[TCP]: Remove TCP Compound (c427d274) · Commits · e / devices / android_kernel_xiaomi_nabu

net/ipv4/Kconfig

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		@@ -572,16 +572,6 @@ config TCP_CONG_VENO
		loss packets.
		See http://www.ntu.edu.sg/home5/ZHOU0022/papers/CPFu03a.pdf

		config TCP_CONG_COMPOUND
		tristate "TCP Compound"
		depends on EXPERIMENTAL
		default n
		---help---
		TCP Compound is a sender-side only change to TCP that uses
		a mixed Reno/Vegas approach to calculate the cwnd.
		For further details look here:
		ftp://ftp.research.microsoft.com/pub/tr/TR-2005-86.pdf

		endmenu

		config TCP_CONG_BIC

net/ipv4/Makefile

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Original line number	Diff line number	Diff line
		@@ -47,7 +47,6 @@ obj-$(CONFIG_TCP_CONG_VEGAS) += tcp_vegas.o
		obj-$(CONFIG_TCP_CONG_VENO) += tcp_veno.o
		obj-$(CONFIG_TCP_CONG_SCALABLE) += tcp_scalable.o
		obj-$(CONFIG_TCP_CONG_LP) += tcp_lp.o
		obj-$(CONFIG_TCP_CONG_COMPOUND) += tcp_compound.o

		obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \
		xfrm4_output.o

net/ipv4/tcp_compound.c

deleted100644 → 0

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		/*
		* TCP Vegas congestion control
		*
		* This is based on the congestion detection/avoidance scheme described in
		* Lawrence S. Brakmo and Larry L. Peterson.
		* "TCP Vegas: End to end congestion avoidance on a global internet."
		* IEEE Journal on Selected Areas in Communication, 13(8):1465--1480,
		* October 1995. Available from:
		* ftp://ftp.cs.arizona.edu/xkernel/Papers/jsac.ps
		*
		* See http://www.cs.arizona.edu/xkernel/ for their implementation.
		* The main aspects that distinguish this implementation from the
		* Arizona Vegas implementation are:
		* o We do not change the loss detection or recovery mechanisms of
		* Linux in any way. Linux already recovers from losses quite well,
		* using fine-grained timers, NewReno, and FACK.
		* o To avoid the performance penalty imposed by increasing cwnd
		* only every-other RTT during slow start, we increase during
		* every RTT during slow start, just like Reno.
		* o Largely to allow continuous cwnd growth during slow start,
		* we use the rate at which ACKs come back as the "actual"
		* rate, rather than the rate at which data is sent.
		* o To speed convergence to the right rate, we set the cwnd
		* to achieve the right ("actual") rate when we exit slow start.
		* o To filter out the noise caused by delayed ACKs, we use the
		* minimum RTT sample observed during the last RTT to calculate
		* the actual rate.
		* o When the sender re-starts from idle, it waits until it has
		* received ACKs for an entire flight of new data before making
		* a cwnd adjustment decision. The original Vegas implementation
		* assumed senders never went idle.
		*
		*
		* TCP Compound based on TCP Vegas
		*
		* further details can be found here:
		* ftp://ftp.research.microsoft.com/pub/tr/TR-2005-86.pdf
		*/

		#include <linux/config.h>
		#include <linux/mm.h>
		#include <linux/module.h>
		#include <linux/skbuff.h>
		#include <linux/inet_diag.h>

		#include <net/tcp.h>

		/* Default values of the Vegas variables, in fixed-point representation
		* with V_PARAM_SHIFT bits to the right of the binary point.
		*/
		#define V_PARAM_SHIFT 1

		#define TCP_COMPOUND_ALPHA 3U
		#define TCP_COMPOUND_BETA 1U
		#define TCP_COMPOUND_GAMMA 30
		#define TCP_COMPOUND_ZETA 1

		/* TCP compound variables */
		struct compound {
		u32 beg_snd_nxt; /* right edge during last RTT */
		u32 beg_snd_una; /* left edge during last RTT */
		u32 beg_snd_cwnd; /* saves the size of the cwnd */
		u8 doing_vegas_now; /* if true, do vegas for this RTT */
		u16 cntRTT; /* # of RTTs measured within last RTT */
		u32 minRTT; /* min of RTTs measured within last RTT (in usec) */
		u32 baseRTT; /* the min of all Vegas RTT measurements seen (in usec) */

		u32 cwnd;
		u32 dwnd;
		};

