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esp_timer: lock-free implementation of esp_timer_get_time

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The implementation of esp_timer_get_time used a critical section, which
resulted in a call time of ~1.8us. To make esp_timer_get_time more
useable as a high-resolution time source, this change replaces the lock
with polling. Call time is reduced to ~0.7us.
This commit is contained in:
Ivan Grokhotkov
2017-08-30 08:43:02 +08:00
parent c743bdac88
commit 1af6384349
2 changed files with 76 additions and 9 deletions
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47
components/esp32/test/test_esp_timer.c
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@@ -322,3 +322,50 @@ TEST_CASE("esp_timer for very short intervals", "[esp_timer]")
vSemaphoreDelete(semaphore);
}
TEST_CASE("esp_timer_get_time call takes less than 1us", "[esp_timer]")
{
uint64_t begin = esp_timer_get_time();
volatile uint64_t end;
const int iter_count = 10000;
for (int i = 0; i < iter_count; ++i) {
end = esp_timer_get_time();
}
int ns_per_call = (int) ((end - begin) * 1000 / iter_count);
printf("esp_timer_get_time: %dns per call\n", ns_per_call);
TEST_ASSERT(ns_per_call < 1000);
}
/* This test runs for about 10 minutes and is disabled in CI */
TEST_CASE("esp_timer_get_time returns monotonic values", "[esp_timer][ignore]")
{
void timer_test_task(void* arg) {
uint64_t last = esp_timer_get_time();
const int iter_count = 1000000000;
for (int i = 0; i < iter_count; ++i) {
uint64_t now = esp_timer_get_time();
if (now < last || now - last > 100) {
printf("core_id:%d now: %lld last:%lld\n", xPortGetCoreID(), now, last);
fflush(stdout);
abort();
}
last = now;
}
xSemaphoreGive((SemaphoreHandle_t) arg);
vTaskDelete(NULL);
}
SemaphoreHandle_t done_1 = xSemaphoreCreateBinary();
SemaphoreHandle_t done_2 = xSemaphoreCreateBinary();
xTaskCreatePinnedToCore(&timer_test_task, "t1", 4096, (void*) done_1, 6, NULL, 0);
xTaskCreatePinnedToCore(&timer_test_task, "t2", 4096, (void*) done_2, 6, NULL, 1);
TEST_ASSERT_TRUE( xSemaphoreTake(done_1, portMAX_DELAY) );
TEST_ASSERT_TRUE( xSemaphoreTake(done_2, portMAX_DELAY) );
vSemaphoreDelete(done_1);
vSemaphoreDelete(done_2);
}