| /* int_latency_bench.c - interrupt latency benchmark support */ |
| |
| /* |
| * Copyright (c) 2012-2015 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. |
| */ |
| |
| #include "toolchain.h" |
| #include "sections.h" |
| #include <stdint.h> /* uint32_t */ |
| #include <limits.h> /* ULONG_MAX */ |
| #include <misc/printk.h> /* printk */ |
| #include <sys_clock.h> |
| #include <drivers/system_timer.h> |
| |
| #define NB_CACHE_WARMING_DRY_RUN 7 |
| |
| /* |
| * Timestamp corresponding to when interrupt were turned off. |
| * A value of zero indicated interrupt are not currently locked. |
| */ |
| static uint32_t int_locked_timestamp; |
| |
| /* stats tracking the minimum and maximum time when interrupts were locked */ |
| static uint32_t int_locked_latency_min = ULONG_MAX; |
| static uint32_t int_locked_latency_max; |
| |
| /* overhead added to intLock/intUnlock by this latency benchmark */ |
| static uint32_t initial_start_delay; |
| static uint32_t nesting_delay; |
| static uint32_t stop_delay; |
| |
| /* counter tracking intLock/intUnlock calls once interrupt are locked */ |
| static uint32_t int_lock_unlock_nest; |
| |
| /* indicate if the interrupt latency benchamrk is ready to be used */ |
| static uint32_t int_latency_bench_ready; |
| |
| /* min amount of time it takes from HW interrupt generation to 'C' handler */ |
| uint32_t _hw_irq_to_c_handler_latency = ULONG_MAX; |
| |
| /** |
| * |
| * @brief Start tracking time spent with interrupts locked |
| * |
| * calls to lock interrupt can nest, so this routine can be called numerous |
| * times before interrupt are unlocked |
| * |
| * @return N/A |
| * |
| */ |
| void _int_latency_start(void) |
| { |
| /* when interrupts are not already locked, take time stamp */ |
| if (!int_locked_timestamp && int_latency_bench_ready) { |
| int_locked_timestamp = sys_cycle_get_32(); |
| int_lock_unlock_nest = 0; |
| } |
| int_lock_unlock_nest++; |
| } |
| |
| /** |
| * |
| * @brief Stop accumulating time spent for when interrupts are locked |
| * |
| * This is only call once when the interrupt are being reenabled |
| * |
| * @return N/A |
| * |
| */ |
| void _int_latency_stop(void) |
| { |
| uint32_t delta; |
| uint32_t delayOverhead; |
| uint32_t currentTime = sys_cycle_get_32(); |
| |
| /* ensured intLatencyStart() was invoked first */ |
| if (int_locked_timestamp) { |
| /* |
| * time spent with interrupt lock is: |
| * (current time - time when interrupt got disabled first) - |
| * (delay when invoking start + number nested calls to intLock * |
| * time it takes to call intLatencyStart + intLatencyStop) |
| */ |
| delta = (currentTime - int_locked_timestamp); |
| |
| /* |
| * Substract overhead introduce by the int latency benchmark |
| * only if |
| * it is bigger than delta. It can be possible sometimes for |
| * delta to |
| * be smaller than the estimated overhead. |
| */ |
| delayOverhead = |
| (initial_start_delay + |
| ((int_lock_unlock_nest - 1) * nesting_delay) + stop_delay); |
| if (delta >= delayOverhead) |
| delta -= delayOverhead; |
| |
| /* update max */ |
| if (delta > int_locked_latency_max) |
| int_locked_latency_max = delta; |
| |
| /* update min */ |
| if (delta < int_locked_latency_min) |
| int_locked_latency_min = delta; |
| |
| /* interrupts are now enabled, get ready for next interrupt lock |
| */ |
| int_locked_timestamp = 0; |
