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Date: Wed, 20 May 2009 13:16:05 -0700 (PDT)
From: Peter Steele <psteele@maxiscale.com>
To: Dan Nelson <dnelson@allantgroup.com>
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Cc: #freebsd-questions <freebsd-questions@freebsd.org>
Subject: Re: pthread_detach doesn't release memory
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I should have provided a little more detail. Even if I strip my thread function down to nothing more than this: 

void *mythread(void* param) 
{ 
pthread_exit(NULL); 
} 

my application still grows by 128 bytes each time I spawn a thread with this function. There is no explicit memory for me to deallocate, and my understanding was that by using pthread_detach then any temporary structures allocated by the OS would be released when the thread terminates. This doesn't seem to be the case though, so I'm assuming I'm doing something wrong but I do not know what. 

I use the follow simple app to test this behavior: 

int main() 
{ 
getchar(); 
pthread_t thread; 
pthread_create(&thread, NULL, mythread, NULL); 
getchar(); 
printf("done"); 
getchar(); 
} 

When I hit the first getchar, I check the application's size using ps from another terminal window. It shows 12312k. I then allow the application to proceed to the next getchar, and again check its size with ps. It shows 12440k. Finally, I let it proceed to the final getchar, and again ps shows 12440k. Even if I wait a while the size remains at 12440, and if I create additional threads, then each one adds to the application's footprint. 

What am I missing?