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UVM(9)

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NAME    [Toc]    [Back]

     uvm - virtual memory system external interface

SYNOPSIS    [Toc]    [Back]

     #include <sys/param.h>
     #include <uvm/uvm.h>

DESCRIPTION    [Toc]    [Back]

     The UVM virtual memory system manages access to the  computer's memory resources.
   User  processes  and  the kernel access these resources through
     UVM's external interface.  UVM's external interface includes
functions
     that:

     -   initialise UVM sub-systems
     -   manage virtual address spaces
     -   resolve page faults
     -   memory map files and devices
     -   perform uio-based I/O to virtual memory
     -   allocate and free kernel virtual memory
     -   allocate and free physical memory

     In addition to exporting these services, UVM has two kernellevel processes:
 pagedaemon  and  swapper.   The  pagedaemon  process
sleeps until
     physical memory becomes scarce.  When that happens, pagedaemon is awoken.
     It scans physical memory, paging out and freeing memory that
has not been
     recently  used.   The swapper process swaps in runnable processes that are
     currently swapped out, if there is room.

     There are also several miscellaneous functions.

INITIALISATION    [Toc]    [Back]

     void
     uvm_init(void);

     void
     uvm_init_limits(struct proc *p);

     void
     uvm_setpagesize(void);

     void
     uvm_swap_init(void);

     The uvm_init() function sets up the  UVM  system  at  system
boot time, after
     the  copyright  has  been  printed.   It  initialises global
state, the page,
     map, kernel virtual memory state, machine-dependent physical
map, kernel
     memory  allocator,  pager  and anonymous memory sub-systems,
and then enables
 paging of kernel objects.  uvm_init() must  be  called
after machinedependent
  code  has  registered  some  free  RAM  with  the
uvm_page_physload()
     function.

     The uvm_init_limits() function  initialises  process  limits
for the named
     process.   This is for use by the system startup for process
zero, before
     any other processes are created.

     The uvm_setpagesize() function initialises the  uvmexp  members pagesize
     (if  not  already done by machine-dependent code), pageshift
and pagemask.
     It should be called by machine-dependent code early  in  the
pmap_init(9)
     call.

     The  uvm_swap_init()  function initialises the swap sub-system.

VIRTUAL ADDRESS SPACE MANAGEMENT    [Toc]    [Back]

     int
     uvm_map(vm_map_t map, vaddr_t *startp, vsize_t size,
             struct uvm_object  *uobj,  voff_t  uoffset,  vsize_t
alignment,
             uvm_flag_t flags);

     int
     uvm_map_pageable(vm_map_t map, vaddr_t start, vaddr_t end,
             boolean_t new_pageable, int lockflags);

     int
     uvm_map_pageable_all(vm_map_t   map,   int   flags,  vsize_t
limit);

     boolean_t
     uvm_map_checkprot(vm_map_t map, vaddr_t start, vaddr_t end,
             vm_prot_t protection);

     int
     uvm_map_protect(vm_map_t map, vaddr_t start, vaddr_t end,
             vm_prot_t new_prot, boolean_t set_max);

     int
     uvm_deallocate(vm_map_t map, vaddr_t start, vsize_t size);

     struct vmspace *
     uvmspace_alloc(vaddr_t min, vaddr_t max, int pageable);

     void
     uvmspace_exec(struct proc *p, vaddr_t start, vaddr_t end);

     struct vmspace *
     uvmspace_fork(struct vmspace *vm);

     void
     uvmspace_free(struct vmspace *vm1);

     void
     uvmspace_share(struct proc *p1, struct proc *p2);

     void
     uvmspace_unshare(struct proc *p);

     int
     UVM_MAPFLAG(vm_prot_t prot, vm_prot_t maxprot,  vm_inherit_t
inh,
             int advice, int flags);

