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tests: latency_measure: Update interrupt latency

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Updates the interrupt to thread benchmark tests to address
a number of items.
  1. Updates descriptions to correctly indicate that it is not
     interrupt latency being measured, but the time to leave
     the interrupt and return to a thread.
  2. Repeats the test numerous times instead of just once to
     get an average.
  3. Overhead from obtaining timestamps is now accounted for.
  4. Adds support for returning to a user thread.

Signed-off-by: Peter Mitsis <peter.mitsis@intel.com>
This commit is contained in:
Peter Mitsis 2023-09-11 12:12:48 -04:00 • committed by Carles Cufí
commit 4e7bb482b1
3 changed files with 151 additions and 143 deletions
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186
tests/benchmarks/latency_measure/src/int_to_thread.c
View file

@ -1,6 +1,6 @@
/*
* Copyright (c) 2012-2014 Wind River Systems, Inc.
* Copyright (c) 2017 Intel Corporation.
* Copyright (c) 2017, 2023 Intel Corporation.
*
* SPDX-License-Identifier: Apache-2.0
*/
@ -10,8 +10,16 @@
*
* @brief Measure time from ISR back to interrupted thread
*
* This file contains test that measures time to switch from the interrupt
* handler back to the interrupted thread.
* This file covers three interrupt to threads scenarios:
* 1. ISR returning to the interrupted kernel thread
* 2. ISR returning to a different (kernel) thread
* 3. ISR returning to a different (user) thread
*
* In all three scenarios, the source of the ISR is a software generated
* interrupt originating from a kernel thread. Ideally, these tests would
* also cover the scenarios where the interrupted thread is a user thread.
* However, some implementations of the irq_offload() routine lock interrupts,
* which is not allowed in userspace.
*/
#include <zephyr/kernel.h>
@ -19,39 +27,133 @@
#include <zephyr/irq_offload.h>
static volatile int flag_var;
static timing_t timestamp_start;
static timing_t timestamp_end;
static K_SEM_DEFINE(isr_sem, 0, 1);
/**
* @brief Test ISR used to measure time to return to thread
*
* @brief Test ISR used to measure best case interrupt latency
*
* The interrupt handler gets the second timestamp.
*
* The interrupt handler gets the first timestamp used in the test.
* It then copies the timetsamp into a message queue and returns.
*/
static void latency_test_isr(const void *unused)
static void test_isr(const void *arg)
{
ARG_UNUSED(unused);
flag_var = 1;
struct k_sem *sem = (struct k_sem *)arg;
timestamp_start = timing_counter_get();
if (arg != NULL) {
k_sem_give(sem);
}
timestamp.sample = timing_counter_get();
}
/**
* @brief Measure time to return from interrupt
*
* @brief Interrupt preparation function
*
* Function makes all the test preparations: registers the interrupt handler,
* gets the first timestamp and invokes the software interrupt.
*
* This function is used to measure the time it takes to return from an
* interrupt.
*/
static void make_int(void)
static void int_to_interrupted_thread(uint32_t num_iterations, uint64_t *sum)
{
flag_var = 0;
irq_offload(latency_test_isr, NULL);
timestamp_end = timing_counter_get();
timing_t start;
timing_t finish;
*sum = 0ull;
for (uint32_t i = 0; i < num_iterations; i++) {
irq_offload(test_isr, NULL);
finish = timing_counter_get();
start = timestamp.sample;
*sum += timing_cycles_get(&start, &finish);
}
}
static void start_thread_entry(void *p1, void *p2, void *p3)
{
uint32_t num_iterations = (uint32_t)(uintptr_t)p1;
struct k_sem *sem = p2;
ARG_UNUSED(p3);
uint64_t sum = 0ull;
timing_t start;
timing_t finish;
/* Ensure that <isr_sem> is unavailable */
(void) k_sem_take(sem, K_NO_WAIT);
k_thread_start(&alt_thread);
for (uint32_t i = 0; i < num_iterations; i++) {
/* 1. Wait on an unavailable semaphore */
k_sem_take(sem, K_FOREVER);
/* 3. Obtain the start and finish timestamps */
finish = timing_counter_get();
start = timestamp.sample;
sum += timing_cycles_get(&start, &finish);
}
timestamp.cycles = sum;
}
static void alt_thread_entry(void *p1, void *p2, void *p3)
{
uint32_t num_iterations = (uint32_t)(uintptr_t)p1;
struct k_sem *sem = p2;
ARG_UNUSED(p3);
for (uint32_t i = 0; i < num_iterations; i++) {
/* 2. Trigger the test_isr() to execute */
irq_offload(test_isr, sem);
/*
* ISR expected to have awakened higher priority start_thread
* thereby preempting alt_thread.
*/
}
k_thread_join(&start_thread, K_FOREVER);
}
static void int_to_another_thread(uint32_t num_iterations, uint64_t *sum,
uint32_t options)
{
int priority;
*sum = 0ull;
priority = k_thread_priority_get(k_current_get());
k_thread_create(&start_thread, start_stack,
K_THREAD_STACK_SIZEOF(start_stack),
start_thread_entry,
(void *)(uintptr_t)num_iterations, &isr_sem, NULL,
priority - 2, options, K_FOREVER);
k_thread_create(&alt_thread, alt_stack,
K_THREAD_STACK_SIZEOF(alt_stack),
alt_thread_entry,
(void *)(uintptr_t)num_iterations, &isr_sem, NULL,
priority - 1, 0, K_FOREVER);
#if CONFIG_USERSPACE
if (options != 0) {
k_thread_access_grant(&start_thread, &isr_sem, &alt_thread);
}
#endif
k_thread_start(&start_thread);
k_thread_join(&alt_thread, K_FOREVER);
*sum = timestamp.cycles;
}
/**
@ -60,24 +162,34 @@ static void make_int(void)
*
* @return 0 on success
*/
int int_to_thread(void)
int int_to_thread(uint32_t num_iterations)
{
uint32_t diff;
bool failed = false;
const char *notes = "";
uint64_t sum;
timing_start();
TICK_SYNCH();
make_int();
if (flag_var != 1) {
error_count++;
notes = "Flag variable did not change";
failed = true;
}
diff = timing_cycles_get(&timestamp_start, &timestamp_end);
PRINT_STATS("Switch from ISR back to interrupted thread",
diff, failed, notes);
int_to_interrupted_thread(num_iterations, &sum);
PRINT_STATS_AVG("Switch from ISR back to interrupted thread",
(uint32_t)sum, num_iterations, false, "");
/* ************** */
int_to_another_thread(num_iterations, &sum, 0);
PRINT_STATS_AVG("Switch from ISR to another thread (kernel)",
(uint32_t)sum, num_iterations, false, "");
/* ************** */
#if CONFIG_USERSPACE
int_to_another_thread(num_iterations, &sum, K_USER);
PRINT_STATS_AVG("Switch from ISR to another thread (user)",
(uint32_t)sum, num_iterations, false, "");
#endif
timing_stop();
return 0;
}

