diff options
Diffstat (limited to 'sys/netinet/cc/cc_dctcp.c')
-rw-r--r-- | sys/netinet/cc/cc_dctcp.c | 474 |
1 files changed, 474 insertions, 0 deletions
diff --git a/sys/netinet/cc/cc_dctcp.c b/sys/netinet/cc/cc_dctcp.c new file mode 100644 index 0000000..93eb495 --- /dev/null +++ b/sys/netinet/cc/cc_dctcp.c @@ -0,0 +1,474 @@ +/*- + * Copyright (c) 2007-2008 + * Swinburne University of Technology, Melbourne, Australia + * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org> + * Copyright (c) 2014 Midori Kato <katoon@sfc.wide.ad.jp> + * Copyright (c) 2014 The FreeBSD Foundation + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +/* + * An implementation of the DCTCP algorithm for FreeBSD, based on + * "Data Center TCP (DCTCP)" by M. Alizadeh, A. Greenberg, D. A. Maltz, + * J. Padhye, P. Patel, B. Prabhakar, S. Sengupta, and M. Sridharan., + * in ACM Conference on SIGCOMM 2010, New York, USA, + * Originally released as the contribution of Microsoft Research project. + */ + +#include <sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include <sys/param.h> +#include <sys/kernel.h> +#include <sys/malloc.h> +#include <sys/module.h> +#include <sys/socket.h> +#include <sys/socketvar.h> +#include <sys/sysctl.h> +#include <sys/systm.h> + +#include <net/vnet.h> + +#include <netinet/in.h> +#include <netinet/ip.h> +#include <netinet/cc.h> +#include <netinet/tcp_seq.h> +#include <netinet/tcp_var.h> + +#include <netinet/cc/cc_module.h> + +#define CAST_PTR_INT(X) (*((int*)(X))) + +#define MAX_ALPHA_VALUE 1024 +static VNET_DEFINE(uint32_t, dctcp_alpha) = 0; +#define V_dctcp_alpha VNET(dctcp_alpha) +static VNET_DEFINE(uint32_t, dctcp_shift_g) = 4; +#define V_dctcp_shift_g VNET(dctcp_shift_g) +static VNET_DEFINE(uint32_t, dctcp_slowstart) = 0; +#define V_dctcp_slowstart VNET(dctcp_slowstart) + +struct dctcp { + int bytes_ecn; /* # of marked bytes during a RTT */ + int bytes_total; /* # of acked bytes during a RTT */ + int alpha; /* the fraction of marked bytes */ + int ce_prev; /* CE state of the last segment */ + int save_sndnxt; /* end sequence number of the current window */ + int ece_curr; /* ECE flag in this segment */ + int ece_prev; /* ECE flag in the last segment */ + uint32_t num_cong_events; /* # of congestion events */ +}; + +static MALLOC_DEFINE(M_dctcp, "dctcp data", + "Per connection data required for the dctcp algorithm"); + +static void dctcp_ack_received(struct cc_var *ccv, uint16_t type); +static void dctcp_after_idle(struct cc_var *ccv); +static void dctcp_cb_destroy(struct cc_var *ccv); +static int dctcp_cb_init(struct cc_var *ccv); +static void dctcp_cong_signal(struct cc_var *ccv, uint32_t type); +static void dctcp_conn_init(struct cc_var *ccv); +static void dctcp_post_recovery(struct cc_var *ccv); +static void dctcp_ecnpkt_handler(struct cc_var *ccv); +static void dctcp_update_alpha(struct cc_var *ccv); + +struct cc_algo dctcp_cc_algo = { + .name = "dctcp", + .ack_received = dctcp_ack_received, + .cb_destroy = dctcp_cb_destroy, + .cb_init = dctcp_cb_init, + .cong_signal = dctcp_cong_signal, + .conn_init = dctcp_conn_init, + .post_recovery = dctcp_post_recovery, + .ecnpkt_handler = dctcp_ecnpkt_handler, + .after_idle = dctcp_after_idle, +}; + +static void +dctcp_ack_received(struct cc_var *ccv, uint16_t type) +{ + struct dctcp *dctcp_data; + int bytes_acked = 0; + + dctcp_data = ccv->cc_data; + + if (CCV(ccv, t_flags) & TF_ECN_PERMIT) { + /* + * DCTCP doesn't treat receipt of ECN marked packet as a + * congestion event. Thus, DCTCP always executes the ACK + * processing out of congestion recovery. + */ + if (IN_CONGRECOVERY(CCV(ccv, t_flags))) { + EXIT_CONGRECOVERY(CCV(ccv, t_flags)); + newreno_cc_algo.ack_received(ccv, type); + ENTER_CONGRECOVERY(CCV(ccv, t_flags)); + } else + newreno_cc_algo.ack_received(ccv, type); + + if (type == CC_DUPACK) + bytes_acked = CCV(ccv, t_maxseg); + + if (type == CC_ACK) + bytes_acked = ccv->bytes_this_ack; + + /* Update total bytes. */ + dctcp_data->bytes_total += bytes_acked; + + /* Update total marked bytes. */ + if (dctcp_data->ece_curr) { + if (!dctcp_data->ece_prev + && bytes_acked > CCV(ccv, t_maxseg)) { + dctcp_data->bytes_ecn += + (bytes_acked - CCV(ccv, t_maxseg)); + } else + dctcp_data->bytes_ecn += bytes_acked; + dctcp_data->ece_prev = 1; + } else { + if (dctcp_data->ece_prev + && bytes_acked > CCV(ccv, t_maxseg)) + dctcp_data->bytes_ecn += CCV(ccv, t_maxseg); + dctcp_data->ece_prev = 0; + } + dctcp_data->ece_curr = 0; + + /* + * Update the fraction of marked bytes at the end of + * current window size. + */ + if ((IN_FASTRECOVERY(CCV(ccv, t_flags)) && + SEQ_GEQ(ccv->curack, CCV(ccv, snd_recover))) || + (!IN_FASTRECOVERY(CCV(ccv, t_flags)) && + SEQ_GT(ccv->curack, dctcp_data->save_sndnxt))) + dctcp_update_alpha(ccv); + } else + newreno_cc_algo.ack_received(ccv, type); +} + +static void +dctcp_after_idle(struct cc_var *ccv) +{ + struct dctcp *dctcp_data; + + dctcp_data = ccv->cc_data; + + /* Initialize internal parameters after idle time */ + dctcp_data->bytes_ecn = 0; + dctcp_data->bytes_total = 0; + dctcp_data->save_sndnxt = CCV(ccv, snd_nxt); + dctcp_data->alpha = V_dctcp_alpha; + dctcp_data->ece_curr = 0; + dctcp_data->ece_prev = 0; + dctcp_data->num_cong_events = 0; + + dctcp_cc_algo.after_idle = newreno_cc_algo.after_idle; +} + +static void +dctcp_cb_destroy(struct cc_var *ccv) +{ + if (ccv->cc_data != NULL) + free(ccv->cc_data, M_dctcp); +} + +static int +dctcp_cb_init(struct cc_var *ccv) +{ + struct dctcp *dctcp_data; + + dctcp_data = malloc(sizeof(struct dctcp), M_dctcp, M_NOWAIT|M_ZERO); + + if (dctcp_data == NULL) + return (ENOMEM); + + /* Initialize some key variables with sensible defaults. */ + dctcp_data->bytes_ecn = 0; + dctcp_data->bytes_total = 0; + /* + * When alpha is set to 0 in the beggining, DCTCP sender transfers as + * much data as possible until the value converges which may expand the + * queueing delay at the switch. When alpha is set to 1, queueing delay + * is kept small. + * Throughput-sensitive applications should have alpha = 0 + * Latency-sensitive applications should have alpha = 1 + * + * Note: DCTCP draft suggests initial alpha to be 1 but we've decided to + * keep it 0 as default. + */ + dctcp_data->alpha = V_dctcp_alpha; + dctcp_data->save_sndnxt = 0; + dctcp_data->ce_prev = 0; + dctcp_data->ece_curr = 0; + dctcp_data->ece_prev = 0; + dctcp_data->num_cong_events = 0; + + ccv->cc_data = dctcp_data; + return (0); +} + +/* + * Perform any necessary tasks before we enter congestion recovery. + */ +static void +dctcp_cong_signal(struct cc_var *ccv, uint32_t type) +{ + struct dctcp *dctcp_data; + u_int win, mss; + + dctcp_data = ccv->cc_data; + win = CCV(ccv, snd_cwnd); + mss = CCV(ccv, t_maxseg); + + switch (type) { + case CC_NDUPACK: + if (!IN_FASTRECOVERY(CCV(ccv, t_flags))) { + if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) { + CCV(ccv, snd_ssthresh) = mss * + max(win / 2 / mss, 2); + dctcp_data->num_cong_events++; + } else { + /* cwnd has already updated as congestion + * recovery. Reverse cwnd value using + * snd_cwnd_prev and recalculate snd_ssthresh + */ + win = CCV(ccv, snd_cwnd_prev); + CCV(ccv, snd_ssthresh) = + max(win / 2 / mss, 2) * mss; + } + ENTER_RECOVERY(CCV(ccv, t_flags)); + } + break; + case CC_ECN: + /* + * Save current snd_cwnd when the host encounters both + * congestion recovery and fast recovery. + */ + CCV(ccv, snd_cwnd_prev) = win; + if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) { + if (V_dctcp_slowstart && + dctcp_data->num_cong_events++ == 0) { + CCV(ccv, snd_ssthresh) = + mss * max(win / 2 / mss, 2); + dctcp_data->alpha = MAX_ALPHA_VALUE; + dctcp_data->bytes_ecn = 0; + dctcp_data->bytes_total = 0; + dctcp_data->save_sndnxt = CCV(ccv, snd_nxt); + } else + CCV(ccv, snd_ssthresh) = max((win - ((win * + dctcp_data->alpha) >> 11)) / mss, 2) * mss; + CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh); + ENTER_CONGRECOVERY(CCV(ccv, t_flags)); + } + dctcp_data->ece_curr = 1; + break; + case CC_RTO: + if (CCV(ccv, t_flags) & TF_ECN_PERMIT) { + CCV(ccv, t_flags) |= TF_ECN_SND_CWR; + dctcp_update_alpha(ccv); + dctcp_data->save_sndnxt += CCV(ccv, t_maxseg); + dctcp_data->num_cong_events++; + } + break; + } +} + +static void +dctcp_conn_init(struct cc_var *ccv) +{ + struct dctcp *dctcp_data; + + dctcp_data = ccv->cc_data; + + if (CCV(ccv, t_flags) & TF_ECN_PERMIT) + dctcp_data->save_sndnxt = CCV(ccv, snd_nxt); +} + +/* + * Perform any necessary tasks before we exit congestion recovery. + */ +static void +dctcp_post_recovery(struct cc_var *ccv) +{ + dctcp_cc_algo.post_recovery = newreno_cc_algo.post_recovery; + + if (CCV(ccv, t_flags) & TF_ECN_PERMIT) + dctcp_update_alpha(ccv); +} + +/* + * Execute an additional ECN processing using ECN field in IP header and the CWR + * bit in TCP header. + * + * delay_ack == 0 - Delayed ACK disabled + * delay_ack == 1 - Delayed ACK enabled + */ + +static void +dctcp_ecnpkt_handler(struct cc_var *ccv) +{ + struct dctcp *dctcp_data; + uint32_t ccflag; + int delay_ack; + + dctcp_data = ccv->cc_data; + ccflag = ccv->flags; + delay_ack = 1; + + /* + * DCTCP responses an ACK immediately when the CE state + * in between this segment and the last segment is not same. + */ + if (ccflag & CCF_IPHDR_CE) { + if (!dctcp_data->ce_prev && (ccflag & CCF_DELACK)) + delay_ack = 0; + dctcp_data->ce_prev = 1; + CCV(ccv, t_flags) |= TF_ECN_SND_ECE; + } else { + if (dctcp_data->ce_prev && (ccflag & CCF_DELACK)) + delay_ack = 0; + dctcp_data->ce_prev = 0; + CCV(ccv, t_flags) &= ~TF_ECN_SND_ECE; + } + + /* DCTCP sets delayed ack when this