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Implement the pareto fitting and timeout calculating bits.

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This commit is contained in:
Mike Perry 2009-08-27 01:46:06 -07:00
parent 7750bee21d
commit 04414830fe
5 changed files with 243 additions and 81 deletions
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4
src/or/Makefile.am
View File

@ -41,14 +41,14 @@ AM_CPPFLAGS = -DSHARE_DATADIR="\"$(datadir)\"" \
tor_LDFLAGS = @TOR_LDFLAGS_zlib@ @TOR_LDFLAGS_openssl@ @TOR_LDFLAGS_libevent@
tor_LDADD = ../common/libor.a ../common/libor-crypto.a \
../common/libor-event.a \
-lz -levent -lssl -lcrypto @TOR_LIB_WS32@ @TOR_LIB_GDI@
-lz -lm -levent -lssl -lcrypto @TOR_LIB_WS32@ @TOR_LIB_GDI@
test_SOURCES = $(COMMON_SRC) test_data.c test.c
test_LDFLAGS = @TOR_LDFLAGS_zlib@ @TOR_LDFLAGS_openssl@ \
@TOR_LDFLAGS_libevent@
test_LDADD = ../common/libor.a ../common/libor-crypto.a \
../common/libor-event.a \
-lz -levent -lssl -lcrypto @TOR_LIB_WS32@ @TOR_LIB_GDI@
-lz -lm -levent -lssl -lcrypto @TOR_LIB_WS32@ @TOR_LIB_GDI@
noinst_HEADERS = or.h eventdns.h eventdns_tor.h micro-revision.i

259
src/or/circuitbuild.c
View File

@ -9,14 +9,23 @@
* \brief The actual details of building circuits.
**/
#include <math.h>
long int lround(double x);
double
ln(double x)
{
return log(x);
}
#undef log
#include "or.h"
#include "crypto.h"
/********* START VARIABLES **********/
/** Global list of circuit build times */
// XXX: Make this a smartlist..
uint16_t circuit_build_times[NCIRCUITS_TO_OBSERVE];
int build_times_idx = 0;
int total_build_times = 0;
circuit_build_times_t circ_times;
/** A global list of all circuits at this hop. */
extern circuit_t *global_circuitlist;
@ -65,25 +74,24 @@ static int onion_append_hop(crypt_path_t **head_ptr, extend_info_t *choice);
static void entry_guards_changed(void);
static time_t start_of_month(time_t when);
static int circuit_build_times_add_time(time_t time);
/** circuit_build_times is a circular array, so loop around when
/**
* circuit_build_times is a circular array, so loop around when
* array is full
*
* time units are milliseconds
*/
static
int
circuit_build_times_add_time(long time)
circuit_build_times_add_time(circuit_build_times_t *cbt, long time)
{
if (time > UINT16_MAX) {
log_notice(LD_CIRC,
"Circuit build time of %dms exceeds max. Capping at 65536ms", time);
"Circuit build time of %ldms exceeds max. Capping at 65536ms", time);
time = UINT16_MAX;
}
circuit_build_times[build_times_idx] = time;
build_times_idx = (build_times_idx + 1) % NCIRCUITS_TO_OBSERVE;
if(total_build_times + 1 < NCIRCUITS_TO_OBSERVE)
total_build_times++;
cbt->circuit_build_times[cbt->build_times_idx] = time;
cbt->build_times_idx = (cbt->build_times_idx + 1) % NCIRCUITS_TO_OBSERVE;
if (cbt->total_build_times + 1 < NCIRCUITS_TO_OBSERVE)
cbt->total_build_times++;
return 0;
}
@ -91,15 +99,16 @@ circuit_build_times_add_time(long time)
/**
* Calculate histogram
*/
void
circuit_build_times_create_histogram(uint16_t * histogram)
static void
circuit_build_times_create_histogram(circuit_build_times_t *cbt,
uint16_t *histogram)
{
int i, c;
// calculate histogram
for (i = 0; i < NCIRCUITS_TO_OBSERVE; i++) {
if(circuit_build_times[i] == 0) continue; /* 0 <-> uninitialized */
if (cbt->circuit_build_times[i] == 0) continue; /* 0 <-> uninitialized */
c = (circuit_build_times[i] / BUILDTIME_BIN_WIDTH);
c = (cbt->circuit_build_times[i] / BUILDTIME_BIN_WIDTH);
histogram[c]++;
}
}
@ -107,26 +116,29 @@ circuit_build_times_create_histogram(uint16_t * histogram)
/**
* Find maximum circuit build time
*/
uint16_t
circuit_build_times_max()
static uint16_t
circuit_build_times_max(circuit_build_times_t *cbt)
{
int i = 0, max_build_time = 0;
for (i = 0; i < NCIRCUITS_TO_OBSERVE; i++) {
if(circuit_build_times[i] > max_build_time)
max_build_time = circuit_build_times[i];
if (cbt->circuit_build_times[i] > max_build_time)
max_build_time = cbt->circuit_build_times[i];
}
return max_build_time;
}
uint16_t
circuit_build_times_min()
static uint16_t
circuit_build_times_min(circuit_build_times_t *cbt)
{
int i = 0;
uint16_t min_build_time = UINT16_MAX;
for (i = 0; i < NCIRCUITS_TO_OBSERVE; i++) {
if(circuit_build_times[i] && /* 0 <-> uninitialized */
circuit_build_times[i] < min_build_time)
min_build_time = circuit_build_times[i];
if (cbt->circuit_build_times[i] && /* 0 <-> uninitialized */
cbt->circuit_build_times[i] < min_build_time)
min_build_time = cbt->circuit_build_times[i];
}
if (min_build_time == UINT16_MAX) {
log_warn(LD_CIRC, "No build times less than UIN16_MAX!");
}
return min_build_time;
}
@ -135,31 +147,33 @@ circuit_build_times_min()
* output a histogram of current circuit build times
*/
void
circuit_build_times_update_state(or_state_t * state)
circuit_build_times_update_state(circuit_build_times_t *cbt,
or_state_t *state)
{
uint16_t max_build_time = 0, *histogram;