     The  uvm_map()  function  establishes a valid mapping in map
map, which must
     be unlocked.  The new mapping has size size, which  must  be
in PAGE_SIZE
     units.   If alignment is non-zero, it describes the required
alignment of
     the list, in power-of-two notation.  The  uobj  and  uoffset
arguments can
     have  four  meanings.   When  uobj  is  NULL  and uoffset is
UVM_UNKNOWN_OFFSET,
     uvm_map() does not  use  the  machine-dependent  PMAP_PREFER
function.  If
     uoffset  is  any  other  value,  it  is  used as the hint to
PMAP_PREFER.  When
     uobj  is  not  NULL  and  uoffset   is   UVM_UNKNOWN_OFFSET,
uvm_map() finds the
     offset based upon the virtual address, passed as startp.  If
uoffset is
     any other value, we are doing a normal mapping at this  offset.  The start
     address of the map will be returned in startp.

     flags  passed  to  uvm_map() are typically created using the
UVM_MAPFLAG()
     macro, which  uses  the  following  values.   The  prot  and
maxprot can take
     the following values:

     #define UVM_PROT_MASK   0x07    /* protection mask */
     #define UVM_PROT_NONE   0x00    /* protection none */
     #define UVM_PROT_ALL    0x07    /* everything */
     #define UVM_PROT_READ   0x01    /* read */
     #define UVM_PROT_WRITE  0x02    /* write */
     #define UVM_PROT_EXEC   0x04    /* exec */
     #define UVM_PROT_R      0x01    /* read */
     #define UVM_PROT_W      0x02    /* write */
     #define UVM_PROT_RW     0x03    /* read-write */
     #define UVM_PROT_X      0x04    /* exec */
     #define UVM_PROT_RX     0x05    /* read-exec */
     #define UVM_PROT_WX     0x06    /* write-exec */
     #define UVM_PROT_RWX    0x07    /* read-write-exec */

     The values that inh can take are:

     #define UVM_INH_MASK    0x30    /* inherit mask */
     #define UVM_INH_SHARE   0x00    /* "share" */
     #define UVM_INH_COPY    0x10    /* "copy" */
     #define UVM_INH_NONE    0x20    /* "none" */
     #define UVM_INH_DONATE  0x30    /* "donate" << not used */

     The values that advice can take are:

     #define UVM_ADV_NORMAL  0x0     /* 'normal' */
     #define UVM_ADV_RANDOM  0x1     /* 'random' */
     #define UVM_ADV_SEQUENTIAL 0x2  /* 'sequential' */
     #define UVM_ADV_MASK    0x7     /* mask */

     The values that flags can take are:

     #define UVM_FLAG_FIXED   0x010000 /* find space */
     #define UVM_FLAG_OVERLAY 0x020000 /* establish overlay */
     #define UVM_FLAG_NOMERGE 0x040000 /* don't merge map entries
*/
     #define UVM_FLAG_COPYONW 0x080000 /* set copy_on_write  flag
*/
     #define UVM_FLAG_AMAPPAD 0x100000 /* bss: pad amap to reduce
malloc() */
     #define UVM_FLAG_TRYLOCK 0x200000 /* fail if we can not lock
map */

     The  UVM_MAPFLAG  macro arguments can be combined with an or
operator.
     There are several special purpose macros for  checking  protection combinations,
 e.g., the UVM_PROT_WX macro.  There are also some additional
     macros to extract bits from the flags.  The  UVM_PROTECTION,
UVM_INHERIT,
     UVM_MAXPROTECTION  and  UVM_ADVICE macros return the protection, inheritance,
  maximum   protection   and   advice,   respectively.
uvm_map() returns a
     standard UVM return value.

     The  uvm_map_pageable()  function changes the pageability of
the pages in
     the range from start to end in map map to new_pageable.  The
     uvm_map_pageable_all()  function  changes the pageability of
all mapped regions.
  If limit is non-zero and pmap_wired_count()  is  implemented,
     KERN_NO_SPACE  is  returned if the amount of wired pages exceed limit.  The
     map is locked on entry if  lockflags  contain  UVM_LK_ENTER,
and locked on
     exit  if  lockflags contain UVM_LK_EXIT.  uvm_map_pageable()
and
     uvm_map_pageable_all() return a standard UVM return value.

     The uvm_map_checkprot() function checks  the  protection  of
the range from
     start  to  end  in map map against protection.  This returns
either TRUE or
     FALSE.