segment sets the CWR flag. */ + if ((ccflag & CCF_DELACK) && (ccflag & CCF_TCPHDR_CWR)) + delay_ack = 1; + + if (delay_ack == 0) + ccv->flags |= CCF_ACKNOW; + else + ccv->flags &= ~CCF_ACKNOW; +} + +/* + * Update the fraction of marked bytes represented as 'alpha'. + * Also initialize several internal parameters at the end of this function. + */ +static void +dctcp_update_alpha(struct cc_var *ccv) +{ + struct dctcp *dctcp_data; + int alpha_prev; + + dctcp_data = ccv->cc_data; + alpha_prev = dctcp_data->alpha; + dctcp_data->bytes_total = max(dctcp_data->bytes_total, 1); + + /* + * Update alpha: alpha = (1 - g) * alpha + g * F. + * Here: + * g is weight factor + * recommaded to be set to 1/16 + * small g = slow convergence between competitive DCTCP flows + * large g = impacts low utilization of bandwidth at switches + * F is fraction of marked segments in last RTT + * updated every RTT + * Alpha must be round to 0 - MAX_ALPHA_VALUE. + */ + dctcp_data->alpha = min(alpha_prev - (alpha_prev >> V_dctcp_shift_g) + + (dctcp_data->bytes_ecn << (10 - V_dctcp_shift_g)) / + dctcp_data->bytes_total, MAX_ALPHA_VALUE); + + /* Initialize internal parameters for next alpha calculation */ + dctcp_data->bytes_ecn = 0; + dctcp_data->bytes_total = 0; + dctcp_data->save_sndnxt = CCV(ccv, snd_nxt); +} + +static int +dctcp_alpha_handler(SYSCTL_HANDLER_ARGS) +{ + uint32_t new; + int error; + + new = V_dctcp_alpha; + error = sysctl_handle_int(oidp, &new, 0, req); + if (error == 0 && req->newptr != NULL) { + if (CAST_PTR_INT(req->newptr) > 1) + error = EINVAL; + else { + if (new > MAX_ALPHA_VALUE) + V_dctcp_alpha = MAX_ALPHA_VALUE; + else + V_dctcp_alpha = new; + } + } + + return (error); +} + +static int +dctcp_shift_g_handler(SYSCTL_HANDLER_ARGS) +{ + uint32_t new; + int error; + + new = V_dctcp_shift_g; + error = sysctl_handle_int(oidp, &new, 0, req); + if (error == 0 && req->newptr != NULL) { + if (CAST_PTR_INT(req->newptr) > 1) + error = EINVAL; + else + V_dctcp_shift_g = new; + } + + return (error); +} + +static int +dctcp_slowstart_handler(SYSCTL_HANDLER_ARGS) +{ + uint32_t new; + int error; + + new = V_dctcp_slowstart; + error = sysctl_handle_int(oidp, &new, 0, req); + if (error == 0 && req->newptr != NULL) { + if (CAST_PTR_INT(req->newptr) > 1) + error = EINVAL; + else + V_dctcp_slowstart = new; + } + + return (error); +} + +SYSCTL_DECL(_net_inet_tcp_cc_dctcp); +SYSCTL_NODE(_net_inet_tcp_cc, OID_AUTO, dctcp, CTLFLAG_RW, NULL, + "dctcp congestion control related settings"); + +SYSCTL_PROC(_net_inet_tcp_cc_dctcp, OID_AUTO, alpha, + CTLFLAG_VNET|CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(dctcp_alpha), 0, + &dctcp_alpha_handler, + "IU", "dctcp alpha parameter"); + +SYSCTL_PROC(_net_inet_tcp_cc_dctcp, OID_AUTO, shift_g, + CTLFLAG_VNET|CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(dctcp_shift_g), 4, + &dctcp_shift_g_handler, + "IU", "dctcp shift parameter"); + +SYSCTL_PROC(_net_inet_tcp_cc_dctcp, OID_AUTO, slowstart, + CTLFLAG_VNET|CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(dctcp_slowstart), 0, + &dctcp_slowstart_handler, + "IU", "half CWND reduction after the first slow start"); + +DECLARE_CC_MODULE(dctcp, &dctcp_cc_algo); |