pthread attributes.

I meant to post more last week, but we had a huge LAN party at WSU a few days ago, thanks to everyone who came and made it awesome :).

Anywho...My next tidbit of information is about pthreads. I had to learn this because when I was writing a piece of software for work, I noticed that I couldn't launch more than about 300 threads before it would start refusing to launch more. After a few hours of research on google I found that it was due to the fact that even though each thread was only using kilobytes of memory, the default thread stack size is somewhere in the range of 1-8mb in most linuxes (it was 8 in the os I was using), which means that even though there was only about 4mb allocated in my program the system was "out of memory" to allocate. But thats ok, we can fix it, we have the technology.

This can all be remedied by changing the thread stack size before we create new pthreads. It is accomplished with this simple bit of code:

size_t size = 0x10000;
pthread_attr_t tattr;

if (pthread_attr_init(&tattr) !=0 )
{fprintf(stderr,"pthread_attr_init() failed\n");}
if (pthread_attr_setstacksize(&tattr,size) !=0 )
{fprintf(stderr,"pthread_attr_stacksize() failed\n");}

pthread_attr_getstacksize(&tattr,&size); /* find out the stacksize */
fprintf(stderr,"Thread stack size: %dKB\n",(int)size/1024);

The last two lines are not needed, but I like to keep them in especially while I am developing this software, to make sure it is working the same way on various computers I try compiling it for. Using that value of size it will have threads with 64KB of stack size.

You can check the defaults of your linux for stack size, open file discriptors, and all the other things you need to make sure of when writing an intensive network app by typing 'ulimit -a'.

But more ulimit things later.

Over and out.

-Crusher4