     The uvm_map_protect() function changes the protection  start
to end in map
     map  to new_prot, also setting the maximum protection to the
region to
     new_prot if set_max is non-zero.  This  function  returns  a
standard UVM
     return value.

     The  uvm_deallocate()  function deallocates kernel memory in
map map from
     address start to start + size.

     The uvmspace_alloc() function allocates and  returns  a  new
address space,
     with  ranges from min to max, setting the pageability of the
address space
     to pageable.

     The uvmspace_exec() function either reuses the address space
of process p
     if there are no other references to it, or creates a new one
with
     uvmspace_alloc().  The range of valid addresses in  the  address space is
     reset to start through end.

     The  uvmspace_fork()  function creates and returns a new address space
     based upon the vm1 address space, typically used when  allocating an address
 space for a child process.

     The  uvmspace_free()  function lowers the reference count on
the address
     space vm, freeing the data structures if there are no  other
references.

     The uvmspace_share() function causes process p2 to share the
address
     space of p1.

     The uvmspace_unshare() function ensures that process  p  has
its own, unshared
  address space, by creating a new one if necessary by
calling
     uvmspace_fork().

PAGE FAULT HANDLING    [Toc]    [Back]

     int
     uvm_fault(vm_map_t  orig_map,  vaddr_t   vaddr,   vm_fault_t
fault_type,
             vm_prot_t access_type);

     The uvm_fault() function is the main entry point for faults.
It takes
     orig_map as the map the fault originated in, a vaddr  offset
into the map
     the fault occurred, fault_type describing the type of fault,
and
     access_type  describing  the  type  of   access   requested.
uvm_fault() returns
     a standard UVM return value.

MEMORY MAPPING FILES AND DEVICES    [Toc]    [Back]

     struct uvm_object *
     uvn_attach(void *arg, vm_prot_t accessprot);

     void
     uvm_vnp_setsize(struct vnode *vp, voff_t newsize);

     void
     uvm_vnp_sync(struct mount *mp);

     void
     uvm_vnp_terminate(struct vnode *vp);

     boolean_t
     uvm_vnp_uncache(struct vnode *vp);

     The  uvn_attach()  function  attaches  a UVM object to vnode
arg, creating
     the object if necessary.  The object is returned.

     The uvm_vnp_setsize() function sets the size of vnode vp  to
newsize.
     Caller  must  hold  a  reference to the vnode.  If the vnode
shrinks, pages
     no longer used are discarded.  This function will be removed
when the
     file system and VM buffer caches are merged.

     The uvm_vnp_sync() function flushes dirty vnodes from either
the mount
     point passed in mp, or all dirty vnodes if mp is NULL.  This
function
     will  be  removed  when the file system and VM buffer caches
are merged.

     The uvm_vnp_terminate() function frees all VM resources  allocated to vnode
  vp.   If the vnode still has references, it will not be
destroyed;
     however all future operations using this  vnode  will  fail.
This function
     will  be  removed  when the file system and VM buffer caches
are merged.

     The uvm_vnp_uncache() function disables vnode vp  from  persisting when all
     references  are  freed.   This function will be removed when
the file-system
     and UVM caches are unified.  Returns true if there is no active vnode.

VIRTUAL MEMORY I/O
     int
     uvm_io(vm_map_t map, struct uio *uio);

     The  uvm_io()  function performs the I/O described in uio on
the memory described
 in map.

ALLOCATION OF KERNEL MEMORY    [Toc]    [Back]

     vaddr_t
     uvm_km_alloc(vm_map_t map, vsize_t size);

     vaddr_t
     uvm_km_zalloc(vm_map_t map, vsize_t size);

     vaddr_t
     uvm_km_alloc1(vm_map_t map, vsize_t size, boolean_t zeroit);

     vaddr_t
     uvm_km_kmemalloc(vm_map_t   map,   struct  uvm_object  *obj,
vsize_t size,
             int flags);

     vaddr_t
     uvm_km_valloc(vm_map_t map, vsize_t size);

     vaddr_t
     uvm_km_valloc_wait(vm_map_t map, vsize_t size);

     struct vm_map *
     uvm_km_suballoc(vm_map_t map, vaddr_t  *min,  vaddr_t  *max,
vsize_t size,
             int flags, boolean_t fixed, vm_map_t submap);

     void
     uvm_km_free(vm_map_t map, vaddr_t addr, vsize_t size);

     void
     uvm_km_free_wakeup(vm_map_t   map,   vaddr_t  addr,  vsize_t
size);