		/* There are several situations when we must "re-start" Vegas:
		*
		* o when a connection is established
		* o after an RTO
		* o after fast recovery
		* o when we send a packet and there is no outstanding
		* unacknowledged data (restarting an idle connection)
		*
		* In these circumstances we cannot do a Vegas calculation at the
		* end of the first RTT, because any calculation we do is using
		* stale info -- both the saved cwnd and congestion feedback are
		* stale.
		*
		* Instead we must wait until the completion of an RTT during
		* which we actually receive ACKs.
		*/
		static inline void vegas_enable(struct sock *sk)
		{
		const struct tcp_sock *tp = tcp_sk(sk);
		struct compound *vegas = inet_csk_ca(sk);

		/* Begin taking Vegas samples next time we send something. */
		vegas->doing_vegas_now = 1;

		/* Set the beginning of the next send window. */
		vegas->beg_snd_nxt = tp->snd_nxt;

		vegas->cntRTT = 0;
		vegas->minRTT = 0x7fffffff;
		}

		/* Stop taking Vegas samples for now. */
		static inline void vegas_disable(struct sock *sk)
		{
		struct compound *vegas = inet_csk_ca(sk);

		vegas->doing_vegas_now = 0;
		}

		static void tcp_compound_init(struct sock *sk)
		{
		struct compound *vegas = inet_csk_ca(sk);
		const struct tcp_sock *tp = tcp_sk(sk);

		vegas->baseRTT = 0x7fffffff;
		vegas_enable(sk);

		vegas->dwnd = 0;
		vegas->cwnd = tp->snd_cwnd;
		}

		/* Do RTT sampling needed for Vegas.
		* Basically we:
		* o min-filter RTT samples from within an RTT to get the current
		* propagation delay + queuing delay (we are min-filtering to try to
		* avoid the effects of delayed ACKs)
		* o min-filter RTT samples from a much longer window (forever for now)
		* to find the propagation delay (baseRTT)
		*/
		static void tcp_compound_rtt_calc(struct sock *sk, u32 usrtt)
		{
		struct compound *vegas = inet_csk_ca(sk);
		u32 vrtt = usrtt + 1; /* Never allow zero rtt or baseRTT */

		/* Filter to find propagation delay: */
		if (vrtt < vegas->baseRTT)
		vegas->baseRTT = vrtt;

		/* Find the min RTT during the last RTT to find
		* the current prop. delay + queuing delay:
		*/

		vegas->minRTT = min(vegas->minRTT, vrtt);
		vegas->cntRTT++;
		}

		static void tcp_compound_state(struct sock *sk, u8 ca_state)
		{

		if (ca_state == TCP_CA_Open)
		vegas_enable(sk);
		else
		vegas_disable(sk);
		}


		/* 64bit divisor, dividend and result. dynamic precision */
		static inline u64 div64_64(u64 dividend, u64 divisor)
		{
		u32 d = divisor;

		if (divisor > 0xffffffffULL) {
		unsigned int shift = fls(divisor >> 32);

		d = divisor >> shift;
		dividend >>= shift;
		}

		/* avoid 64 bit division if possible */
		if (dividend >> 32)
		do_div(dividend, d);
		else
		dividend = (u32) dividend / d;

		return dividend;
		}

		/* calculate the quartic root of "a" using Newton-Raphson */
		static u32 qroot(u64 a)
		{
		u32 x, x1;

		/* Initial estimate is based on:
		* qrt(x) = exp(log(x) / 4)
		*/
		x = 1u << (fls64(a) >> 2);

