Memory management
Hello,
I have a theoretical question about programs memory. When I'm about o run a program, the Operating system saves memory for it to work. But, this amount already counts the heap and the stack? Or it count only the stack portion and the programmer can use as much heap as the heap as he wants? Thanks!
I have a theoretical question about programs memory. When I'm about o run a program, the Operating system saves memory for it to work. But, this amount already counts the heap and the stack? Or it count only the stack portion and the programmer can use as much heap as the heap as he wants? Thanks!
Well the OS doesn't know in advance what a program is going to need.
In the abstract, both stack and heap are infinite.
In a practical sense, both are physically limited by the nature of running on finite machines.
Also, the limits can be imposed at the OS level, per user or even per process.
So in this case, a process can use up to 8MB of stack, and as much heap as necessary (well until the OS decides it's physically unable to allocate more).
But if you're looking on the various programming contest sites, you may see phrases like "Max 50MB memory, max 1 second of CPU time". These are achieved by the contest admin tweaking the limits for submitted entries.
In the abstract, both stack and heap are infinite.
In a practical sense, both are physically limited by the nature of running on finite machines.
Also, the limits can be imposed at the OS level, per user or even per process.
$ ulimit -a core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited scheduling priority (-e) 0 file size (blocks, -f) unlimited pending signals (-i) 63596 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) 63596 virtual memory (kbytes, -v) unlimited file locks (-x) unlimited |
So in this case, a process can use up to 8MB of stack, and as much heap as necessary (well until the OS decides it's physically unable to allocate more).
But if you're looking on the various programming contest sites, you may see phrases like "Max 50MB memory, max 1 second of CPU time". These are achieved by the contest admin tweaking the limits for submitted entries.
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