     The uvm_km_alloc() and  uvm_km_zalloc()  functions  allocate
size bytes of
     wired kernel memory in map map.  In addition to allocation,
     uvm_km_zalloc()  zeros  the memory.  Both of these functions
are defined as
     macros in terms of uvm_km_alloc1(), and should almost always
be used in
     preference to uvm_km_alloc1().

     The  uvm_km_alloc1()  function  allocates  and  returns size
bytes of wired
     memory in the kernel map, zeroing the memory if  the  zeroit
argument is
     non-zero.

     The  uvm_km_kmemalloc()  function allocates and returns size
bytes of wired
     kernel memory into obj.  The flags can be any of:

     #define UVM_KMF_NOWAIT  0x1                      /*  matches
M_NOWAIT */
     #define  UVM_KMF_VALLOC  0x2                     /* allocate
VA only */
     #define UVM_KMF_TRYLOCK UVM_FLAG_TRYLOCK        /* try locking only */

     The  UVM_KMF_NOWAIT flag causes uvm_km_kmemalloc() to return
immediately
     if no memory is available.  UVM_KMF_VALLOC causes  no  pages
to be allocated,
   only   a   virtual  address.   UVM_KMF_TRYLOCK  causes
uvm_km_kmemalloc() to
     use simple_lock_try() when locking maps.

     The uvm_km_valloc() and uvm_km_valloc_wait()  functions  return a newly allocated
  zero-filled address in the kernel map of size size.
     uvm_km_valloc_wait() will also wait for kernel memory to become available,
 if there is a memory shortage.

     The  uvm_km_suballoc()  function  allocates submap (with the
specified
     flags, as described above) from map, creating a new  map  if
submap is
     NULL.   The addresses of the submap can be specified exactly
by setting
     the fixed argument to non-zero, which causes the  min  argument to specify
     the beginning of the address in the submap.  If fixed is zero, any address
 of size size will be allocated from map and the  start
and end addresses
 returned in min and max.

     The  uvm_km_free()  and  uvm_km_free_wakeup() functions free
size bytes of
     memory  in  the  kernel  map,  starting  at  address   addr.
uvm_km_free_wakeup()
     calls thread_wakeup() on the map before unlocking the map.

ALLOCATION OF PHYSICAL MEMORY    [Toc]    [Back]

     struct vm_page *
     uvm_pagealloc(struct  uvm_object  *uobj,  voff_t off, struct
vm_anon *anon,
             int flags);

     void
     uvm_pagerealloc(struct  vm_page   *pg,   struct   uvm_object
*newobj,
             voff_t newoff);

     void
     uvm_pagefree(struct vm_page *pg);

     int
     uvm_pglistalloc(psize_t size, paddr_t low, paddr_t high,
             paddr_t  alignment,  paddr_t boundary, struct pglist
*rlist,
             int nsegs, int waitok);

     void
     uvm_pglistfree(struct pglist *list);

     void
     uvm_page_physload(vaddr_t  start,   vaddr_t   end,   vaddr_t
avail_start,
             vaddr_t avail_end, int free_list);

     The  uvm_pagealloc()  function allocates a page of memory at
virtual address
 off in either the object uobj or the anonymous  memory
anon, which
     must  be locked by the caller.  Only one of off and uobj can
be non NULL.
     The flags can be any of:

     #define UVM_PGA_USERESERVE      0x0001  /* ok to use reserve
pages */
     #define  UVM_PGA_ZERO             0x0002   /*  returned page
must be zeroed */

     The UVM_PGA_USERESERVE flag means to allocate a page even if
that will
     result in the number of free pages being lower than
     uvmexp.reserve_pagedaemon  (if  the  current  thread  is the
pagedaemon) or
     uvmexp.reserve_kernel (if the  current  thread  is  not  the
pagedaemon).  The
     UVM_PGA_ZERO flag causes the returned page to be filled with
zeroes, either
 by allocating it from a pool of pre-zeroed pages or  by
zeroing it
     in-line as necessary.

