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[netbsd-mini2440.git] / sys / uvm / uvm_amap.h

/*      $NetBSD: uvm_amap.h,v 1.33 2007/07/21 19:21:53 ad Exp $ */

/*
 *
 * Copyright (c) 1997 Charles D. Cranor and Washington University.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Charles D. Cranor and
 *      Washington University.
 * 4. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef _UVM_UVM_AMAP_H_
#define _UVM_UVM_AMAP_H_

/*
 * uvm_amap.h: general amap interface and amap implementation-specific info
 */

/*
 * an amap structure contains pointers to a set of anons that are
 * mapped together in virtual memory (an anon is a single page of
 * anonymous virtual memory -- see uvm_anon.h).  in uvm we hide the
 * details of the implementation of amaps behind a general amap
 * interface.  this allows us to change the amap implementation
 * without having to touch the rest of the code.  this file is divided
 * into two parts: the definition of the uvm amap interface and the
 * amap implementation-specific definitions.
 */

#ifdef _KERNEL

/*
 * part 1: amap interface
 */

void    uvm_amap_init(void);

/*
 * forward definition of vm_amap structure.  only amap
 * implementation-specific code should directly access the fields of
 * this structure.
 */

struct vm_amap;


/*
 * prototypes for the amap interface
 */

void            amap_add        /* add an anon to an amap */
                        (struct vm_aref *, vaddr_t,
                         struct vm_anon *, bool);
struct vm_amap  *amap_alloc     /* allocate a new amap */
                        (vaddr_t, vaddr_t, int);
void            amap_copy       /* clear amap needs-copy flag */
                        (struct vm_map *, struct vm_map_entry *, int,
                         vaddr_t, vaddr_t);
void            amap_cow_now    /* resolve all COW faults now */
                        (struct vm_map *, struct vm_map_entry *);
int             amap_extend     /* make amap larger */
                        (struct vm_map_entry *, vsize_t, int);
int             amap_flags      /* get amap's flags */
                        (struct vm_amap *);
void            amap_free       /* free amap */
                        (struct vm_amap *);
void            amap_lock       /* lock amap */
                        (struct vm_amap *);
struct vm_anon  *amap_lookup    /* lookup an anon @ offset in amap */
                        (struct vm_aref *, vaddr_t);
void            amap_lookups    /* lookup multiple anons */
                        (struct vm_aref *, vaddr_t,
                         struct vm_anon **, int);
void            amap_ref        /* add a reference to an amap */
                        (struct vm_amap *, vaddr_t, vsize_t, int);
int             amap_refs       /* get number of references of amap */
                        (struct vm_amap *);
void            amap_share_protect /* protect pages in a shared amap */
                        (struct vm_map_entry *, vm_prot_t);
void            amap_splitref   /* split reference to amap into two */
                        (struct vm_aref *, struct vm_aref *, vaddr_t);
void            amap_unadd      /* remove an anon from an amap */
                        (struct vm_aref *, vaddr_t);
void            amap_unlock     /* unlock amap */
                        (struct vm_amap *);
void            amap_unref      /* drop reference to an amap */
                        (struct vm_amap *, vaddr_t, vsize_t, bool);
void            amap_wipeout    /* remove all anons from amap */
                        (struct vm_amap *);
bool            amap_swap_off
                        (int, int);

/*
 * amap flag values
 */

#define AMAP_SHARED     0x1     /* amap is shared */
#define AMAP_REFALL     0x2     /* amap_ref: reference entire amap */
#define AMAP_SWAPOFF    0x4     /* amap_swap_off() is in progress */

/*
 * amap_copy flags
 */

#define AMAP_COPY_NOWAIT        0x02    /* not allowed to sleep */
#define AMAP_COPY_NOCHUNK       0x04    /* not allowed to chunk */
#define AMAP_COPY_NOMERGE       0x08    /* not allowed to merge */

/*
 * amap_extend flags
 */
#define AMAP_EXTEND_BACKWARDS   0x00    /* add "size" to start of map */
#define AMAP_EXTEND_FORWARDS    0x01    /* add "size" to end of map */
#define AMAP_EXTEND_NOWAIT      0x02    /* not allowed to sleep */

#endif /* _KERNEL */

/**********************************************************************/

/*
 * part 2: amap implementation-specific info
 */

/*
 * we currently provide an array-based amap implementation.  in this
 * implementation we provide the option of tracking split references
 * so that we don't lose track of references during partial unmaps
 * ... this is enabled with the "UVM_AMAP_PPREF" define.
 */

#define UVM_AMAP_PPREF          /* track partial references */

/*
 * here is the definition of the vm_amap structure for this implementation.
 */

struct vm_amap {
        kmutex_t am_l;          /* lock [locks all vm_amap fields] */
        int am_ref;             /* reference count */
        int am_flags;           /* flags */
        int am_maxslot;         /* max # of slots allocated */
        int am_nslot;           /* # of slots currently in map ( <= maxslot) */
        int am_nused;           /* # of slots currently in use */
        int *am_slots;          /* contig array of active slots */
        int *am_bckptr;         /* back pointer array to am_slots */
        struct vm_anon **am_anon; /* array of anonymous pages */
#ifdef UVM_AMAP_PPREF
        int *am_ppref;          /* per page reference count (if !NULL) */
#endif
        LIST_ENTRY(vm_amap) am_list;
};

