Maximum number of processes
If you’re with some Linux background under you belt then probably the first command you would think about is ulimit -a. The same command exists under Solaris
root@root # ulimit -a core file size (blocks, -c) unlimited data seg size (kbytes, -d) unlimited file size (blocks, -f) unlimited open files (-n) 32768 pipe size (512 bytes, -p) 10 stack size (kbytes, -s) 8192 cpu time (seconds, -t) unlimited max user processes (-u) 19995 virtual memory (kbytes, -v) unlimited
But there is a small difference. Whilst under Linux you are free to use it to change the maximum number of processes available to a single user, under Solaris it won’t work complaining:
ulimit: max user processes: cannot modify limit: Invalid argument
So what’s next? Remember that the maximum size of the process table depends on the total amount of physical memory installed in the system. This dependance is reflected in internal variable, called maxusers, and is determined at boot time.
#define MIN_DEFAULT_MAXUSERS 8u
#define MAX_DEFAULT_MAXUSERS 2048u
#define MAX_MAXUSERS 4096u
if (maxusers == 0) {
pgcnt_t physmegs = physmem >> (20 - PAGESHIFT);
pgcnt_t virtmegs = vmem_size(heap_arena, VMEM_FREE) >> 20;
maxusers = MIN(MAX(MIN(physmegs, virtmegs),
MIN_DEFAULT_MAXUSERS), MAX_DEFAULT_MAXUSERS);}
}
It is also used to set two other kernel variables: max_nprocs and maxuprc to describe the maximum number of process systemwide and the maximum number of processes an ordinary user can have respectively.
if (max_nprocs == 0)
max_nprocs = (10 + 16 * maxusers);
if (platform_max_nprocs > 0 && max_nprocs > platform_max_nprocs)
max_nprocs = platform_max_nprocs;
if (max_nprocs > maxpid)
max_nprocs = maxpid;
if (maxuprc == 0)
maxuprc = (max_nprocs - reserved_procs);
To display the current values form the console just run mdb to explorer these variables:
> maxusers/D maxusers: maxusers: 2048 > max_nprocs/D max_nprocs: max_nprocs: 20000 > maxuprc/D maxuprc: maxuprc: 19995
To set the maximum number of processes a non-root user could have just update maxuprc value through either mdb or /etc/system file. Keep in mind that:
- maxuprc must be less than max_nprocs
- If you want to make your settings permanent across the reboots – use /etc/system file.
Whilst what I’ve said here is true both for Solaris 9 and 10 in Solaris 10 using “Resource Management” you could create more refined constrains to define the way a user can run his/her processes.