int i = 0, nbins = 0;
config_line_t **next, *line;
max_build_time = circuit_build_times_max();
max_build_time = circuit_build_times_max(cbt);
nbins = 1 + (max_build_time / BUILDTIME_BIN_WIDTH);
histogram = tor_malloc_zero(nbins * sizeof(uint16_t));
circuit_build_times_create_histogram(histogram);
circuit_build_times_create_histogram(cbt, histogram);
// write to state
config_free_lines(state->BuildtimeHistogram);
next = &state->BuildtimeHistogram;
*next = NULL;
state->TotalBuildTimes = total_build_times;
state->TotalBuildTimes = cbt->total_build_times;
// total build times?
for (i = 0; i < nbins; i++) {
if(histogram[i] == 0) continue; // compress the histogram by skipping the blanks
// compress the histogram by skipping the blanks
if (histogram[i] == 0) continue;
*next = line = tor_malloc_zero(sizeof(config_line_t));
line->key = tor_strdup("CircuitBuildTimeBin");
line->value = tor_malloc(20);
tor_snprintf(line->value, 20, "%d %d", i*BUILDTIME_BIN_WIDTH,
line->value = tor_malloc(25);
tor_snprintf(line->value, 25, "%d %d", i*BUILDTIME_BIN_WIDTH,
histogram[i]);
next = &(line->next);
}
@ -169,27 +183,16 @@ circuit_build_times_update_state(or_state_t * state)
if (histogram) tor_free(histogram);
}
int
find_next_available(int chosen)
{// find index of next open slot in circuit_build_times
int idx = 0;
for(idx = (chosen + 1) % NCIRCUITS_TO_OBSERVE; idx < chosen;
idx = ((idx + 1 ) % NCIRCUITS_TO_OBSERVE)) {
if(circuit_build_times[idx] == 0) {
return idx;
}
}
return 0;
}
/** Load histogram from state */
int
circuit_build_times_parse_state(or_state_t *state, char **msg)
circuit_build_times_parse_state(circuit_build_times_t *cbt,
or_state_t *state, char **msg)
{
int tot_values = 0, lines = 0;
config_line_t *line;
msg = NULL;
memset(circuit_build_times, 0, NCIRCUITS_TO_OBSERVE);
total_build_times = state->TotalBuildTimes;
memset(cbt->circuit_build_times, 0, NCIRCUITS_TO_OBSERVE);
cbt->total_build_times = state->TotalBuildTimes;
for (line = state->BuildtimeHistogram; line; line = line->next) {
smartlist_t * args = smartlist_create();
@ -200,20 +203,162 @@ circuit_build_times_parse_state(or_state_t *state, char **msg)
"Too few arguments to CircuitBuildTIme");
break;
} else {
uint16_t ms, count, i;
/* XXX: use tor_strtol */
ms = atol(smartlist_get(args,0));
count = atol(smartlist_get(args,1));
const char *ms_str = smartlist_get(args,0);
const char *count_str = smartlist_get(args,1);
uint32_t count, i;
uint16_t ms;
int ok;
ms = tor_parse_ulong(ms_str, 0, 0, UINT16_MAX, &ok, NULL);
if (!ok) {
*msg = tor_strdup("Unable to parse circuit build times: "
"Unparsable bin number");
break;
}
count = tor_parse_ulong(count_str, 0, 0, UINT32_MAX, &ok, NULL);
if (!ok) {
*msg = tor_strdup("Unable to parse circuit build times: "
"Unparsable bin count");
break;
}
lines++;
for (i = 0; i < count; i++) {
circuit_build_times_add_time(ms);
circuit_build_times_add_time(cbt, ms);
tot_values++;
}
}
}
log_info(LD_CIRC, "Loaded %d values from %d lines in circuit time histogram",
tot_values, lines);
circuit_build_times_set_timeout(cbt);
return (msg ? -1 : 0);
}
static void
circuit_build_times_update_alpha(circuit_build_times_t *cbt)
{
uint16_t *x=cbt->circuit_build_times;
double a = 0;
int n=0,i=0;
/* http://en.wikipedia.org/wiki/Pareto_distribution#Parameter_estimation */
cbt->Xm = circuit_build_times_min(cbt);
for (i=0; i< NCIRCUITS_TO_OBSERVE; i++) {
if (!x[i]) continue;
a += ln(x[i]);
n++;
}
tor_assert(n==cbt->total_build_times);
a -= n*ln(cbt->Xm);
a = n/a;
cbt->alpha = a;
}
/**
* This is the Pareto Quantile Function. It calculates the point x
* in the distribution such that F(x) < quantile (ie quantile*100%
* of the mass of the density function is below x on the curve).
*