     The  uvm_pagerealloc() function reallocates page pg to a new
object
     newobj, at a new offset newoff, and  returns  NULL  when  no
page can be
     found.

     The uvm_pagefree() function frees the physical page pg.

     The uvm_pglistalloc() function allocates a list of pages for
size size
     byte under various constraints.  low and high  describe  the
lowest and
     highest  addresses acceptable for the list.  If alignment is
non-zero, it
     describes the required alignment of the list,  in  power-oftwo notation.
     If  boundary  is  non-zero, no segment of the list may cross
this power-oftwo
 boundary, relative to zero.  The nsegs and waitok  arguments are currently
 ignored.

     The uvm_pglistfree() function frees the list of pages pointed to by list.

     The uvm_page_physload() function loads physical memory  segments into VM
     space  on the specified free_list.  uvm_page_physload() must
be called at
     system boot time to set up physical memory management pages.
The arguments
  describe  the start and end of the physical addresses
of the segment,
 and the available start and end addresses of pages not
already in
     use.

PROCESSES    [Toc]    [Back]

     void
     uvm_pageout(void *arg);

     void
     uvm_scheduler(void);

     void
     uvm_swapin(struct proc *p);

     The  uvm_pageout()  function  is  the main loop for the page
daemon.  The arg
     argument is ignored.

     The uvm_scheduler() function is the process zero main  loop,
which is to
     be  called after the system has finished starting other processes.
     uvm_scheduler() handles the swapping in of runnable, swapped
out processes
 in priority order.

     The uvm_swapin() function swaps in the named process.

MISCELLANEOUS FUNCTIONS    [Toc]    [Back]

     struct uvm_object *
     uao_create(vsize_t size, int flags);

     void
     uao_detach(struct uvm_object *uobj);

     void
     uao_reference(struct uvm_object *uobj);

     boolean_t
     uvm_chgkprot(caddr_t addr, size_t len, int rw);

     void
     uvm_kernacc(caddr_t addr, size_t len, int rw);

     void
     uvm_vslock(struct proc *p, caddr_t addr, size_t len,
             vm_prot_t access_type);

     void
     uvm_vsunlock(struct proc *p, caddr_t addr, size_t len);

     void
     uvm_meter();

     int
     uvm_sysctl(int  *name,  u_int  namelen,  void  *oldp, size_t
*oldlenp,
             void *newp, size_t newlen, struct proc *p);

     void
     uvm_fork(struct proc *p1, struct proc *p2, boolean_t shared,
void *stack,
             size_t  stacksize,  void  (*func)(void *arg), , void
*arg);

     int
     uvm_grow(struct proc *p, vaddr_t sp);

     int
     uvm_coredump(struct proc *p, struct vnode *vp, struct  ucred
*cred,
             struct core *chdr);

     The uao_create(), uao_detach() and uao_reference() functions
operate on
     anonymous memory objects, such as those used to support System V shared
     memory.   uao_create()  returns  an object of size size with
flags:

     #define UAO_FLAG_KERNOBJ        0x1     /* create kernel object */
     #define  UAO_FLAG_KERNSWAP        0x2      /*  enable kernel
swap */

     which can only be  used  once  each  at  system  boot  time.
uao_reference()
     creates an additional reference to the named anonymous memory object.
     uao_detach() removes a reference from  the  named  anonymous
memory object,
     destroying it if removing the last reference.

     The uvm_chgkprot() function changes the protection of kernel
memory from
     addr to addr + len to the value of rw.   This  is  primarily
useful for debuggers,
  for  setting  breakpoints.   This function is only
available with
     options KGDB.

     The uvm_kernacc() function checks the access at address addr
to addr +
     len for rw access, in the kernel address space.

