netdev - Re: [PATCH v2] Proportional Rate Reduction for TCP.

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Date:	Fri, 19 Aug 2011 03:26:51 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	nanditad@...gle.com
Cc:	netdev@...r.kernel.org, therbert@...gle.com, mattmathis@...gle.com,
	ycheng@...gle.com
Subject: Re: [PATCH v2] Proportional Rate Reduction for TCP.

From: Nandita Dukkipati <nanditad@...gle.com>
Date: Fri, 19 Aug 2011 00:33:32 -0700

> @@ -2830,9 +2830,14 @@ static int tcp_try_undo_loss(struct sock *sk)
>  static inline void tcp_complete_cwr(struct sock *sk)
>  {
>  	struct tcp_sock *tp = tcp_sk(sk);
> -	/* Do not moderate cwnd if it's already undone in cwr or recovery */
> -	if (tp->undo_marker && tp->snd_cwnd > tp->snd_ssthresh) {
> -		tp->snd_cwnd = tp->snd_ssthresh;
> +
> +	/* Do not moderate cwnd if it's already undone in cwr or recovery. */
> +	if (tp->undo_marker) {
> +
> +		if (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR)

Please get rid of that empty line before the TCP_CA_CWR case.

> +		sndcnt = DIV_ROUND_UP((u64)(tp->prr_delivered *
> +					    tp->snd_ssthresh),
> +				      (u64)tp->prior_cwnd) - tp->prr_out;

This won't link on 32-bit unless __divdi3 libgcc routine is provided
by the architecture.  To portably do 64-bit division you need to use
do_div() or something based upon it.  Perhaps DIV_ROUND_UP_LL() will
work best in this case.


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