* We use it to calculate the timeout and also synthetic values of
* time for circuits that timeout before completion.
*
* See http://en.wikipedia.org/wiki/Quantile_function,
* http://en.wikipedia.org/wiki/Inverse_transform_sampling and
* http://en.wikipedia.org/wiki/Pareto_distribution#Parameter_estimation
* That's right. I'll cite wikipedia all day long.
*/
static double
circuit_build_times_calculate_timeout(circuit_build_times_t *cbt,
double quantile)
{
return cbt->Xm/pow(1.0-quantile,1.0/cbt->alpha);
}
static void
circuit_build_times_add_timeout_worker(circuit_build_times_t *cbt)
{
/* Generate 0.8-1.0... */
uint64_t r = crypto_rand_uint64(UINT64_MAX-1);
double u = BUILDTIMEOUT_QUANTILE_CUTOFF +
((1.0-BUILDTIMEOUT_QUANTILE_CUTOFF)*r)/(1.0*UINT64_MAX);
long gentime = lround(circuit_build_times_calculate_timeout(cbt, u));
if (gentime < get_options()->CircuitBuildTimeout*1000) {
log_warn(LD_CIRC,
"Generated a synthetic timeout LESS than the current timeout: %ld vs %d",
gentime, get_options()->CircuitBuildTimeout*1000);
tor_assert(gentime >= get_options()->CircuitBuildTimeout*1000);
} else if (gentime > UINT16_MAX) {
gentime = UINT16_MAX;
log_info(LD_CIRC,
"Generated a synthetic timeout LESS than the current timeout: %ld vs %d",
gentime, get_options()->CircuitBuildTimeout*1000);
} else {
log_info(LD_CIRC, "Generated synthetic time %ld for timeout",
gentime);
}
circuit_build_times_add_time(cbt, gentime);
}
/**
* Store a timeout as a synthetic value
*/
void
circuit_build_times_add_timeout(circuit_build_times_t *cbt)
{
if (cbt->total_build_times < MIN_CIRCUITS_TO_OBSERVE) {
/* Store a timeout before we have enough data as special */
cbt->pre_timeouts++;
return;
}
/* Store a timeout as a random position on this curve */
if (cbt->pre_timeouts && get_options()->CircuitBuildTimeout != 60) {
cbt->Xm = circuit_build_times_min(cbt);
// Use current timeout to get an estimate on alpha
// Q(u) = Xm/((1-u)^(1/a))
// Q(0.8) = Xm/((1-0.8))^(1/a)) = CircBuildTimeout
// CircBuildTimeout = Xm/((1-0.8))^(1/a))
// CircBuildTimeout = Xm*((1-0.8))^(-1/a))
// ln(CircBuildTimeout) = ln(Xm)+ln(((1-0.8)))*(-1/a)
// -ln(1-0.8)/(ln(CircBuildTimeout)-ln(Xm))=a
cbt->alpha = -ln(1-BUILDTIMEOUT_QUANTILE_CUTOFF)/
(ln(get_options()->CircuitBuildTimeout)-ln(cbt->Xm));
while (cbt->pre_timeouts-- != 0) {
circuit_build_times_add_timeout_worker(cbt);
}
}
cbt->pre_timeouts = 0;
circuit_build_times_add_timeout_worker(cbt);
}
void
circuit_build_times_set_timeout(circuit_build_times_t *cbt)
{
double timeout;
if (cbt->total_build_times < MIN_CIRCUITS_TO_OBSERVE) {
log_info(LD_CIRC,
"Not enough circuits yet to calculate a new build timeout."
" Need %d more.",
MIN_CIRCUITS_TO_OBSERVE-cbt->total_build_times);
return;
}
circuit_build_times_update_alpha(cbt);
timeout = circuit_build_times_calculate_timeout(cbt,
BUILDTIMEOUT_QUANTILE_CUTOFF);
get_options()->CircuitBuildTimeout = lround(timeout/1000.0);
log_info(LD_CIRC,
"Set circuit build timeout to %d based on %d circuit times",
get_options()->CircuitBuildTimeout, cbt->total_build_times);
}
/** Iterate over values of circ_id, starting from conn-\>next_circ_id,
* and with the high bit specified by conn-\>circ_id_type, until we get
@ -800,9 +945,9 @@ circuit_send_next_onion_skin(origin_circuit_t *circ)
tor_gettimeofday(&end);
/* done building the circuit. whew. */
circuit_set_state(TO_CIRCUIT(circ), CIRCUIT_STATE_OPEN);
circuit_build_times_add_time(tor_mdiff(&circ->_base.timestamp_created,
&end));
circuit_build_times_recompute();
circuit_build_times_add_time(&circ_times,
tv_mdiff(&circ->_base.highres_created, &end));
circuit_build_times_set_timeout(&circ_times);
log_info(LD_CIRC,"circuit built!");
circuit_reset_failure_count(0);
if (circ->build_state->onehop_tunnel)

