netdev - Re: [PATCH] Proportional Rate Reduction for TCP.

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Date:	Sat, 13 Aug 2011 22:05:25 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	Nandita Dukkipati <nanditad@...gle.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Tom Herbert <therbert@...gle.com>,
	Yuchung Cheng <ycheng@...gle.com>,
	Matt Mathis <mattmathis@...gle.com>
Subject: Re: [PATCH] Proportional Rate Reduction for TCP.

Nandita Dukkipati <nanditad@...gle.com> writes:
> +
> +	if (tcp_packets_in_flight(tp) > tp->snd_ssthresh) {
> +		if (WARN_ON(!tp->prr_cwnd))
> +			tp->prr_cwnd = 1;
> +		sndcnt = DIV_ROUND_UP(tp->prr_delivered * tp->snd_ssthresh,
> +				      tp->prr_cwnd) - tp->prr_out;
> +	} else {
> +		sndcnt = min_t(int, delta,
> +			       max_t(int, tp->prr_delivered -
> tp->prr_out,

u32s here? This will likely do bad things with large enough windows.

The rest looks good to me as code, but I don't claim to fully understand the 
algorithm. Perhaps a sysctl to turn it off and a linux mib counter when 
it triggers would be useful in addition.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only
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