netdev - Re: [PATCH 2/2] rps: changes to bnx2x to get device hash

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Date:	Wed, 11 Nov 2009 15:21:03 -0800
From:	"Matt Carlson" <mcarlson@...adcom.com>
To:	"Tom Herbert" <therbert@...gle.com>
cc:	"David Miller" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH 2/2] rps: changes to bnx2x to get device hash

On Tue, Nov 10, 2009 at 10:53:36PM -0800, Tom Herbert wrote:
> @@ -6223,9 +6257,10 @@ static int bnx2x_init_common(struct bnx2x *bp)
>  	bnx2x_init_block(bp, PBF_BLOCK, COMMON_STAGE);
> 
>  	REG_WR(bp, SRC_REG_SOFT_RST, 1);
> -	for (i = SRC_REG_KEYRSS0_0; i <= SRC_REG_KEYRSS1_9; i += 4) {
> -		REG_WR(bp, i, 0xc0cac01a);
> -		/* TODO: replace with something meaningful */
> +	{
> +		int i;
> +		for (i = SRC_REG_KEYRSS0_0; i <= SRC_REG_KEYRSS1_9; i += 4)
> +			REG_WR(bp, i, random32());
>  	}
>  	bnx2x_init_block(bp, SRCH_BLOCK, COMMON_STAGE);
>  #ifdef BCM_CNIC

Is a random hash key really better than arbitrary static values?  
Setting the hash key to random values means, from chip reset to chip
reset, you could get different performance results.  Unless we
we understood how the key affects performance, I would think that
reproducable performance numbers would be more desirable, no?

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