多线程切换最终导致线程创建失败

发布于 2022-08-26 08:45:34 浏览：998 订阅该版

我在测试rt-thread 在龙芯2k上线程切换所需的花销，我的思路是创建1000个线程，所创将的线程都存放在全局静态数组中，线程中的内容是将自身挂起，如果线程被唤醒，将会唤醒下一个线程，然后再第一个和最后一个线程中测算1000个线程所需的时钟，循环测试一个小时，代码如下
```c

#include <rtthread.h>
#include <stdio.h>
#define THREAD_PRIORITY         25
#define THREAD_STACK_SIZE       512
#define THREAD_TIMESLICE        5
#define THREAD_MAX 1000
#define THREAD_TEST_TIME        1000*60*60
static rt_thread_t tid[THREAD_MAX] ;
static rt_tick_t old_tk,new_tk;
static double  max_tk = 0,min_tk = 0,avg_tk = 0;
static void thread1_entry(void *parameter)
{
    rt_uint64_t flag=RT_NULL;
    rt_uint64_t num = (rt_uint64_t)parameter;
    double      spend_tk;

if(num==0){
        rt_kprintf("start supend ---------------------\n");
    }else if(num==THREAD_MAX-1){
        rt_kprintf("end supend ----------------------\n");
    }

flag = rt_thread_suspend(rt_thread_self());
    if(flag!=RT_EOK){
        rt_kprintf("thread%d is suspend failed\n",num);
        
    }

rt_schedule();

if(num==0){
        old_tk = rt_tick_get();
        rt_kprintf("thread start---------------\n");

}else if(num==THREAD_MAX-1){
            new_tk = rt_tick_get();
            rt_kprintf("thread end------------\n");
            
            spend_tk = (1.0*new_tk-old_tk)/THREAD_MAX;
            printf("old time = %d,new time = %d,spend %f ms do change task \n",old_tk,new_tk,spend_tk);
            // rt_kprintf(" old time = %d,new time = %d,spend %f ms do change task \n",old_tk,spend_tk);

if(min_tk==0||min_tk>spend_tk){
                min_tk = spend_tk;
            }

if(max_tk==0||max_tk<spend_tk){
                max_tk = spend_tk;
            }
            avg_tk += spend_tk;

return ;
    }
    
    flag = rt_thread_resume(tid[num+1]);

return ;
}

static int thread_switch_test(void)
{

/* create thread #1 dynamically */
    rt_tick_t old_tk,new_tk;
    rt_uint64_t i;
    rt_uint64_t flag=RT_NULL;

for(i=0;i<THREAD_MAX;i++){
        tid[i] = rt_thread_create("thread",
                                thread1_entry, (void*)i,
                                THREAD_STACK_SIZE*4,
                                THREAD_PRIORITY, THREAD_TIMESLICE);

if (tid[i] == RT_NULL){
                rt_kprintf("create failed\n");
                return ;
            }

flag = rt_thread_startup(tid[i]);

// if(flag == -RT_ERROR){
        //         rt_kprintf("startup thread%d failed \n",i);
        //     }else{
        //         rt_kprintf("startup thread%d suc\n",i);
        //     }
        if(i==0){
            rt_kprintf("start create thread------------------\n");
        }else if(i==THREAD_MAX-1){
            rt_kprintf("end create thread-------------------\n");
        }
        
    }

rt_thread_mdelay(THREAD_MAX*10/2);//等待线程创建并且运行完成

flag = rt_thread_resume(tid[0]);
    if(flag == -RT_ERROR){
        rt_kprintf("resume thread0 failed \n");
    }

}

int thread_switch(void){

rt_uint64_t count = 0,start_time = 0,end_time = 0;
    int i=0;

start_time = rt_tick_get();
    while(1){

thread_switch_test();

rt_thread_delay(3000);//睡眠3秒等待线程跑完

count++;
            
            end_time = rt_tick_get();
            if(end_time-start_time>(THREAD_TEST_TIME)){
                    break;
            }
           
    }
    printf("do change task %ld times, mins_task = %f ms,max_task  = %f ms,avg_task = %f ms \n",count*1000,min_tk,max_tk,avg_tk/count);

// thread_switch_test();
}

/* export the msh command */
MSH_CMD_EXPORT(thread_switch, thread switch);

```

最后再测试的过程中，前十分钟的运行没什么问题，但之后会出现切换线程的时间大幅度的增加，由原来的0.006ms 突然变成 5ms 左右，而且在运行一段时间后，还会线程创建失败，之后我将线程数量改成500就没有出现这样的问题，请各位指点一下是什么原因