101
tests/benchmarks/latency_measure/src/int_to_thread_evt.c
View file

@ -1,101 +0,0 @@
/*
* Copyright (c) 2012-2014 Wind River Systems, Inc.
*
* SPDX-License-Identifier: Apache-2.0
*/
/**
* @file
*
* @brief measure time from ISR to a rescheduled thread
*
* This file contains test that measures time to switch from an interrupt
* handler to executing a thread after rescheduling. In other words, execution
* after interrupt handler resume in a different thread than the one which got
* interrupted.
*/
#include <zephyr/kernel.h>
#include <zephyr/irq_offload.h>
#include "utils.h"
static timing_t timestamp_start;
static timing_t timestamp_end;
static struct k_work work;
K_SEM_DEFINE(INTSEMA, 0, 1);
K_SEM_DEFINE(WORKSEMA, 0, 1);
/**
*
* @brief Test ISR used to measure best case interrupt latency
*
* The interrupt handler gets the second timestamp.
*
*/
static void latency_test_isr(const void *unused)
{
ARG_UNUSED(unused);
k_work_submit(&work);
timestamp_start = timing_counter_get();
}
static void worker(struct k_work *item)
{
(void)item;
timestamp_end = timing_counter_get();
k_sem_give(&WORKSEMA);
}
/**
*
* @brief Software interrupt generating thread
*
* Lower priority thread that, when it starts, it waits for a semaphore. When
* it gets it, released by the main thread, sets up the interrupt handler and
* generates the software interrupt
*
* @return 0 on success
*/
void int_thread(void *p1, void *p2, void *p3)
{
ARG_UNUSED(p1);
ARG_UNUSED(p2);
ARG_UNUSED(p3);
k_sem_take(&INTSEMA, K_FOREVER);
irq_offload(latency_test_isr, NULL);
k_thread_suspend(k_current_get());
}
K_THREAD_DEFINE(int_thread_id, 512, int_thread, NULL, NULL,
NULL, 11, 0, 0);
/**
*
* @brief The test main function
*
* @return 0 on success
*/
int int_to_thread_evt(void)
{
uint32_t diff;
k_work_init(&work, worker);
timing_start();
TICK_SYNCH();
k_sem_give(&INTSEMA);
k_sem_take(&WORKSEMA, K_FOREVER);
timing_stop();
diff = timing_cycles_get(&timestamp_start, &timestamp_end);
PRINT_STATS("Time from ISR to executing a different thread",
diff, false, "");
return 0;
}

7
tests/benchmarks/latency_measure/src/main.c
View file

@ -45,8 +45,7 @@ struct k_thread alt_thread;
int error_count; /* track number of errors */
extern void thread_switch_yield(uint32_t num_iterations, bool is_cooperative);
extern void int_to_thread(void);
extern void int_to_thread_evt(void);
extern void int_to_thread(uint32_t num_iterations);
extern void sema_test_signal(void);
extern void mutex_lock_unlock(void);
extern int sema_context_switch(void);
@ -81,9 +80,7 @@ static void test_thread(void *arg1, void *arg2, void *arg3)
/* Cooperative threads context switching */
thread_switch_yield(NUM_ITERATIONS, true);
int_to_thread();
int_to_thread_evt();
int_to_thread(NUM_ITERATIONS);
suspend_resume();