commit 5e395ba2c2bf041cacf85e6ad38cb39ea8ae7419 Author: Nick Mathewson nickm@torproject.org Date: Thu Apr 26 10:18:39 2018 -0400
Rewrite time-handling in circuitmux_ewma to use monotime_coarse
This part of the code was the only part that used "cached getttimeofday" feature, which wasn't monotonic, which we updated at slight expense, and which I'd rather not maintain. --- changes/ticket25927.1 | 6 ++++ src/or/circuitmux_ewma.c | 79 ++++++++++++++++++++++++++++++++++------------ src/or/circuitmux_ewma.h | 7 ++++ src/or/main.c | 2 ++ src/test/test_channel.c | 2 ++ src/test/test_circuitmux.c | 40 +++++++++++++++++++++++ 6 files changed, 115 insertions(+), 21 deletions(-)
diff --git a/changes/ticket25927.1 b/changes/ticket25927.1 new file mode 100644 index 000000000..84ac86e18 --- /dev/null +++ b/changes/ticket25927.1 @@ -0,0 +1,6 @@ + o Minor features (timekeeping, circuit scheduling): + - When keeping track of how busy each circuit have been recently on + a given connection, use coarse-grained monotonic timers rather than + gettimeofday(). This change should marginally increase accuracy + and performance. Implements part of ticket 25927. + diff --git a/src/or/circuitmux_ewma.c b/src/or/circuitmux_ewma.c index 4b80124a7..a8a645ca5 100644 --- a/src/or/circuitmux_ewma.c +++ b/src/or/circuitmux_ewma.c @@ -28,7 +28,7 @@ * **/
-#define TOR_CIRCUITMUX_EWMA_C_ +#define CIRCUITMUX_EWMA_PRIVATE
#include "orconfig.h"
@@ -169,8 +169,6 @@ TO_EWMA_POL_CIRC_DATA(circuitmux_policy_circ_data_t *pol)
static void add_cell_ewma(ewma_policy_data_t *pol, cell_ewma_t *ewma); static int compare_cell_ewma_counts(const void *p1, const void *p2); -static unsigned cell_ewma_tick_from_timeval(const struct timeval *now, - double *remainder_out); static circuit_t * cell_ewma_to_circuit(cell_ewma_t *ewma); static inline double get_scale_factor(unsigned from_tick, unsigned to_tick); static cell_ewma_t * pop_first_cell_ewma(ewma_policy_data_t *pol); @@ -239,6 +237,13 @@ circuitmux_policy_t ewma_policy = { /*.cmp_cmux =*/ ewma_cmp_cmux };
+/** Have we initialized the ewma tick-counting logic? */ +static int ewma_ticks_initialized = 0; +/** At what monotime_coarse_t did the current tick begin? */ +static monotime_coarse_t start_of_current_tick; +/** What is the number of the current tick? */ +static unsigned current_tick_num; + /*** EWMA method implementations using the below EWMA helper functions ***/
/** Compute and return the current cell_ewma tick. */ @@ -421,8 +426,6 @@ ewma_notify_xmit_cells(circuitmux_t *cmux, ewma_policy_circ_data_t *cdata = NULL; unsigned int tick; double fractional_tick, ewma_increment; - /* The current (hi-res) time */ - struct timeval now_hires; cell_ewma_t *cell_ewma, *tmp;
tor_assert(cmux); @@ -435,8 +438,7 @@ ewma_notify_xmit_cells(circuitmux_t *cmux, cdata = TO_EWMA_POL_CIRC_DATA(pol_circ_data);
/* Rescale the EWMAs if needed */ - tor_gettimeofday_cached(&now_hires); - tick = cell_ewma_tick_from_timeval(&now_hires, &fractional_tick); + tick = cell_ewma_get_current_tick_and_fraction(&fractional_tick);
if (tick != pol->active_circuit_pqueue_last_recalibrated) { scale_active_circuits(pol, tick); @@ -597,24 +599,48 @@ cell_ewma_to_circuit(cell_ewma_t *ewma) rescale. */
-/** Given a timeval <b>now</b>, compute the cell_ewma tick in which it occurs - * and the fraction of the tick that has elapsed between the start of the tick - * and <b>now</b>. Return the former and store the latter in - * *<b>remainder_out</b>. +/** + * Initialize the system that tells which ewma tick we are in. + */ +STATIC void +cell_ewma_initialize_ticks(void) +{ + if (ewma_ticks_initialized) + return; + monotime_coarse_get(&start_of_current_tick); + crypto_rand((char*)¤t_tick_num, sizeof(current_tick_num)); + ewma_ticks_initialized = 1; +} + +/** Compute the current cell_ewma tick and the fraction of the tick that has + * elapsed between the start of the tick and the current time. Return the + * former and store the latter in *<b>remainder_out</b>. * * These tick values are not meant to be shared between Tor instances, or used * for other purposes. */ - -static unsigned -cell_ewma_tick_from_timeval(const struct timeval *now, - double *remainder_out) +STATIC unsigned +cell_ewma_get_current_tick_and_fraction(double *remainder_out) { - unsigned res = (unsigned) (now->tv_sec / EWMA_TICK_LEN); - /* rem */ - double rem = (now->tv_sec % EWMA_TICK_LEN) + - ((double)(now->tv_usec)) / 1.0e6; - *remainder_out = rem / EWMA_TICK_LEN; - return res; + if (BUG(!ewma_ticks_initialized)) { + cell_ewma_initialize_ticks(); // LCOV_EXCL_LINE + } + monotime_coarse_t now; + monotime_coarse_get(&now); + // XXXX this does a division operation that can be slow on 32-bit + // XXXX systems. + int32_t msec_diff = + (int32_t)monotime_coarse_diff_msec(&start_of_current_tick, + &now); + if (msec_diff > (1000*EWMA_TICK_LEN)) { + unsigned ticks_difference = msec_diff / (1000*EWMA_TICK_LEN); + monotime_coarse_add_msec(&start_of_current_tick, + &start_of_current_tick, + ticks_difference * 1000 * EWMA_TICK_LEN); + current_tick_num += ticks_difference; + msec_diff %= 1000*EWMA_TICK_LEN; + } + *remainder_out = ((double)msec_diff) / (1.0e3 * EWMA_TICK_LEN); + return current_tick_num; }