		/*
		* Iteration based on:
		* 3
		* x = ( 3 * x + a / x ) / 4
		* k+1 k k
		*/
		do {
		u64 x3 = x;

		x1 = x;
		x3 *= x;
		x3 *= x;

		x = (3 * x + (u32) div64_64(a, x3)) / 4;
		} while (abs(x1 - x) > 1);

		return x;
		}


		/*
		* If the connection is idle and we are restarting,
		* then we don't want to do any Vegas calculations
		* until we get fresh RTT samples. So when we
		* restart, we reset our Vegas state to a clean
		* slate. After we get acks for this flight of
		* packets, _then_ we can make Vegas calculations
		* again.
		*/
		static void tcp_compound_cwnd_event(struct sock *sk, enum tcp_ca_event event)
		{
		if (event == CA_EVENT_CWND_RESTART \|\| event == CA_EVENT_TX_START)
		tcp_compound_init(sk);
		}

		static void tcp_compound_cong_avoid(struct sock *sk, u32 ack,
		u32 seq_rtt, u32 in_flight, int flag)
		{
		struct tcp_sock *tp = tcp_sk(sk);
		struct compound *vegas = inet_csk_ca(sk);
		u8 inc = 0;

		if (vegas->cwnd + vegas->dwnd > tp->snd_cwnd) {
		if (vegas->cwnd > tp->snd_cwnd \|\| vegas->dwnd > tp->snd_cwnd) {
		vegas->cwnd = tp->snd_cwnd;
		vegas->dwnd = 0;
		} else
		vegas->cwnd = tp->snd_cwnd - vegas->dwnd;

		}

		if (!tcp_is_cwnd_limited(sk, in_flight))
		return;

		if (vegas->cwnd <= tp->snd_ssthresh)
		inc = 1;
		else if (tp->snd_cwnd_cnt < tp->snd_cwnd)
		tp->snd_cwnd_cnt++;

		if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
		inc = 1;
		tp->snd_cwnd_cnt = 0;
		}

		if (inc && tp->snd_cwnd < tp->snd_cwnd_clamp)
		vegas->cwnd++;

		/* The key players are v_beg_snd_una and v_beg_snd_nxt.
		*
		* These are so named because they represent the approximate values
		* of snd_una and snd_nxt at the beginning of the current RTT. More
		* precisely, they represent the amount of data sent during the RTT.
		* At the end of the RTT, when we receive an ACK for v_beg_snd_nxt,
		* we will calculate that (v_beg_snd_nxt - v_beg_snd_una) outstanding
		* bytes of data have been ACKed during the course of the RTT, giving
		* an "actual" rate of:
		*
		* (v_beg_snd_nxt - v_beg_snd_una) / (rtt duration)
		*
		* Unfortunately, v_beg_snd_una is not exactly equal to snd_una,
		* because delayed ACKs can cover more than one segment, so they
		* don't line up nicely with the boundaries of RTTs.
		*
		* Another unfortunate fact of life is that delayed ACKs delay the
		* advance of the left edge of our send window, so that the number
		* of bytes we send in an RTT is often less than our cwnd will allow.
		* So we keep track of our cwnd separately, in v_beg_snd_cwnd.
		*/

		if (after(ack, vegas->beg_snd_nxt)) {
		/* Do the Vegas once-per-RTT cwnd adjustment. */
		u32 old_wnd, old_snd_cwnd;

		/* Here old_wnd is essentially the window of data that was
		* sent during the previous RTT, and has all
		* been acknowledged in the course of the RTT that ended
		* with the ACK we just received. Likewise, old_snd_cwnd
		* is the cwnd during the previous RTT.
		*/
		if (!tp->mss_cache)
		return;

		old_wnd = (vegas->beg_snd_nxt - vegas->beg_snd_una) /
		tp->mss_cache;
		old_snd_cwnd = vegas->beg_snd_cwnd;

		/* Save the extent of the current window so we can use this
		* at the end of the next RTT.
		*/
		vegas->beg_snd_una = vegas->beg_snd_nxt;
		vegas->beg_snd_nxt = tp->snd_nxt;
		vegas->beg_snd_cwnd = tp->snd_cwnd;

		/* We do the Vegas calculations only if we got enough RTT
		* samples that we can be reasonably sure that we got
		* at least one RTT sample that wasn't from a delayed ACK.
		* If we only had 2 samples total,
		* then that means we're getting only 1 ACK per RTT, which
		* means they're almost certainly delayed ACKs.
		* If we have 3 samples, we should be OK.
		*/

		if (vegas->cntRTT > 2) {
		u32 rtt, target_cwnd, diff;
		u32 brtt, dwnd;

		/* We have enough RTT samples, so, using the Vegas
		* algorithm, we determine if we should increase or
		* decrease cwnd, and by how much.
		*/