     The  uvm_vslock()  and  uvm_vsunlock() functions control the
wiring and unwiring
 of pages for process p from addr to addr + len.   The
access_type
     argument  of  uvm_vslock()  is passed to uvm_fault().  These
functions are
     normally used to wire memory for I/O.

     The uvm_meter() function calculates  the  load  average  and
wakes up the
     swapper if necessary.

     The  uvm_sysctl()  function  provides support for the CTL_VM
domain of the
     sysctl(3) hierarchy.  uvm_sysctl() handles  the  VM_LOADAVG,
VM_METER and
     VM_UVMEXP  calls,  which  return  the current load averages,
calculates current
 VM totals, and returns the uvmexp structure respectively.  The load
     averages  are accessed from userland using the getloadavg(3)
function.
     The uvmexp structure has all global state of the UVM system,
and has the
     following members:

     /* vm_page constants */
     int pagesize;   /* size of a page (PAGE_SIZE): must be power
of 2 */
     int pagemask;   /* page mask */
     int pageshift;  /* page shift */

     /* vm_page counters */
     int npages;     /* number of pages we manage */
     int free;       /* number of free pages */
     int active;     /* number of active pages */
     int inactive;   /* number of pages that we  free'd  but  may
want back */
     int  paging;      /* number of pages in the process of being
paged out */
     int wired;      /* number of wired pages */
     int reserve_pagedaemon; /*  number  of  pages  reserved  for
pagedaemon */
     int  reserve_kernel;  /* number of pages reserved for kernel
*/

     /* pageout params */
     int freemin;    /* min number of free pages */
     int freetarg;   /* target number of free pages */
     int inactarg;   /* target number of inactive pages */
     int wiredmax;   /* max number of wired pages */

     /* swap */
     int nswapdev;   /* number of configured swap devices in system */
     int swpages;    /* number of PAGE_SIZE'ed swap pages */
     int swpginuse;  /* number of swap pages in use */
     int   nswget;       /*   number   of   times   fault   calls
uvm_swap_get() */
     int nanon;      /* number total of anons in system */
     int nfreeanon;  /* number of free anons */

     /* stat counters */
     int faults;             /* page fault count */
     int traps;              /* trap count */
     int intrs;              /* interrupt count */
     int swtch;              /* context switch count */
     int softs;              /* software interrupt count */
     int syscalls;           /* system calls */
     int pageins;            /* pagein operation count */
                             /* pageouts are in pdpageouts  below
*/
     int swapins;            /* swapins */
     int swapouts;           /* swapouts */
     int pgswapin;           /* pages swapped in */
     int pgswapout;          /* pages swapped out */
     int forks;              /* forks */
     int forks_ppwait;       /* forks where parent waits */
     int forks_sharevm;      /* forks where vmspace is shared */

     /* fault subcounters */
     int fltnoram;   /* number of times fault was out of ram */
     int fltnoanon;  /* number of times fault was out of anons */
     int fltpgwait;  /* number of times fault had to  wait  on  a
page */
     int  fltpgrele;   /*  number of times fault found a released
page */
     int fltrelck;   /* number of times fault relock called */
     int fltrelckok; /* number of times fault relock is a success
*/
     int fltanget;   /* number of times fault gets anon page */
     int  fltanretry; /* number of times fault retrys an anon get
*/
     int fltamcopy;  /* number of times fault clears "needs copy"
*/
     int  fltnamap;    /*  number  of times fault maps a neighbor
anon page */
     int fltnomap;   /* number of times fault maps a neighbor obj
page */
     int  fltlget;     /*  number  of  times  fault does a locked
pgo_get */
     int fltget;     /* number of times fault  does  an  unlocked
get */
     int flt_anon;   /* number of times fault anon (case 1a) */
     int  flt_acow;   /* number of times fault anon cow (case 1b)
*/
     int flt_obj;    /* number of times fault is on  object  page
(2a) */
     int  flt_prcopy; /* number of times fault promotes with copy
(2b) */
     int flt_przero; /* number of times fault promotes with zerofill (2b) */