/*
 * note that am_slots, am_bckptr, and am_anon are arrays.   this allows
 * fast lookup of pages based on their virual address at the expense of
 * some extra memory.   in the future we should be smarter about memory
 * usage and fall back to a non-array based implementation on systems
 * that are short of memory (XXXCDC).
 *
 * the entries in the array are called slots... for example an amap that
 * covers four pages of virtual memory is said to have four slots.   here
 * is an example of the array usage for a four slot amap.   note that only
 * slots one and three have anons assigned to them.  "D/C" means that we
 * "don't care" about the value.
 *
 *            0     1      2     3
 * am_anon:   NULL, anon0, NULL, anon1          (actual pointers to anons)
 * am_bckptr: D/C,  1,     D/C,  0              (points to am_slots entry)
 *
 * am_slots:  3, 1, D/C, D/C                    (says slots 3 and 1 are in use)
 *
 * note that am_bckptr is D/C if the slot in am_anon is set to NULL.
 * to find the entry in am_slots for an anon, look at am_bckptr[slot],
 * thus the entry for slot 3 in am_slots[] is at am_slots[am_bckptr[3]].
 * in general, if am_anon[X] is non-NULL, then the following must be
 * true: am_slots[am_bckptr[X]] == X
 *
 * note that am_slots is always contig-packed.
 */

/*
 * defines for handling of large, sparse amaps:
 *
 * one of the problems of array-based amaps is that if you allocate a
 * large, sparsely-used area of virtual memory you end up allocating
 * large arrays that, for the most part, don't get used.  this is a
 * problem for BSD in that the kernel likes to make these types of
 * allocations to "reserve" memory for possible future use.
 *
 * for example, the kernel allocates (reserves) a large chunk of user
 * VM for possible stack growth.  most of the time only a page or two
 * of this VM is actually used.  since the stack is anonymous memory
 * it makes sense for it to live in an amap, but if we allocated an
 * amap for the entire stack range we could end up wasting a large
 * amount of malloc'd KVM.
 *
 * for example, on the i386 at boot time we allocate two amaps for the stack
 * of /sbin/init:
 *  1. a 7680 slot amap at protection 0 (reserve space for stack)
 *  2. a 512 slot amap at protection 7 (top of stack)
 *
 * most of the array allocated for the amaps for this is never used.
 * the amap interface provides a way for us to avoid this problem by
 * allowing amap_copy() to break larger amaps up into smaller sized
 * chunks (controlled by the "canchunk" option).   we use this feature
 * to reduce our memory usage with the BSD stack management.  if we
 * are asked to create an amap with more than UVM_AMAP_LARGE slots in it,
 * we attempt to break it up into a UVM_AMAP_CHUNK sized amap if the
 * "canchunk" flag is set.
 *
 * so, in the i386 example, the 7680 slot area is never referenced so
 * nothing gets allocated (amap_copy is never called because the protection
 * is zero).   the 512 slot area for the top of the stack is referenced.
 * the chunking code breaks it up into 16 slot chunks (hopefully a single
 * 16 slot chunk is enough to handle the whole stack).
 */

#define UVM_AMAP_LARGE  256     /* # of slots in "large" amap */
#define UVM_AMAP_CHUNK  16      /* # of slots to chunk large amaps in */

#ifdef _KERNEL

/*
 * macros
 */

/* AMAP_B2SLOT: convert byte offset to slot */
#define AMAP_B2SLOT(S,B) {                                              \
        KASSERT(((B) & (PAGE_SIZE - 1)) == 0);                          \
        (S) = (B) >> PAGE_SHIFT;                                        \
}

/*
 * lock/unlock/refs/flags macros
 */

#define amap_flags(AMAP)        ((AMAP)->am_flags)
#define amap_lock(AMAP)         mutex_enter(&(AMAP)->am_l)
#define amap_lock_try(AMAP)     mutex_tryenter(&(AMAP)->am_l)
#define amap_refs(AMAP)         ((AMAP)->am_ref)
#define amap_unlock(AMAP)       mutex_exit(&(AMAP)->am_l)

/*
 * if we enable PPREF, then we have a couple of extra functions that
 * we need to prototype here...
 */

#ifdef UVM_AMAP_PPREF

#define PPREF_NONE ((int *) -1) /* not using ppref */

void            amap_pp_adjref          /* adjust references */
                        (struct vm_amap *, int, vsize_t, int);
void            amap_pp_establish       /* establish ppref */
                        (struct vm_amap *, vaddr_t);
void            amap_wiperange          /* wipe part of an amap */
                        (struct vm_amap *, int, int);
#endif  /* UVM_AMAP_PPREF */

#endif /* _KERNEL */

#endif /* _UVM_UVM_AMAP_H_ */