netdev - Re: large divisor for flow classifier

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Date:	Fri, 15 Oct 2010 19:52:41 -0400
From:	Jonathan Thibault <jonathan@...igue.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Patrick McHardy <kaber@...sh.net>, netdev@...r.kernel.org
Subject: Re: large divisor for flow classifier

Merci beaucoup :),

It at least shows I wasn't just confused about the way it works.  In its planned final form, the rate will be set around 175Mbit.  I don't need perfect distribution so things should be fine as long as hosts cannot easily cheat their way into having more bandwidth merely by creating more flows.

Jonathan

On 15/10/10 04:01 PM, Eric Dumazet wrote:
> Le vendredi 15 octobre 2010 à 14:14 -0400, Jonathan Thibault a écrit :
> 
> SFQ is limited to a 1024 divisor
> 
> You might try following patch :
> 
> (8192 is the smallest power of two greater than 6144)
> 
> sizeof(struct sfq_sched_data) becomes 0x2ccc instead of 0x10cc
> 
> keep in mind hash distribution is not perfect.
> 
> What would be the real rate ?
> 
> 
> diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c
> index 3cf478d..c4a53d6 100644
> --- a/net/sched/sch_sfq.c
> +++ b/net/sched/sch_sfq.c
> @@ -77,7 +77,7 @@
>  	It is easy to increase these values, but not in flight.  */
>  
>  #define SFQ_DEPTH		128
> -#define SFQ_HASH_DIVISOR	1024
> +#define SFQ_HASH_DIVISOR	8192
>  
>  /* This type should contain at least SFQ_DEPTH*2 values */
>  typedef unsigned char sfq_index;
> 
> 
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