2
src/or/circuituse.c
View File

@ -358,6 +358,8 @@ circuit_expire_building(time_t now)
circuit_log_path(LOG_INFO,LD_CIRC,TO_ORIGIN_CIRCUIT(victim));
circuit_mark_for_close(victim, END_CIRC_REASON_TIMEOUT);
circuit_build_times_add_timeout(&circ_times);
circuit_build_times_set_timeout(&circ_times);
}
}

7
src/or/config.c
View File

@ -413,7 +413,6 @@ static config_var_t _state_vars[] = {
VAR("CircuitBuildTimeBin", LINELIST_S, BuildtimeHistogram, NULL),
VAR("BuildtimeHistogram", LINELIST_V, BuildtimeHistogram, NULL),
{ NULL, CONFIG_TYPE_OBSOLETE, 0, NULL }
};
@ -2923,7 +2922,7 @@ compute_publishserverdescriptor(or_options_t *options)
/** Lowest allowable value for CircuitBuildTimeout; values too low will
* increase network load because of failing connections being retried, and
* might prevent users from connecting to the network at all. */
#define MIN_CIRCUIT_BUILD_TIMEOUT 30
#define MIN_CIRCUIT_BUILD_TIMEOUT 5
/** Lowest allowable value for MaxCircuitDirtiness; if this is too low, Tor
* will generate too many circuits and potentially overload the network. */
@ -5070,7 +5069,7 @@ or_state_set(or_state_t *new_state)
tor_free(err);
}
if(circuit_build_times_parse_state(global_state, &err) < 0) {
if (circuit_build_times_parse_state(&circ_times, global_state, &err) < 0) {
log_warn(LD_GENERAL,"%s",err);
tor_free(err);
@ -5208,7 +5207,7 @@ or_state_save(time_t now)
* to avoid redundant writes. */
entry_guards_update_state(global_state);
rep_hist_update_state(global_state);
circuit_build_times_update_state(global_state);
circuit_build_times_update_state(&circ_times, global_state);
if (accounting_is_enabled(get_options()))
accounting_run_housekeeping(now);

26
src/or/or.h
View File

@ -1890,6 +1890,8 @@ typedef struct crypt_path_t {
#define NCIRCUITS_TO_OBSERVE 10000 /* approx 3 weeks worth of circuits */
#define BUILDTIME_BIN_WIDTH 50
/* TODO: This should be moved to the consensus */
#define BUILDTIMEOUT_QUANTILE_CUTOFF 0.8
/** Information used to build a circuit. */
typedef struct {
@ -1984,7 +1986,7 @@ typedef struct circuit_t {
time_t timestamp_created; /**< When was this circuit created? */
time_t timestamp_dirty; /**< When the circuit was first used, or 0 if the
* circuit is clean. */
struct timeval highres_created; /**< When exactly was this circuit created? */
struct timeval highres_created; /**< When exactly was the circuit created? */
uint16_t marked_for_close; /**< Should we close this circuit at the end of
* the main loop? (If true, holds the line number
@ -2695,7 +2697,6 @@ typedef struct {
config_line_t * BuildtimeHistogram;
uint16_t TotalBuildTimes;
/** What version of Tor wrote this state file? */
char *TorVersion;
@ -2865,10 +2866,25 @@ void bridges_retry_all(void);
void entry_guards_free_all(void);
void circuit_build_times_update_state(or_state_t *state);
int circuit_build_times_parse_state(or_state_t *state, char **msg);
/* Circuit Build Timeout "public" functions (I love C... No wait.) */
typedef struct {
// XXX: Make this a smartlist..
uint16_t circuit_build_times[NCIRCUITS_TO_OBSERVE];
int build_times_idx;
int total_build_times;
int pre_timeouts;
uint16_t Xm;
double alpha;
} circuit_build_times_t;
extern circuit_build_times_t circ_times;
void circuit_build_times_update_state(circuit_build_times_t *cbt,
or_state_t *state);
int circuit_build_times_parse_state(circuit_build_times_t *cbt,
or_state_t *state, char **msg);
void circuit_build_times_add_timeout(circuit_build_times_t *cbt);
void circuit_build_times_set_timeout(circuit_build_times_t *cbt);
int circuit_build_times_add_time(circuit_build_times_t *cbt, long time);
/********************************* circuitlist.c ***********************/