Re: [dpdk-dev] [PATCH] Add toeplitz hash algorithm

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed,  8 Apr 2015 15:06:13 -0400
Vladimir Medvedkin <medvedkinv@gmail.com> wrote:

> Software implementation of the Toeplitz hash function used by RSS.
> Can be used either for packet distribution on single queue NIC
> or for simulating of RSS computation on specific NIC (for example
> after GRE header decapsulating).
> 
> Signed-off-by: Vladimir Medvedkin <medvedkinv@gmail.com>

> +enum rte_thash_flag {
> +	RTE_THASH_L3 = 0,	//calculate hash tacking into account only l3 header
> +	RTE_THASH_L4		//calculate hash tacking into account l4 + l4 headers
> +};
> +
> +/**
> + * Prepare special converted key to use with rte_softrss_be()
> + * @param orig
> + *   pointer to original RSS key
> + * @param targ
> + *   pointer to target RSS key
> + */
> +
> +static inline void
> +rte_convert_rss_key(uint32_t *orig, uint32_t *targ)
orig should be const

> +{
> +	int i;
> +	for (i = 0; i < 10; i++) {
> +		targ[i] = rte_be_to_cpu_32(orig[i]);
> +	}
> +}

> +static inline uint32_t
> +rte_softrss(uint32_t sip, uint32_t dip, uint16_t sp, uint16_t dp, enum rte_thash_flag flag, uint32_t *rss_key)

rss_key should be const

> +{
> +	uint32_t ret = 0;
> +	int i;
> +	for (i = 0; i < 32; i++) {
blank line after declaration please

> +		if (sip & (1 << (31 - i))) {
> +			ret ^= (rte_cpu_to_be_32(*rss_key) << i)|(uint32_t)((uint64_t)(rte_cpu_to_be_32(*(rss_key + 1))) >> (32 - i));

Long expression > 80 characters.
Repeated multiple times (should be inline)
Extra parens ()
Extension to 64 bits is only to avoid compiler warning?


> +		}
> +	}
> +	rss_key++;
> +	for (i = 0; i < 32; i++) {
> +		if (dip & (1 << (31 - i))) {
> +			ret ^= (rte_cpu_to_be_32(*rss_key) << i)|(uint32_t)((uint64_t)(rte_cpu_to_be_32(*(rss_key + 1))) >> (32 - i));
> +		}
> +	}
> +        if (flag == RTE_THASH_L4) {
> +		rss_key++;
> +		for (i = 0; i < 32; i++) {
> +			if (((sp<<16)|dp) & (1 << (31 - i))) {
> +				ret ^= (rte_cpu_to_be_32(*rss_key) << i)|(uint32_t)((uint64_t)(rte_cpu_to_be_32(*(rss_key + 1))) >> (32 - i));
> +			}
> +		}
> +	}
> +	return ret;
> +}
> +
> +/**
> + * Optimized implementation.
> + * If you want the calculated hash value matches NIC RSS value
> + * you have to use special converted key.
> + * All ip's and ports have to be CPU byte order.
> + * @param sip
> + *   Source ip address.
> + * @param dip
> + *   Destination ip address.
> + * @param sp
> + *   Source TCP|UDP port.
> + * @param dp
> + *   Destination TCP|UDP port.
> + * @param flag
> + *   RTE_THASH_L3:	calculate hash tacking into account only sip and dip
> + *   RTE_THASH_L4:	calculate hash tacking into account sip, dip, sp and dp
> + * @param *rss_key
> + *   Pointer to 40-byte RSS hash key.
> + * @return
> + *   Calculated hash value.
> + */
> +
> +static inline uint32_t
> +rte_softrss_be(uint32_t sip, uint32_t dip, uint16_t sp, uint16_t dp, enum rte_thash_flag flag, uint32_t *rss_key)
> +{

Same problems as previous code.
Also lots of copy paste (see Do Not Repeat Yourself principle).