     /* daemon counters */
     int pdwoke;     /* number of times daemon woke up */
     int  pdrevs;      /* number of times daemon rev'd clock hand
*/
     int pdswout;    /* number of times daemon called for swapout
*/
     int  pdfreed;     /* number of pages daemon freed since boot
*/
     int pdscans;    /* number of pages daemon scanned since boot
*/
     int pdanscan;   /* number of anonymous pages scanned by daemon */
     int pdobscan;   /* number of object pages scanned by  daemon
*/
     int  pdreact;    /* number of pages daemon reactivated since
boot */
     int pdbusy;     /* number of times daemon found a busy  page
*/
     int  pdpageouts; /* number of times daemon started a pageout
*/
     int pdpending;  /* number of  times  daemon  got  a  pending
pagout */
     int pddeact;    /* number of pages daemon deactivates */

     The  uvm_fork()  function  forks a virtual address space for
process' (old)
     p1 and (new) p2.  If the shared argument  is  non  zero,  p1
shares its address
 space with p2, otherwise a new address space is created.  The
     stack, stacksize, func and arg arguments are passed  to  the
machine-dependent
 cpu_fork() function.  The uvm_fork() function currently
has no return
 value, and thus cannot fail.

     The uvm_grow() function increases the stack segment of  process p to include
 sp.

     The uvm_coredump() function generates a coredump on vnode vp
for process
     p with credentials cred and core header description in chdr.

STANDARD UVM RETURN VALUES    [Toc]    [Back]

     This  section  documents  the  standard  return  values that
callers of UVM
     functions can expect.  They are derived  from  the  Mach  VM
values of the
     same function.  The full list of values can be seen below.

     #define KERN_SUCCESS            0
     #define KERN_INVALID_ADDRESS    1
     #define KERN_PROTECTION_FAILURE 2
     #define KERN_NO_SPACE           3
     #define KERN_INVALID_ARGUMENT   4
     #define KERN_FAILURE            5
     #define KERN_RESOURCE_SHORTAGE  6
     #define KERN_NOT_RECEIVER       7
     #define KERN_NO_ACCESS          8
     #define KERN_PAGES_LOCKED       9

     Note that KERN_NOT_RECEIVER and KERN_PAGES_LOCKED values are
not actually
     returned by the UVM code.

NOTES    [Toc]    [Back]

     The structure and types whose names begin with ``vm_''  were
named so UVM
     could  coexist  with  BSD  VM  during  the early development
stages.  They will
     be renamed to ``uvm_''.

SEE ALSO    [Toc]    [Back]

      
      
     getloadavg(3),  kvm(3),   sysctl(3),   ddb(4),   options(4),
pmap(9)

HISTORY    [Toc]    [Back]

     UVM is a new VM system developed at Washington University in
St. Louis
     (Missouri).  UVM's roots lie partly in the Mach-based 4.4BSD
VM system,
     the  FreeBSD VM system, and the SunOS4 VM system.  UVM's basic structure
     is based on the 4.4BSD VM system.  UVM's new anonymous memory system is
     based  on the anonymous memory system found in the SunOS4 VM
(as described
     in papers published by Sun Microsystems,  Inc.).   UVM  also
includes a number
 of features new to BSD including page loanout, map entry
passing,
     simplified copy-on-write, and clustered anonymous memory pageout.  UVM is
     also  further  documented  in an August 1998 dissertation by
Charles D. Cranor.


     UVM appeared in OpenBSD 2.9.

AUTHORS    [Toc]    [Back]

     Charles D. Cranor <chuck@ccrc.wustl.edu> designed and implemented UVM.

     Matthew  Green <mrg@eterna.com.au> wrote the swap-space management code.

     Chuck Silvers <chuq@chuq.com> implemented  the  aobj  pager,
thus allowing
     UVM  to support System V shared memory and process swapping.

     Artur Grabowski <art@openbsd.org> handled the logistical issues involved
     with merging UVM into the OpenBSD source tree.

BUGS    [Toc]    [Back]

     The uvm_fork() function should be able to fail in low memory
conditions.

OpenBSD     3.6                          March      26,      2000
[ Back ]
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