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[英]iOS: How do you measure the width and height of a string using Quartz?
[英]How do you measure actual on-CPU time for an iOS thread?
我正在寻找Android的SystemClock.currentThreadTimeMillis()或Microsoft的GetThreadTimes()或Posix clock_gettime(CLOCK_THREAD_CPUTIME_ID,)和pthread_getcpuclockid()函数的iOS模拟来测量多线程应用程序中函数使用的实际“干净”时间。 也就是说,我不想测量功能中花费的实际挂钟时间,而是测量CPU上的时间。
我在stackoverflow和其他地方找到了有关这方面的有趣讨论。 不幸的是,它们都不适用于iOS。
在iOS上有这样的功能吗?
万一有人在寻找一个好的答案:
不久之前,我在这个答案中找到了一些很棒的代码(用于在OSX中查找CPU时间/内存使用情况),并稍微调整了一下。 我用它来对ARM上的一些NEON优化进行基准测试。 您可能只需要为当前线程获取时间的部分。
#include <sys/types.h>
#include <sys/sysctl.h>
#include <mach/mach_init.h>
#include <mach/mach_host.h>
#include <mach/mach_port.h>
#include <mach/mach_traps.h>
#include <mach/task_info.h>
#include <mach/thread_info.h>
#include <mach/thread_act.h>
#include <mach/vm_region.h>
#include <mach/vm_map.h>
#include <mach/task.h>
typedef struct {
double utime, stime;
} CPUTime;
int get_cpu_time(CPUTime *rpd, bool_t thread_only)
{
task_t task;
kern_return_t error;
mach_msg_type_number_t count;
thread_array_t thread_table;
thread_basic_info_t thi;
thread_basic_info_data_t thi_data;
unsigned table_size;
struct task_basic_info ti;
if (thread_only) {
// just get time of this thread
count = THREAD_BASIC_INFO_COUNT;
thi = &thi_data;
error = thread_info(mach_thread_self(), THREAD_BASIC_INFO, (thread_info_t)thi, &count);
rpd->utime = thi->user_time.seconds + thi->user_time.microseconds * 1e-6;
rpd->stime = thi->system_time.seconds + thi->system_time.microseconds * 1e-6;
return 0;
}
// get total time of the current process
task = mach_task_self();
count = TASK_BASIC_INFO_COUNT;
error = task_info(task, TASK_BASIC_INFO, (task_info_t)&ti, &count);
assert(error == KERN_SUCCESS);
{ /* calculate CPU times, adapted from top/libtop.c */
unsigned i;
// the following times are for threads which have already terminated and gone away
rpd->utime = ti.user_time.seconds + ti.user_time.microseconds * 1e-6;
rpd->stime = ti.system_time.seconds + ti.system_time.microseconds * 1e-6;
error = task_threads(task, &thread_table, &table_size);
assert(error == KERN_SUCCESS);
thi = &thi_data;
// for each active thread, add up thread time
for (i = 0; i != table_size; ++i) {
count = THREAD_BASIC_INFO_COUNT;
error = thread_info(thread_table[i], THREAD_BASIC_INFO, (thread_info_t)thi, &count);
assert(error == KERN_SUCCESS);
if ((thi->flags & TH_FLAGS_IDLE) == 0) {
rpd->utime += thi->user_time.seconds + thi->user_time.microseconds * 1e-6;
rpd->stime += thi->system_time.seconds + thi->system_time.microseconds * 1e-6;
}
error = mach_port_deallocate(mach_task_self(), thread_table[i]);
assert(error == KERN_SUCCESS);
}
error = vm_deallocate(mach_task_self(), (vm_offset_t)thread_table, table_size * sizeof(thread_array_t));
assert(error == KERN_SUCCESS);
}
if (task != mach_task_self()) {
mach_port_deallocate(mach_task_self(), task);
assert(error == KERN_SUCCESS);
}
return 0;
}
我使用此代码来测量线程CPU时间。 它基于tcovo的答案 ,但更简洁,更专注。
#ifndef thread_time_h
#define thread_time_h
#include <stdint.h>
typedef struct thread_time {
int64_t user_time_us;
int64_t system_time_us;
} thread_time_t;
thread_time_t thread_time();
thread_time_t thread_time_sub(thread_time_t const a, thread_time_t const b);
#endif /* thread_time_h */
#include "thread_time.h"
#include <mach/mach_init.h>
#include <mach/thread_act.h>
#include <mach/thread_info.h>
int64_t time_value_to_us(time_value_t const t) {
return (int64_t)t.seconds * 1000000 + t.microseconds;
}
thread_time_t thread_time() {
thread_basic_info_data_t basic_info;
mach_msg_type_number_t count = THREAD_BASIC_INFO_COUNT;
kern_return_t const result = thread_info(mach_thread_self(), THREAD_BASIC_INFO, (thread_info_t)&basic_info, &count);
if (result == KERN_SUCCESS) {
return (thread_time_t){
.user_time_us = time_value_to_us(basic_info.user_time),
.system_time_us = time_value_to_us(basic_info.system_time)
};
} else {
return (thread_time_t){-1, -1};
}
}
thread_time_t thread_time_sub(thread_time_t const a, thread_time_t const b) {
return (thread_time_t){
.user_time_us = a.user_time_us - b.user_time_us,
.system_time_us = a.system_time_us - b.system_time_us
};
}
从它的描述看来,clock()函数可以满足您的需求吗?
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