Other system limits

These limits apply to the entire system:

Processes: A maximum of 4095 active at any time, except on versions of ARM before v6, where the limit is 63 processes.
On ARM platforms, the limit is actually on the number of separate address spaces; you could have more processes if they happen to be sharing an address space because of vfork() , but that's very unusual.
Prefix space (resource-manager attaches, etc.): Limited by memory.
Sessions and process groups: 4095 (since you need at least one process per session or group).
Physical address space: No limits, except those imposed by the hardware; see the documentation for the chip you're using.

These limits apply to each process:

Number of threads: 32767
Number of timers: 32767
Priorities: 0 through 255
Priority 0 is used for the idle thread; by default, priorities of 64 and greater are privileged, so only processes with an effective user ID of 0 (that is, root) can use them. Non-root processes can use priorities from 1 through 63.

You can change the range of privileged priorities with the -P option for procnto . You can append an s or S to this option if you want out-of-range priority requests by default to saturate at the maximum allowed value instead of resulting in an error.
Memory allocation: Because the malloc() implementation uses signed, 32-bit integers to represent the size internally, you can't allocate more than 2 GB in a single allocation. If the size is greater than 2 GB, these functions indicate an error of ENOMEM: