torproject/tor
1
0
Fork 0
mirror of https://gitlab.torproject.org/tpo/core/tor.git synced 2024-12-06 19:41:15 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity

Completely ignore abandoned circs from circ timeout calc

Browse Source 
This prevents the timeout curve from getting spread out as much, resulting in
more accurate timeout values for quantiles from 60-80.
This commit is contained in:
Mike Perry
2020-10-20 10:50:27 -05:00
parent 21317c9229
commit 37b2159150
2 changed files with 15 additions and 59 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/core/or/circuitstats.c
+14 -50
View File
@@ -1009,43 +1009,6 @@ circuit_build_times_shuffle_and_store_array(circuit_build_times_t *cbt,
}
}
/**
* Filter old synthetic timeouts that were created before the
* new right-censored Pareto calculation was deployed.
*
* Once all clients before 0.2.1.13-alpha are gone, this code
* will be unused.
*/
static int
circuit_build_times_filter_timeouts(circuit_build_times_t *cbt)
{
int num_filtered=0, i=0;
double timeout_rate = 0;
build_time_t max_timeout = 0;
timeout_rate = circuit_build_times_timeout_rate(cbt);
max_timeout = (build_time_t)cbt->close_ms;
for (i = 0; i < CBT_NCIRCUITS_TO_OBSERVE; i++) {
if (cbt->circuit_build_times[i] > max_timeout) {
build_time_t replaced = cbt->circuit_build_times[i];
num_filtered++;
cbt->circuit_build_times[i] = CBT_BUILD_ABANDONED;
log_debug(LD_CIRC, "Replaced timeout %d with %d", replaced,
cbt->circuit_build_times[i]);
}
}
log_info(LD_CIRC,
"We had %d timeouts out of %d build times, "
"and filtered %d above the max of %u",
(int)(cbt->total_build_times*timeout_rate),
cbt->total_build_times, num_filtered, max_timeout);
return num_filtered;
}
/**
* Load histogram from <b>state</b>, shuffling the resulting array
* after we do so. Use this result to estimate parameters and
@@ -1171,10 +1134,6 @@ circuit_build_times_parse_state(circuit_build_times_t *cbt,
circuit_build_times_set_timeout(cbt);
if (!state->CircuitBuildAbandonedCount && cbt->total_build_times) {
circuit_build_times_filter_timeouts(cbt);
}
done:
tor_free(loaded_times);
return err ? -1 : 0;
@@ -1215,14 +1174,15 @@ circuit_build_times_update_alpha(circuit_build_times_t *cbt)
if (x[i] < cbt->Xm) {
a += tor_mathlog(cbt->Xm);
n++;
} else if (x[i] == CBT_BUILD_ABANDONED) {
abandoned_count++;
} else {
a += tor_mathlog(x[i]);
if (x[i] > max_time)
max_time = x[i];
n++;
}
n++;
}
/*
@@ -1231,11 +1191,11 @@ circuit_build_times_update_alpha(circuit_build_times_t *cbt)
* performs this same check, and resets state if it hits it. If we
* hit it at runtime, something serious has gone wrong.
*/
if (n!=cbt->total_build_times) {
if (n!=cbt->total_build_times-abandoned_count) {
log_err(LD_CIRC, "Discrepancy in build times count: %d vs %d", n,
cbt->total_build_times);
}
tor_assert(n==cbt->total_build_times);
tor_assert_nonfatal(n==cbt->total_build_times-abandoned_count);
if (max_time <= 0) {
/* This can happen if Xm is actually the *maximum* value in the set.
@@ -1248,13 +1208,17 @@ circuit_build_times_update_alpha(circuit_build_times_t *cbt)
return 0;
}
a += abandoned_count*tor_mathlog(max_time);
/* This is the "Maximum Likelihood Estimator" for parameter alpha of a Pareto
* Distribution. See:
* https://en.wikipedia.org/wiki/Pareto_distribution#Estimation_of_parameters
*
* The division in the estimator is done with subtraction outside the ln(),
* with the sum occurring in the for loop above.
*
* This done is to avoid the precision issues of logs of small values.
*/
a -= n*tor_mathlog(cbt->Xm);
// Estimator comes from Eq #4 in:
// "Bayesian estimation based on trimmed samples from Pareto populations"
// by Arturo J. Fernández. We are right-censored only.
a = (n-abandoned_count)/a;
a = n/a;
cbt->alpha = a;
src/test/test.c
+1 -9
View File
@@ -384,7 +384,6 @@ test_circuit_timeout(void *arg)
double timeout1, timeout2;
or_state_t *state=NULL;
int i, runs;
double close_ms;
(void)arg;
initialize_periodic_events();
@@ -406,18 +405,11 @@ test_circuit_timeout(void *arg)
circuit_build_times_initial_alpha(&initial,
CBT_DEFAULT_QUANTILE_CUTOFF/100.0,
timeout0);
close_ms = MAX(circuit_build_times_calculate_timeout(&initial,
CBT_DEFAULT_CLOSE_QUANTILE/100.0),
CBT_DEFAULT_TIMEOUT_INITIAL_VALUE);
do {
for (i=0; i < CBT_DEFAULT_MIN_CIRCUITS_TO_OBSERVE; i++) {
build_time_t sample = circuit_build_times_generate_sample(&initial,0,1);
if (sample > close_ms) {
circuit_build_times_add_time(&estimate, CBT_BUILD_ABANDONED);
} else {
circuit_build_times_add_time(&estimate, sample);
}
circuit_build_times_add_time(&estimate, sample);
}
circuit_build_times_update_alpha(&estimate);
timeout1 = circuit_build_times_calculate_timeout(&estimate,