| /* nano_ctx_switch.c - measure context switch time between fibers */ |
| |
| /* |
| * Copyright (c) 2012-2014 Wind River Systems, Inc. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| /* |
| * DESCRIPTION |
| * This file contains fiber context switch time measurement. |
| * The task starts two fibers. One fiber waits on a semaphore. The other, |
| * after starting, releases a semaphore which enable the first fiber to run. |
| * Each fiber increases a common global counter and context switch back and |
| * forth by yielding the cpu. When counter reaches the maximal value, fibers |
| * stop and the average time of context switch is displayed. |
| */ |
| |
| #include "timestamp.h" |
| #include "utils.h" |
| |
| #include <arch/cpu.h> |
| |
| /* number of context switches */ |
| #define NCTXSWITCH 10000 |
| #ifndef STACKSIZE |
| #define STACKSIZE 2000 |
| #endif |
| |
| /* stack used by the fibers */ |
| static char __stack fiberOneStack[STACKSIZE]; |
| static char __stack fiberTwoStack[STACKSIZE]; |
| |
| /* semaphore used for fibers synchronization */ |
| static struct nano_sem syncSema; |
| |
| static uint32_t timestamp = 0; |
| |
| /* context switches counter */ |
| static volatile uint32_t ctxSwitchCounter = 0; |
| |
| /* context switch balancer. Incremented by one fiber, decremented by another*/ |
| static volatile int ctxSwitchBalancer = 0; |
| |
| /** |
| * |
| * fiberOne |
| * |
| * Fiber makes all the test preparations: registers the interrupt handler, |
| * gets the first timestamp and invokes the software interrupt. |
| * |
| * @return N/A |
| */ |
| static void fiberOne(void) |
| { |
| nano_fiber_sem_take(&syncSema, TICKS_UNLIMITED); |
| timestamp = TIME_STAMP_DELTA_GET(0); |
| while (ctxSwitchCounter < NCTXSWITCH) { |
| fiber_yield(); |
| ctxSwitchCounter++; |
| ctxSwitchBalancer--; |
| } |
| timestamp = TIME_STAMP_DELTA_GET(timestamp); |
| } |
| |
| /** |
| * |
| * @brief Check the time when it gets executed after the semaphore |
| * |
| * Fiber starts, waits on semaphore. When the interrupt handler releases |
| * the semaphore, fiber measures the time. |
| * |
| * @return 0 on success |
| */ |
| static void fiberTwo(void) |
| { |
| nano_fiber_sem_give(&syncSema); |
| while (ctxSwitchCounter < NCTXSWITCH) { |
| fiber_yield(); |
| ctxSwitchCounter++; |
| ctxSwitchBalancer++; |
| } |
| } |
| |
| /** |
| * |
| * @brief The test main function |
| * |
| * @return 0 on success |
| */ |
| int nanoCtxSwitch(void) |
| { |
| PRINT_FORMAT(" 4- Measure average context switch time between fibers"); |
| nano_sem_init(&syncSema); |
| ctxSwitchCounter = 0; |
| ctxSwitchBalancer = 0; |
| |
| bench_test_start(); |
| task_fiber_start(&fiberOneStack[0], STACKSIZE, |
| (nano_fiber_entry_t) fiberOne, 0, 0, 6, 0); |
| task_fiber_start(&fiberTwoStack[0], STACKSIZE, |
| (nano_fiber_entry_t) fiberTwo, 0, 0, 6, 0); |
| if (ctxSwitchBalancer > 3 || ctxSwitchBalancer < -3) { |
| PRINT_FORMAT(" Balance is %d. FAILED", ctxSwitchBalancer); |
| } else if (bench_test_end() != 0) { |
| errorCount++; |
| PRINT_OVERFLOW_ERROR(); |
| } else { |
| PRINT_FORMAT(" Average context switch time is %lu tcs = %lu nsec", |
| timestamp / ctxSwitchCounter, |
| SYS_CLOCK_HW_CYCLES_TO_NS_AVG(timestamp, ctxSwitchCounter)); |
| } |
| return 0; |
| } |