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Differential D20549 Diff 58355 sys/netinet/cc/cc_dctcp.c

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sys/netinet/cc/cc_dctcp.c

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#include <net/vnet.h> #include <net/vnet.h>
#include <netinet/tcp.h> #include <netinet/tcp.h>
#include <netinet/tcp_seq.h> #include <netinet/tcp_seq.h>
#include <netinet/tcp_var.h> #include <netinet/tcp_var.h>
#include <netinet/cc/cc.h> #include <netinet/cc/cc.h>
#include <netinet/cc/cc_module.h> #include <netinet/cc/cc_module.h>
#define MAX_ALPHA_VALUE 1024 #define DCTCP_SHIFT 10
#define MAX_ALPHA_VALUE 1<<DCTCP_SHIFT
tuexenUnsubmitted
Done
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Please add parentheses around the expression.

tuexen: Please add parentheses around the expression.
VNET_DEFINE_STATIC(uint32_t, dctcp_alpha) = 0; VNET_DEFINE_STATIC(uint32_t, dctcp_alpha) = 0;
#define V_dctcp_alpha VNET(dctcp_alpha) #define V_dctcp_alpha VNET(dctcp_alpha)
VNET_DEFINE_STATIC(uint32_t, dctcp_shift_g) = 4; VNET_DEFINE_STATIC(uint32_t, dctcp_shift_g) = 4;
#define V_dctcp_shift_g VNET(dctcp_shift_g) #define V_dctcp_shift_g VNET(dctcp_shift_g)
VNET_DEFINE_STATIC(uint32_t, dctcp_slowstart) = 0; VNET_DEFINE_STATIC(uint32_t, dctcp_slowstart) = 0;
#define V_dctcp_slowstart VNET(dctcp_slowstart) #define V_dctcp_slowstart VNET(dctcp_slowstart)
struct dctcp { struct dctcp {
int bytes_ecn; /* # of marked bytes during a RTT */ uint32_t bytes_ecn; /* # of marked bytes during a RTT */
int bytes_total; /* # of acked bytes during a RTT */ uint32_t bytes_total; /* # of acked bytes during a RTT */
int alpha; /* the fraction of marked bytes */ int alpha; /* the fraction of marked bytes */
int ce_prev; /* CE state of the last segment */ int ce_prev; /* CE state of the last segment */
int save_sndnxt; /* end sequence number of the current window */ tcp_seq save_sndnxt; /* end sequence number of the current window */
int ece_curr; /* ECE flag in this segment */ int ece_curr; /* ECE flag in this segment */
int ece_prev; /* ECE flag in the last segment */ int ece_prev; /* ECE flag in the last segment */
uint32_t num_cong_events; /* # of congestion events */ uint32_t num_cong_events; /* # of congestion events */
}; };
static MALLOC_DEFINE(M_dctcp, "dctcp data", static MALLOC_DEFINE(M_dctcp, "dctcp data",
"Per connection data required for the dctcp algorithm"); "Per connection data required for the dctcp algorithm");
static void dctcp_ack_received(struct cc_var *ccv, uint16_t type); static void dctcp_ack_received(struct cc_var *ccv, uint16_t type);
static void dctcp_after_idle(struct cc_var *ccv); static void dctcp_after_idle(struct cc_var *ccv);
static void dctcp_cb_destroy(struct cc_var *ccv); static void dctcp_cb_destroy(struct cc_var *ccv);
▲ Show 20 Lines • Show All 120 Lines • ▼ Show 20 Linesdctcp_cb_init(struct cc_var *ccv)
* queueing delay at the switch. When alpha is set to 1, queueing delay * queueing delay at the switch. When alpha is set to 1, queueing delay
* is kept small. * is kept small.
* Throughput-sensitive applications should have alpha = 0 * Throughput-sensitive applications should have alpha = 0
* Latency-sensitive applications should have alpha = 1 * Latency-sensitive applications should have alpha = 1
* *
* Note: DCTCP draft suggests initial alpha to be 1 but we've decided to * Note: DCTCP draft suggests initial alpha to be 1 but we've decided to
* keep it 0 as default. * keep it 0 as default.
*/ */
dctcp_data->alpha = V_dctcp_alpha; dctcp_data->alpha = V_dctcp_alpha << DCTCP_SHIFT;
dctcp_data->save_sndnxt = 0; dctcp_data->save_sndnxt = 0;
dctcp_data->ce_prev = 0; dctcp_data->ce_prev = 0;
dctcp_data->ece_curr = 0; dctcp_data->ece_curr = 0;
dctcp_data->ece_prev = 0; dctcp_data->ece_prev = 0;
dctcp_data->num_cong_events = 0; dctcp_data->num_cong_events = 0;
ccv->cc_data = dctcp_data; ccv->cc_data = dctcp_data;
return (0); return (0);
▲ Show 20 Lines • Show All 143 Lines • ▼ Show 20 Linesdctcp_update_alpha(struct cc_var *ccv)
struct dctcp *dctcp_data; struct dctcp *dctcp_data;
int alpha_prev; int alpha_prev;
dctcp_data = ccv->cc_data; dctcp_data = ccv->cc_data;
alpha_prev = dctcp_data->alpha; alpha_prev = dctcp_data->alpha;
dctcp_data->bytes_total = max(dctcp_data->bytes_total, 1); dctcp_data->bytes_total = max(dctcp_data->bytes_total, 1);
/* /*
* Update alpha: alpha = (1 - g) * alpha + g * F. * Update alpha: alpha = (1 - g) * alpha + g * F.
ccUnsubmitted
Done
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To be consistent with the RFC, please also replace the 'F' with the 'M'.

