Psetlimit(2)              Oct. 1, 1991               Psetlimit(2)



NAME
     Psetlimit - get or set limits on use of system resources

SYNOPSIS
     LONG Psetlimit( WORD lim, LONG value );

DESCRIPTION
     Psetlimit gets or sets a resource limit for a process. Which
     limit  is  affected is governed by the value of lim, as fol-
     lows:
         1: get/set maximum CPU time for process (in milliseconds)
         2: get/set total maximum memory allowed for process
         3: get/set limit on Malloc'd memory for process

     If value is negative, the limit is unchanged; if value is 0,
     the  corresponding  resource  is  unlimited;  otherwise, the
     resource limit is set to value.


     Setting the "maximum memory" limit means the process is  not
     allowed  to  grow bigger than that size overall. Setting the
     "maximum Malloc'ed" limit means that the process  may  allo-
     cate  no  more than that much memory. The difference is that
     the latter limit applies above and beyond the  text+data+bss
     size of the process.


     Using Psetlimit sets the corresponding limit  for  both  the
     process  and  any  children it creates thereafter. Note that
     the limits apply to each process individually;  setting  the
     child  CPU  limit  value  to  1000 and then using fork(2) to
     create three children results in each of those children get-
     ting  a  CPU  limit  value of one second. They do not have a
     collective or sum total limit of one second.


     There is no restriction on increasing a limit.  Any  process
     may  set  any  of  its  limits or its childrens' limits to a
     value greater than  its  current  limit,  or  even  to  zero
     (unlimited).


     Memory limits do not apply during execution of  Pexec;  that
     is, if a process is limited to (say) 256KB of memory, it can
     still exec a child which uses more


     Memory limits are not retroactive: if a process  owns  256KB
     of  memory  and  then  calls Psetlimit to restrict itself to
     128KB, it will not be terminated, but no Malloc  calls  will
     succeed until its size drops below 128KB.




Version 0.9   Last change: MiNT Programmer's Manual             1






Psetlimit(2)              Oct. 1, 1991               Psetlimit(2)



     CPU limits are retroactive, however: if a process  has  used
     three  CPU seconds and calls Psetlimit to restrict itself to
     one second, it will immediately  receive  SIGXCPU  and  ter-
     minate.


RETURNS
     The old limit (0 if there was no limit).


BUGS
     Since the limit applies to the process and its children, you
     can't  limit  a  child to, say, one millisecond of CPU time:
     the parent must necessarily limit itself before creating the
     child, and if it has used more than a millisecond itself, it
     will die with SIGXCPU.  A new set of lim arguments is needed
     that  apply to the caller's future children without applying
     to the caller.


     To alleviate this, the parent must create  a  child  process
     via  Pvfork, and this process (which hasn't consumed any CPU
     time yet) must call Psetlimit and then Pexec to  create  the
     child that is meant to be limited.


SEE ALSO
     Prusage(2)



























Version 0.9   Last change: MiNT Programmer's Manual             2