| } |
| } |
| |
| /** |
| * |
| * @brief Initialize interrupt latency benchmark |
| * |
| * @return N/A |
| * |
| */ |
| void int_latency_init(void) |
| { |
| uint32_t timeToReadTime; |
| uint32_t cacheWarming = NB_CACHE_WARMING_DRY_RUN; |
| |
| int_latency_bench_ready = 1; |
| |
| /* |
| * measuring delay introduced by the interrupt latency benchmark few |
| * times to ensure we get the best possible values. The overhead of |
| * invoking the latency can changes runtime (i.e. cache hit or miss) |
| * but an estimated overhead is used to adjust Max interrupt latency. |
| * The overhead introduced by benchmark is composed of three values: |
| * initial_start_delay, nesting_delay, stop_delay. |
| */ |
| while (cacheWarming) { |
| /* measure how much time it takes to read time */ |
| timeToReadTime = sys_cycle_get_32(); |
| timeToReadTime = sys_cycle_get_32() - timeToReadTime; |
| |
| /* measure time to call intLatencyStart() and intLatencyStop |
| * takes |
| */ |
| initial_start_delay = sys_cycle_get_32(); |
| _int_latency_start(); |
| initial_start_delay = |
| sys_cycle_get_32() - initial_start_delay - timeToReadTime; |
| |
| nesting_delay = sys_cycle_get_32(); |
| _int_latency_start(); |
| nesting_delay = sys_cycle_get_32() - nesting_delay - timeToReadTime; |
| |
| stop_delay = sys_cycle_get_32(); |
| _int_latency_stop(); |
| stop_delay = sys_cycle_get_32() - stop_delay - timeToReadTime; |
| |
| /* re-initialize globals to default values */ |
| int_locked_latency_min = ULONG_MAX; |
| int_locked_latency_max = 0; |
| |
| cacheWarming--; |
| } |
| } |
| |
| /** |
| * |
| * @brief Dumps interrupt latency values |
| * |
| * The interrupt latency value measures |
| * |
| * @return N/A |
| * |
| */ |
| void int_latency_show(void) |
| { |
| uint32_t intHandlerLatency = 0; |
| |
| if (!int_latency_bench_ready) { |
| printk("error: int_latency_init() has not been invoked\n"); |
| return; |
| } |
| |
| if (int_locked_latency_min != ULONG_MAX) { |
| if (_hw_irq_to_c_handler_latency == ULONG_MAX) { |
| intHandlerLatency = 0; |
| printk(" Min latency from hw interrupt up to 'C' int. " |
| "handler: " |
| "not measured\n"); |
| } else { |
| intHandlerLatency = _hw_irq_to_c_handler_latency; |
| printk(" Min latency from hw interrupt up to 'C' int. " |
| "handler:" |
| " %d tcs = %d nsec\n", |
| intHandlerLatency, |
| SYS_CLOCK_HW_CYCLES_TO_NS(intHandlerLatency)); |
| } |
| |
| printk(" Max interrupt latency (includes hw int. to 'C' " |
| "handler):" |
| " %d tcs = %d nsec\n", |
| int_locked_latency_max + intHandlerLatency, |
| SYS_CLOCK_HW_CYCLES_TO_NS(int_locked_latency_max + intHandlerLatency)); |
| |
| printk(" Overhead substracted from Max int. latency:\n" |
| " for int. lock : %d tcs = %d nsec\n" |
| " each time int. lock nest: %d tcs = %d nsec\n" |
| " for int. unlocked : %d tcs = %d nsec\n", |
| initial_start_delay, |
| SYS_CLOCK_HW_CYCLES_TO_NS(initial_start_delay), |
| nesting_delay, |
| SYS_CLOCK_HW_CYCLES_TO_NS(nesting_delay), |
| stop_delay, |
| SYS_CLOCK_HW_CYCLES_TO_NS(stop_delay)); |
| } else { |
| printk("interrupts were not locked and unlocked yet\n"); |
| } |
| /* |
| * Lets start with new values so that one extra long path executed |
| * with interrupt disabled hide smaller paths with interrupt |
| * disabled. |
| */ |
| int_locked_latency_min = ULONG_MAX; |
| int_locked_latency_max = 0; |
| } |