cc: To be consistent with the RFC, please also replace the 'F' with the 'M'.
rscheffAuthorUnsubmitted
Done
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Done. (RFC8257, page 7)

rscheff: Done. (RFC8257, page 7)
* Here: * Here:
* g is weight factor * g is weight factor
* recommaded to be set to 1/16 * recommaded to be set to 1/16
* small g = slow convergence between competitive DCTCP flows * small g = slow convergence between competitive DCTCP flows
* large g = impacts low utilization of bandwidth at switches * large g = impacts low utilization of bandwidth at switches
* F is fraction of marked segments in last RTT * F is fraction of marked segments in last RTT
* updated every RTT * updated every RTT
* Alpha must be round to 0 - MAX_ALPHA_VALUE. * Alpha must be round to 0 - MAX_ALPHA_VALUE.
*/ */
dctcp_data->alpha = min(alpha_prev - (alpha_prev >> V_dctcp_shift_g) + dctcp_data->alpha = ulmin(alpha_prev - (alpha_prev >> V_dctcp_shift_g) +
(dctcp_data->bytes_ecn << (10 - V_dctcp_shift_g)) / ((uint64_t)dctcp_data->bytes_ecn << (DCTCP_SHIFT - V_dctcp_shift_g)) /
dctcp_data->bytes_total, MAX_ALPHA_VALUE); dctcp_data->bytes_total, MAX_ALPHA_VALUE);
/* Initialize internal parameters for next alpha calculation */ /* Initialize internal parameters for next alpha calculation */
dctcp_data->bytes_ecn = 0; dctcp_data->bytes_ecn = 0;
dctcp_data->bytes_total = 0; dctcp_data->bytes_total = 0;
dctcp_data->save_sndnxt = CCV(ccv, snd_nxt); dctcp_data->save_sndnxt = CCV(ccv, snd_nxt);
} }
static int static int
dctcp_alpha_handler(SYSCTL_HANDLER_ARGS) dctcp_alpha_handler(SYSCTL_HANDLER_ARGS)
{ {
uint32_t new; uint32_t new;
int error; int error;
new = V_dctcp_alpha; new = V_dctcp_alpha;
error = sysctl_handle_int(oidp, &new, 0, req); error = sysctl_handle_int(oidp, &new, 0, req);
if (error == 0 && req->newptr != NULL) { if (error == 0 && req->newptr != NULL) {
if (new > 1) if ((new < 0) || (new > 1))
tuexenUnsubmitted
Done
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new is declared as uint32_t. So it can't be negative.
Either remove the check (and catch negative numbers provided in the sysctl command by the new > MAX_ALPHA_VALUE check) or declare it as int.

tuexen: `new` is declared as `uint32_t`. So it can't be negative. Either remove the check (and catch…
rscheffAuthorUnsubmitted
Done
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Checked the SYSCTL utility functions; apparently, with the CTLTYPE_UINT, negative input strings are discarded there, so no need to check here again. The handler is only called once these basic checks succeed. Thus removing the check for negatives here.

