datalock(3c) [hpux man page]

datalock(3C)															      datalock(3C)

NAME

       datalock() - lock process into memory after allocating data and stack space

SYNOPSIS

DESCRIPTION

       allocates  at  least  datsiz bytes of data space and stsiz bytes of stack space, then locks the program in memory.  The data space is allo-
       cated by (see malloc(3C)).  After the program is locked, this space is released by (see malloc(3C)), making it  available  for  use.   This
       allows the calling program to use that much space dynamically without receiving the signal.

       The  effective  user  ID  of  the  calling  process  must  be  super-user or be a member of or have an effective group ID of a group having
       PRIV_MLOCK access to use this call (see setprivgrp(2) in getprivgrp(2)).

EXAMPLES

       The following call to allocates 4096 bytes of data space and 2048 bytes of stack space, then locks the process in memory:

RETURN VALUE

       returns -1 if cannot allocate enough memory or if returned an error (see plock(2)).

WARNINGS

       Multiple datalocks cannot be the same as one big one.

       Methods for calculating the required size are not yet well developed.

AUTHOR

       was developed by HP.

SEE ALSO

       getprivgrp(2), plock(2), thread_safety(5).

																      datalock(3C)

CHMEM(1)						      General Commands Manual							  CHMEM(1)

NAME

       chmem - change memory allocation

SYNOPSIS

       chmem [+] [-] [=] amount file

EXAMPLES

       chmem =50000 a.out  # Give a.out 50K of stack space

       chmem -4000 a.out   # Reduce the stack space by 4000 bytes

       chmem +1000 file1   # Increase each stack by 1000 bytes

DESCRIPTION

       When  a	program is loaded into memory, it is allocated enough memory for the text and data+bss segments, plus an area for the stack.  Data
       segment growth using malloc , brk , or sbrk eats up stack space from the low end.  The amount of stack space to allocate is derived from  a
       field  in  the executable program's file header.  If the combined stack and data segment growth exceeds the stack space allocated, the pro-
       gram will be terminated.

       It is therefore important to set the amount of stack space carefully.  If too little is provided, the program may crash.  If  too  much	is
       provided,  memory  will	be  wasted, and fewer programs will be able to fit in memory and run simultaneously.  MINIX does not swap, so that
       when memory is full, subsequent attempts to fork will fail.  The compiler sets the stack space to the largest possible value (for the Intel
       CPUs, 64K - text - data).  For many programs, this value is far too large.  Nonrecursive programs that do not call brk , sbrk , or malloc ,
       and do not have any local arrays usually do not need more than 8K of stack space.

       The chmem command changes the value of the header field that determines the stack allocation, and thus indirectly the total memory required
       to run the program.  The = option sets the stack size to a specific value; the + and - options increment and decrement the current value by
       the indicated amount.  The old and new stack sizes are printed.

SEE ALSO

       install(1), brk(2).

																	  CHMEM(1)