		/* Pluck out the RTT we are using for the Vegas
		* calculations. This is the min RTT seen during the
		* last RTT. Taking the min filters out the effects
		* of delayed ACKs, at the cost of noticing congestion
		* a bit later.
		*/
		rtt = vegas->minRTT;

		/* Calculate the cwnd we should have, if we weren't
		* going too fast.
		*
		* This is:
		* (actual rate in segments) * baseRTT
		* We keep it as a fixed point number with
		* V_PARAM_SHIFT bits to the right of the binary point.
		*/
		if (!rtt)
		return;

		brtt = vegas->baseRTT;
		target_cwnd = ((old_wnd * brtt)
		<< V_PARAM_SHIFT) / rtt;

		/* Calculate the difference between the window we had,
		* and the window we would like to have. This quantity
		* is the "Diff" from the Arizona Vegas papers.
		*
		* Again, this is a fixed point number with
		* V_PARAM_SHIFT bits to the right of the binary
		* point.
		*/

		diff = (old_wnd << V_PARAM_SHIFT) - target_cwnd;

		dwnd = vegas->dwnd;

		if (diff < (TCP_COMPOUND_GAMMA << V_PARAM_SHIFT)) {
		u64 v;
		u32 x;

		/*
		* The TCP Compound paper describes the choice
		* of "k" determines the agressiveness,
		* ie. slope of the response function.
		*
		* For same value as HSTCP would be 0.8
		* but for computaional reasons, both the
		* original authors and this implementation
		* use 0.75.
		*/
		v = old_wnd;
		x = qroot(v * v * v) >> TCP_COMPOUND_ALPHA;
		if (x > 1)
		dwnd = x - 1;
		else
		dwnd = 0;

		dwnd += vegas->dwnd;

		} else if ((dwnd << V_PARAM_SHIFT) <
		(diff * TCP_COMPOUND_BETA))
		dwnd = 0;
		else
		dwnd =
		((dwnd << V_PARAM_SHIFT) -
		(diff *
		TCP_COMPOUND_BETA)) >> V_PARAM_SHIFT;

		vegas->dwnd = dwnd;

		}

		/* Wipe the slate clean for the next RTT. */
		vegas->cntRTT = 0;
		vegas->minRTT = 0x7fffffff;
		}

		tp->snd_cwnd = vegas->cwnd + vegas->dwnd;
		}

		/* Extract info for Tcp socket info provided via netlink. */
		static void tcp_compound_get_info(struct sock sk, u32 ext, struct sk_buff skb)
		{
		const struct compound *ca = inet_csk_ca(sk);
		if (ext & (1 << (INET_DIAG_VEGASINFO - 1))) {
		struct tcpvegas_info *info;

		info = RTA_DATA(__RTA_PUT(skb, INET_DIAG_VEGASINFO,
		sizeof(*info)));

		info->tcpv_enabled = ca->doing_vegas_now;
		info->tcpv_rttcnt = ca->cntRTT;
		info->tcpv_rtt = ca->baseRTT;
		info->tcpv_minrtt = ca->minRTT;
		rtattr_failure:;
		}
		}

		static struct tcp_congestion_ops tcp_compound = {
		.init = tcp_compound_init,
		.ssthresh = tcp_reno_ssthresh,
		.cong_avoid = tcp_compound_cong_avoid,
		.rtt_sample = tcp_compound_rtt_calc,
		.set_state = tcp_compound_state,
		.cwnd_event = tcp_compound_cwnd_event,
		.get_info = tcp_compound_get_info,

		.owner = THIS_MODULE,
		.name = "compound",
		};

		static int __init tcp_compound_register(void)
		{
		BUG_ON(sizeof(struct compound) > ICSK_CA_PRIV_SIZE);
		tcp_register_congestion_control(&tcp_compound);
		return 0;
		}

		static void __exit tcp_compound_unregister(void)
		{
		tcp_unregister_congestion_control(&tcp_compound);
		}

		module_init(tcp_compound_register);
		module_exit(tcp_compound_unregister);

		MODULE_AUTHOR("Angelo P. Castellani, Stephen Hemminger");
		MODULE_LICENSE("GPL");
		MODULE_DESCRIPTION("TCP Compound");