rscheff: Checked the SYSCTL utility functions; apparently, with the CTLTYPE_UINT, negative input strings…
error = EINVAL; error = EINVAL;
else {
if (new > MAX_ALPHA_VALUE)
V_dctcp_alpha = MAX_ALPHA_VALUE;
else else
V_dctcp_alpha = new; V_dctcp_alpha = new;
} }
}
return (error); return (error);
} }
static int static int
dctcp_shift_g_handler(SYSCTL_HANDLER_ARGS) dctcp_shift_g_handler(SYSCTL_HANDLER_ARGS)
{ {
uint32_t new; uint32_t new;
int error; int error;
new = V_dctcp_shift_g; new = V_dctcp_shift_g;
error = sysctl_handle_int(oidp, &new, 0, req); error = sysctl_handle_int(oidp, &new, 0, req);
if (error == 0 && req->newptr != NULL) { if (error == 0 && req->newptr != NULL) {
if (new > 1) if ((new < 0) || (new > DCTCP_SHIFT))
tuexenUnsubmitted
Done
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Same as in dctcp_alpha_handler().

tuexen: Same as in `dctcp_alpha_handler()`.
error = EINVAL; error = EINVAL;
else else
V_dctcp_shift_g = new; V_dctcp_shift_g = new;
} }
return (error); return (error);
} }
static int static int
dctcp_slowstart_handler(SYSCTL_HANDLER_ARGS) dctcp_slowstart_handler(SYSCTL_HANDLER_ARGS)
{ {
uint32_t new; uint32_t new;
int error; int error;
new = V_dctcp_slowstart; new = V_dctcp_slowstart;
error = sysctl_handle_int(oidp, &new, 0, req); error = sysctl_handle_int(oidp, &new, 0, req);
if (error == 0 && req->newptr != NULL) { if (error == 0 && req->newptr != NULL) {
if (new > 1) if ((new < 0) || (new > 1))
tuexenUnsubmitted
Done
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Same as in dctcp_alpha_handler().

tuexen: Same as in `dctcp_alpha_handler()`.
error = EINVAL; error = EINVAL;
else else
V_dctcp_slowstart = new; V_dctcp_slowstart = new;
} }
return (error); return (error);
} }
SYSCTL_DECL(_net_inet_tcp_cc_dctcp); SYSCTL_DECL(_net_inet_tcp_cc_dctcp);
SYSCTL_NODE(_net_inet_tcp_cc, OID_AUTO, dctcp, CTLFLAG_RW, NULL, SYSCTL_NODE(_net_inet_tcp_cc, OID_AUTO, dctcp, CTLFLAG_RW, NULL,
"dctcp congestion control related settings"); "dctcp congestion control related settings");
SYSCTL_PROC(_net_inet_tcp_cc_dctcp, OID_AUTO, alpha, SYSCTL_PROC(_net_inet_tcp_cc_dctcp, OID_AUTO, alpha,
CTLFLAG_VNET|CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(dctcp_alpha), 0, CTLFLAG_VNET|CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(dctcp_alpha), 0,
&dctcp_alpha_handler, &dctcp_alpha_handler,
"IU", "dctcp alpha parameter"); "IU", "dctcp alpha parameter at start of session");
SYSCTL_PROC(_net_inet_tcp_cc_dctcp, OID_AUTO, shift_g, SYSCTL_PROC(_net_inet_tcp_cc_dctcp, OID_AUTO, shift_g,
CTLFLAG_VNET|CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(dctcp_shift_g), 4, CTLFLAG_VNET|CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(dctcp_shift_g), 4,
&dctcp_shift_g_handler, &dctcp_shift_g_handler,
"IU", "dctcp shift parameter"); "IU", "dctcp shift parameter");
SYSCTL_PROC(_net_inet_tcp_cc_dctcp, OID_AUTO, slowstart, SYSCTL_PROC(_net_inet_tcp_cc_dctcp, OID_AUTO, slowstart,
CTLFLAG_VNET|CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(dctcp_slowstart), 0, CTLFLAG_VNET|CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(dctcp_slowstart), 0,
&dctcp_slowstart_handler, &dctcp_slowstart_handler,
"IU", "half CWND reduction after the first slow start"); "IU", "half CWND reduction after the first slow start");
DECLARE_CC_MODULE(dctcp, &dctcp_cc_algo); DECLARE_CC_MODULE(dctcp, &dctcp_cc_algo);