Does GNU/Linux counts processes and threads together

Question

I want to limit the number of processes per user on my machine, with "/etc/security/limits.conf" and the nproc value.

I have read here http://kavassalis.com/2011/03/linux-and-the-maximum-number-of-processes-threads that Linux dosen't distinguish between processes and threads?

My current nproc limit per user is 1024, but if this includes also threads it is to low in point of my view. The man-page of limits.conf only mention "process" for nproc and nothing else.

// edit // sample code in C++ with Boost // g++ -o boost_thread boost_thread.cpp -lboost_thread

#include <unistd.h>
#include <iostream>
#include <boost/thread.hpp>
using namespace std;

int counter;

void print_thread(int i) {
    counter++;
    cout << "thread(" << i << ") counter " << counter << "\n";
    sleep(5);
    counter--;
}

int main() {
    int i = 0;
    int max = 1000000;

    while (i < max) {
        boost::thread(print_thread, i);
        i++;
    }

    return 0;
}

test (removed some lines):

$ ulimit -u
1024
$ ./thread 
...
...
...
thread(828) counter 828
thread(829) counter 829
thread(830) counter 830
thread(831) counter 831
thread(832) counter 832
thread(610) counter thread(833833) counter 834

thread(834) counter 835
thread(835) counter 836
thread(836) counter 837
thread(837) counter 838
thread(838) counter 839
thread(839) counter 840
thread(840) counter 841
thread(841) counter 842
thread(842) counter 843
thread(843) counter 844
thread(844) counter 845
thread(845) counter 846
thread(846) counter 847
thread(847) counter 848
terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::thread_resource_error> >'
  what():  boost::thread_resource_error
Aborted (core dumped)

My laptop uses ~130 processes while being idle. So nproc, or Linux in a wider view, doesn't disinguish between processes and threads. Which seem reasonable to me, because threads could also exhausting, not only processes.

Answer 1

ulimit limits number of processes only. Therefore a value set using

ulimit -u 1024

will limit number of proceses.

eg.

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>

void* test(void *ptr){
   return 0;
}



int main()
{
        pthread_t thread[50];
        int i=0;

      for(i=0;i<50;i++){
      if(!pthread_create( &thread[i], NULL,test,NULL))
         printf("%d ",i);

       }


      for(i=0;i<50;i++)
       pthread_join( thread[i], NULL);
       return 0;
}

set ulimit and check

lab@x:/tmp$ ulimit -a
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 20
file size               (blocks, -f) unlimited
pending signals                 (-i) 16382
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) unlimited
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited
lab@x:/tmp$ 
lab@x:/tmp$ 
lab@x:~$ cd /home/x
lab@x:/home/x$ ./thread 
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 lab@x:/home/x$ 
lab@x:/home/x$ 
lab@x:/home/x$ ulimit -u 10
lab@x:/home/x$ 

process limit is set to 10

lab@x:/home/x$ ./thread 
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 lab@x:/home/x$ 
lab@x:/home/x$ 

here 50 threads can be created.