在rt-thread进行多线程切换最终导致线程创建失败请各位指点一下是什么原因

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

#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 ---------------------
");
}else if(num==THREAD_MAX-1){
rt_kprintf("end supend ----------------------
");
}
flag = rt_thread_suspend(rt_thread_self());
if(flag!=RT_EOK){
rt_kprintf("thread%d is suspend failed
",num);
}
rt_schedule();
if(num==0){
old_tk = rt_tick_get();
rt_kprintf("thread start---------------
");
}else if(num==THREAD_MAX-1){
new_tk = rt_tick_get();
rt_kprintf("thread end------------
");
spend_tk = (1.0*new_tk-old_tk)/THREAD_MAX;
printf("old time = %d,new time = %d,spend %f ms do change task 
",old_tk,new_tk,spend_tk);
// rt_kprintf(" old time = %d,new time = %d,spend %f ms do change task 
",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
");
return ;
}
flag = rt_thread_startup(tid[i]);
// if(flag == -RT_ERROR){
//         rt_kprintf("startup thread%d failed 
",i);
//     }else{
//         rt_kprintf("startup thread%d suc
",i);
//     }
if(i==0){
rt_kprintf("start create thread------------------
");
}else if(i==THREAD_MAX-1){
rt_kprintf("end create thread-------------------
");
}
}
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 
");
}
}
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 
",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