/* Default value for the CircuitPriorityHalflifeMsec consensus parameter in @@ -678,6 +704,8 @@ cmux_ewma_set_options(const or_options_t *options, double halflife; const char *source;
+ cell_ewma_initialize_ticks(); + /* Both options and consensus can be NULL. This assures us to either get a * valid configured value or the default one. */ halflife = get_circuit_priority_halflife(options, consensus, &source); @@ -788,3 +816,12 @@ pop_first_cell_ewma(ewma_policy_data_t *pol) offsetof(cell_ewma_t, heap_index)); }
+/** + * Drop all resources held by circuitmux_ewma.c, and deinitialize the + * module. */ +void +circuitmux_ewma_free_all(void) +{ + ewma_ticks_initialized = 0; +} + diff --git a/src/or/circuitmux_ewma.h b/src/or/circuitmux_ewma.h index 2ef8c2586..f0c4c3609 100644 --- a/src/or/circuitmux_ewma.h +++ b/src/or/circuitmux_ewma.h @@ -19,5 +19,12 @@ extern circuitmux_policy_t ewma_policy; void cmux_ewma_set_options(const or_options_t *options, const networkstatus_t *consensus);
+void circuitmux_ewma_free_all(void); + +#ifdef CIRCUITMUX_EWMA_PRIVATE +STATIC unsigned cell_ewma_get_current_tick_and_fraction(double *remainder_out); +STATIC void cell_ewma_initialize_ticks(void); +#endif + #endif /* !defined(TOR_CIRCUITMUX_EWMA_H) */
diff --git a/src/or/main.c b/src/or/main.c index ffe407329..ee6a2459a 100644 --- a/src/or/main.c +++ b/src/or/main.c @@ -59,6 +59,7 @@ #include "circuitbuild.h" #include "circuitlist.h" #include "circuituse.h" +#include "circuitmux_ewma.h" #include "command.h" #include "compress.h" #include "config.h" @@ -3488,6 +3489,7 @@ tor_free_all(int postfork) consdiffmgr_free_all(); hs_free_all(); dos_free_all(); + circuitmux_ewma_free_all(); if (!postfork) { config_free_all(); or_state_free_all(); diff --git a/src/test/test_channel.c b/src/test/test_channel.c index 812ec6c1a..7d5018ef5 100644 --- a/src/test/test_channel.c +++ b/src/test/test_channel.c @@ -544,6 +544,8 @@ test_channel_outbound_cell(void *arg)
(void) arg;
+ cmux_ewma_set_options(NULL,NULL); + /* The channel will be freed so we need to hijack this so the scheduler * doesn't get confused. */ MOCK(scheduler_release_channel, scheduler_release_channel_mock); diff --git a/src/test/test_circuitmux.c b/src/test/test_circuitmux.c index 75b7a0ea4..14c759870 100644 --- a/src/test/test_circuitmux.c +++ b/src/test/test_circuitmux.c @@ -3,6 +3,7 @@
#define TOR_CHANNEL_INTERNAL_ #define CIRCUITMUX_PRIVATE +#define CIRCUITMUX_EWMA_PRIVATE #define RELAY_PRIVATE #include "or.h" #include "channel.h" @@ -79,8 +80,47 @@ test_cmux_destroy_cell_queue(void *arg) tor_free(dc); }
+static void +test_cmux_compute_ticks(void *arg) +{ + const int64_t NS_PER_S = 1000 * 1000 * 1000; + const int64_t START_NS = U64_LITERAL(1217709000)*NS_PER_S; + int64_t now; + double rem; + unsigned tick; + (void)arg; + circuitmux_ewma_free_all(); + monotime_enable_test_mocking(); + + monotime_coarse_set_mock_time_nsec(START_NS); + cell_ewma_initialize_ticks(); + const unsigned tick_zero = cell_ewma_get_current_tick_and_fraction(&rem); + tt_double_op(rem, OP_GT, -1e-9); + tt_double_op(rem, OP_LT, 1e-9); + + /* 1.5 second later and we should still be in the same tick. */ + now = START_NS + NS_PER_S + NS_PER_S/2; + monotime_coarse_set_mock_time_nsec(now); + tick = cell_ewma_get_current_tick_and_fraction(&rem); + tt_uint_op(tick, OP_EQ, tick_zero); + tt_double_op(rem, OP_GT, .149999999); + tt_double_op(rem, OP_LT, .150000001); + + /* 25 second later and we should be in another tick. */ + now = START_NS + NS_PER_S * 25; + monotime_coarse_set_mock_time_nsec(now); + tick = cell_ewma_get_current_tick_and_fraction(&rem); + tt_uint_op(tick, OP_EQ, tick_zero + 2); + tt_double_op(rem, OP_GT, .499999999); + tt_double_op(rem, OP_LT, .500000001); + + done: + ; +} + struct testcase_t circuitmux_tests[] = { { "destroy_cell_queue", test_cmux_destroy_cell_queue, TT_FORK, NULL, NULL }, + { "compute_ticks", test_cmux_compute_ticks, TT_FORK, NULL, NULL }, END_OF_TESTCASES };