commit 37b21591502d080b5f8ba9c1d0b37bd226b7f183 Author: Mike Perry mikeperry-git@torproject.org Date: Tue Oct 20 10:50:27 2020 -0500

Completely ignore abandoned circs from circ timeout calc

This prevents the timeout curve from getting spread out as much, resulting in more accurate timeout values for quantiles from 60-80. --- src/core/or/circuitstats.c | 64 ++++++++++------------------------------------ src/test/test.c | 10 +------- 2 files changed, 15 insertions(+), 59 deletions(-)

diff --git a/src/core/or/circuitstats.c b/src/core/or/circuitstats.c index 2cde21fa1f..d4eb23c966 100644 --- a/src/core/or/circuitstats.c +++ b/src/core/or/circuitstats.c @@ -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;

diff --git a/src/test/test.c b/src/test/test.c index 58b468775c..cd21a37409 100644 --- a/src/test/test.c +++ b/src/test/test.c @@ -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,