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test-ratelim: calculate timers bias (for slow CPUs) to avoid false-positive

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This can be/should be done for regression tests too.

Refs: https://ci.appveyor.com/project/libevent/libevent/builds/28916689/job/kg621aa194a0qbym
Refs: https://github.com/libevent/libevent/pull/917#issuecomment-553811834
v2: EVENT_BASE_FLAG_PRECISE_TIMER
(cherry picked from commit 8a34869984c470fb243fc9587c469b316add2f7e)
This commit is contained in:
Azat Khuzhin 2019-11-17 18:13:51 +03:00
parent ffc528e99f
commit 8ad26d0b11
1 changed files with 83 additions and 0 deletions
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83
test/test-ratelim.c
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@ -50,6 +50,10 @@
#include "event2/listener.h"
#include "event2/thread.h"
#ifndef MIN
#define MIN(a,b) (((a)<(b))?(a):(b))
#endif
static struct evutil_weakrand_state weakrand_state;
static int cfg_verbose = 0;
@ -85,6 +89,18 @@ struct client_state {
};
static const struct timeval *ms100_common=NULL;
/* Timers bias for slow CPUs, affects:
* - cfg_connlimit_tolerance (--check-connlimit)
* - cfg_grouplimit_tolerance (--check-grouplimit)
* - cfg_stddev_tolerance (--check-stddev)
*/
static int timer_bias_events;
static struct timeval timer_bias_start;
double timer_bias_spend;
/* Real cost is less (approximately ~5 usec),
* this macros adjusted to make the bias less */
#define TIMER_MAX_COST_USEC 10
/* info from check_bucket_levels_cb */
static int total_n_bev_checks = 0;
static ev_int64_t total_rbucket_level=0;
@ -244,6 +260,62 @@ group_drain_cb(evutil_socket_t fd, short events, void *arg)
bufferevent_rate_limit_group_decrement_write(ratelim_group, cfg_group_drain);
}
static void
timer_bias_cb(evutil_socket_t fd, short events, void *arg)
{
struct event *event = arg;
struct timeval end;
struct timeval diff;
/** XXX: use rdtsc? (portability issues?) */
evutil_gettimeofday(&end, NULL);
evutil_timersub(&end, &timer_bias_start, &diff);
timer_bias_spend += diff.tv_sec + diff.tv_usec * 1e6;
timer_bias_start = end;
if (++timer_bias_events == 100)
event_del(event);
}
static double
timer_bias_calculate(void)
{
struct event_config *cfg = NULL;
struct event_base *base = NULL;
struct event *timer = NULL;
struct timeval tv = { 0, 1 };
cfg = event_config_new();
if (!cfg)
goto err;
if (event_config_set_flag(cfg, EVENT_BASE_FLAG_PRECISE_TIMER))
goto err;
base = event_base_new_with_config(cfg);
if (!base)
goto err;
timer = event_new(base, -1, EV_PERSIST, timer_bias_cb, event_self_cbarg());
if (!timer || event_add(timer, &tv)) {
goto err;
}
evutil_gettimeofday(&timer_bias_start, NULL);
event_base_dispatch(base);
event_free(timer);
return MIN(timer_bias_spend / 1e6 / timer_bias_events / TIMER_MAX_COST_USEC, 5);
err:
if (cfg)
event_config_free(cfg);
if (timer)
event_free(timer);
if (base)
event_base_free(base);
fprintf(stderr, "Couldn't create event for CPU cycle counter bias\n");
return -1;
}
static int
test_ratelimiting(void)
{
@ -266,6 +338,7 @@ test_ratelimiting(void)
struct event_config *base_cfg;
struct event *periodic_level_check;
struct event *group_drain_event=NULL;
double timer_bias;
memset(&sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
@ -275,6 +348,16 @@ test_ratelimiting(void)
if (0)
event_enable_debug_mode();
timer_bias = timer_bias_calculate();
if (timer_bias > 1) {
fprintf(stderr, "CPU is slow, timers bias is %f\n", timer_bias);
cfg_connlimit_tolerance *= timer_bias;
cfg_grouplimit_tolerance *= timer_bias;
cfg_stddev_tolerance *= timer_bias;
} else {
printf("CPU is fast enough, timers bias is %f\n", timer_bias);
}
base_cfg = event_config_new();
#ifdef _WIN32