netdev - RE: [net-next 13/15] ixgbe: clean up ixgbe_atr_compute_perfect_hash

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <063D6719AE5E284EB5DD2968C1650D6D0F6E224D@AcuExch.aculab.com>
Date:	Thu, 20 Mar 2014 09:44:58 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Jeff Kirsher' <jeffrey.t.kirsher@...el.com>,
	"davem@...emloft.net" <davem@...emloft.net>
CC:	Jacob Keller <jacob.e.keller@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"gospo@...hat.com" <gospo@...hat.com>,
	"sassmann@...hat.com" <sassmann@...hat.com>,
	Arun Sharma <asharma@...com>
Subject: RE: [net-next 13/15] ixgbe: clean up
 ixgbe_atr_compute_perfect_hash_82599

From: Jeff Kirsher
> From: Jacob Keller <jacob.e.keller@...el.com>
> 
> Rather than assign several parameters in a row, we should use a for
> loop, which reduces code size.

And probably increases execution time.
Especially for the first two blocks.

...
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_82599.c
> b/drivers/net/ethernet/intel/ixgbe/ixgbe_82599.c
> index bdac7bd..34ab2fc 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_82599.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_82599.c
> @@ -1597,35 +1597,20 @@ void ixgbe_atr_compute_perfect_hash_82599(union ixgbe_atr_input *input,
>  {
> 
>  	u32 hi_hash_dword, lo_hash_dword, flow_vm_vlan;
> -	u32 bucket_hash = 0;
> +	u32 bucket_hash = 0, hi_dword = 0;
> +	int i;
> 
>  	/* Apply masks to input data */
> -	input->dword_stream[0]  &= input_mask->dword_stream[0];
> -	input->dword_stream[1]  &= input_mask->dword_stream[1];
> -	input->dword_stream[2]  &= input_mask->dword_stream[2];
> -	input->dword_stream[3]  &= input_mask->dword_stream[3];
> -	input->dword_stream[4]  &= input_mask->dword_stream[4];
> -	input->dword_stream[5]  &= input_mask->dword_stream[5];
> -	input->dword_stream[6]  &= input_mask->dword_stream[6];
> -	input->dword_stream[7]  &= input_mask->dword_stream[7];
> -	input->dword_stream[8]  &= input_mask->dword_stream[8];
> -	input->dword_stream[9]  &= input_mask->dword_stream[9];
> -	input->dword_stream[10] &= input_mask->dword_stream[10];
> +	for (i = 0; i <= 10; i++)
> +		input->dword_stream[i] &= input_mask->dword_stream[i];
> 
>  	/* record the flow_vm_vlan bits as they are a key part to the hash */
>  	flow_vm_vlan = ntohl(input->dword_stream[0]);
> 
>  	/* generate common hash dword */
> -	hi_hash_dword = ntohl(input->dword_stream[1] ^
> -				    input->dword_stream[2] ^
> -				    input->dword_stream[3] ^
> -				    input->dword_stream[4] ^
> -				    input->dword_stream[5] ^
> -				    input->dword_stream[6] ^
> -				    input->dword_stream[7] ^
> -				    input->dword_stream[8] ^
> -				    input->dword_stream[9] ^
> -				    input->dword_stream[10]);
> +	for (i = 1; i <= 10; i++)
> +		hi_dword ^= input->dword_stream[i];
> +	hi_hash_dword = ntohl(hi_dword);

If has to be worth doing these ^= at the same time as the & with the mask.
Especially if the compiler can't assume that 'input' and 'input_mask'
don't overlap - which forces some strong sequencing on the instructions.

>  	/* low dword is word swapped version of common */
>  	lo_hash_dword = (hi_hash_dword >> 16) | (hi_hash_dword << 16);
> @@ -1644,21 +1629,8 @@ void ixgbe_atr_compute_perfect_hash_82599(union ixgbe_atr_input *input,
>  	lo_hash_dword ^= flow_vm_vlan ^ (flow_vm_vlan << 16);
> 
>  	/* Process remaining 30 bit of the key */
> -	IXGBE_COMPUTE_BKT_HASH_ITERATION(1);
> -	IXGBE_COMPUTE_BKT_HASH_ITERATION(2);
> -	IXGBE_COMPUTE_BKT_HASH_ITERATION(3);
> -	IXGBE_COMPUTE_BKT_HASH_ITERATION(4);
> -	IXGBE_COMPUTE_BKT_HASH_ITERATION(5);
> -	IXGBE_COMPUTE_BKT_HASH_ITERATION(6);
> -	IXGBE_COMPUTE_BKT_HASH_ITERATION(7);
> -	IXGBE_COMPUTE_BKT_HASH_ITERATION(8);
> -	IXGBE_COMPUTE_BKT_HASH_ITERATION(9);
> -	IXGBE_COMPUTE_BKT_HASH_ITERATION(10);
> -	IXGBE_COMPUTE_BKT_HASH_ITERATION(11);
> -	IXGBE_COMPUTE_BKT_HASH_ITERATION(12);
> -	IXGBE_COMPUTE_BKT_HASH_ITERATION(13);
> -	IXGBE_COMPUTE_BKT_HASH_ITERATION(14);
> -	IXGBE_COMPUTE_BKT_HASH_ITERATION(15);
> +	for (i = 1; i <= 15; i++)
> +		IXGBE_COMPUTE_BKT_HASH_ITERATION(i);
> 
>  	/*
>  	 * Limit hash to 13 bits since max bucket count is 8K.
> --

	David



--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html