligned data in the __rte_raw_cksum() function:
https://elixir.bootlin.com/dpdk/v22.11.1/source/lib/net/rte_ip.h#L162
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next prev parent reply other threads:[~2023-02-16 9:49 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-15 10:30 [PATCH] " Bili Dong
2023-02-15 10:54 ` [PATCH v2] " Bili Dong
2023-02-15 11:06 ` [PATCH v3] " Bili Dong
2023-02-15 11:39 ` Morten Brørup
2023-02-15 21:39 ` Bili Dong
2023-02-16 9:49 ` Morten Brørup [this message]
2023-02-20 13:49 ` Thomas Monjalon
2023-02-20 17:21 ` Bili Dong
2023-02-20 17:38 ` Thomas Monjalon
2023-02-20 17:51 ` Bruce Richardson
2023-02-20 17:54 ` Bili Dong
2023-02-20 18:19 ` Dumitrescu, Cristian
2023-02-20 18:50 ` Bili Dong
2023-02-20 20:10 ` Medvedkin, Vladimir
2023-02-20 20:17 ` Bili Dong
2023-02-20 20:19 ` Dumitrescu, Cristian
2023-02-20 20:44 ` Bili Dong
2023-02-20 23:04 ` Stephen Hemminger
2023-02-21 1:38 ` Bili Dong
2023-02-21 16:47 ` [PATCH v4] " Bili Dong
2023-02-21 17:55 ` [PATCH v5] " Bili Dong
2023-02-21 19:37 ` [PATCH v6] " Bili Dong
2023-02-21 21:35 ` Bili Dong
2023-06-12 14:56 ` Thomas Monjalon
2023-06-15 17:14 ` Vladimir Medvedkin
2023-06-16 17:15 ` Bili Dong
2023-06-17 20:34 ` Mattias Rönnblom
2023-06-20 19:12 ` [PATCH v7 1/1] " Bili Dong
2023-06-28 19:19 ` Medvedkin, Vladimir
2023-06-29 17:33 ` [PATCH v8] " Bili Dong
2023-07-06 20:08 ` Stephen Hemminger
2023-07-10 22:01 ` Bili Dong
2023-07-10 21:59 ` [PATCH v9] " Bili Dong
2023-09-29 15:38 ` David Marchand
2023-10-03 16:51 ` Medvedkin, Vladimir
2023-10-06 8:06 ` David Marchand
2023-06-17 20:59 ` [PATCH] " Stephen Hemminger
2023-06-20 19:27 ` Bili Dong
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