Annotation of sys/uvm/uvm_amap.h, Revision 1.1.1.1
1.1 nbrk 1: /* $OpenBSD: uvm_amap.h,v 1.17 2007/06/18 21:51:15 pedro Exp $ */
2: /* $NetBSD: uvm_amap.h,v 1.14 2001/02/18 21:19:08 chs Exp $ */
3:
4: /*
5: *
6: * Copyright (c) 1997 Charles D. Cranor and Washington University.
7: * All rights reserved.
8: *
9: * Redistribution and use in source and binary forms, with or without
10: * modification, are permitted provided that the following conditions
11: * are met:
12: * 1. Redistributions of source code must retain the above copyright
13: * notice, this list of conditions and the following disclaimer.
14: * 2. Redistributions in binary form must reproduce the above copyright
15: * notice, this list of conditions and the following disclaimer in the
16: * documentation and/or other materials provided with the distribution.
17: * 3. All advertising materials mentioning features or use of this software
18: * must display the following acknowledgement:
19: * This product includes software developed by Charles D. Cranor and
20: * Washington University.
21: * 4. The name of the author may not be used to endorse or promote products
22: * derived from this software without specific prior written permission.
23: *
24: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
25: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
26: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
27: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
28: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
29: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
30: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
31: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
32: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
33: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
34: */
35:
36: #ifndef _UVM_UVM_AMAP_H_
37: #define _UVM_UVM_AMAP_H_
38:
39: /*
40: * uvm_amap.h: general amap interface and amap implementation-specific info
41: */
42:
43: /*
44: * an amap structure contains pointers to a set of anons that are
45: * mapped together in virtual memory (an anon is a single page of
46: * anonymous virtual memory -- see uvm_anon.h). in uvm we hide the
47: * details of the implementation of amaps behind a general amap
48: * interface. this allows us to change the amap implementation
49: * without having to touch the rest of the code. this file is divided
50: * into two parts: the definition of the uvm amap interface and the
51: * amap implementation-specific definitions.
52: */
53:
54: #ifdef _KERNEL
55:
56: /*
57: * part 1: amap interface
58: */
59:
60: /*
61: * forward definition of vm_amap structure. only amap
62: * implementation-specific code should directly access the fields of
63: * this structure.
64: */
65:
66: struct vm_amap;
67:
68: /*
69: * handle inline options... we allow amap ops to be inline, but we also
70: * provide a hook to turn this off. macros can also be used.
71: */
72:
73: #ifdef UVM_AMAP_INLINE /* defined/undef'd in uvm_amap.c */
74: #define AMAP_INLINE static __inline /* inline enabled */
75: #else
76: #define AMAP_INLINE /* inline disabled */
77: #endif /* UVM_AMAP_INLINE */
78:
79:
80: /*
81: * prototypes for the amap interface
82: */
83:
84: AMAP_INLINE /* add an anon to an amap */
85: void amap_add(struct vm_aref *, vaddr_t, struct vm_anon *, boolean_t);
86: /* allocate a new amap */
87: struct vm_amap *amap_alloc(vaddr_t, vaddr_t, int);
88: /* clear amap needs-copy flag */
89: void amap_copy(vm_map_t, vm_map_entry_t, int, boolean_t, vaddr_t,
90: vaddr_t);
91: /* resolve all COW faults now */
92: void amap_cow_now(vm_map_t, vm_map_entry_t);
93: /* make amap larger */
94: int amap_extend(vm_map_entry_t, vsize_t);
95: /* get amap's flags */
96: int amap_flags(struct vm_amap *);
97: /* free amap */
98: void amap_free(struct vm_amap *);
99: /* init amap module (at boot time) */
100: void amap_init(void);
101: AMAP_INLINE /* lookup an anon @ offset in amap */
102: struct vm_anon *amap_lookup(struct vm_aref *, vaddr_t);
103: AMAP_INLINE /* lookup multiple anons */
104: void amap_lookups(struct vm_aref *, vaddr_t, struct vm_anon **, int);
105: AMAP_INLINE /* add a reference to an amap */
106: void amap_ref(struct vm_amap *, vaddr_t, vsize_t, int);
107: /* get number of references of amap */
108: int amap_refs(struct vm_amap *);
109: /* protect pages in a shared amap */
110: void amap_share_protect(vm_map_entry_t, vm_prot_t);
111: /* split reference to amap into two */
112: void amap_splitref(struct vm_aref *, struct vm_aref *, vaddr_t);
113: AMAP_INLINE /* remove an anon from an amap */
114: void amap_unadd(struct vm_aref *, vaddr_t);
115: AMAP_INLINE /* drop reference to an amap */
116: void amap_unref(struct vm_amap *, vaddr_t, vsize_t, int);
117: /* remove all anons from amap */
118: void amap_wipeout(struct vm_amap *);
119: boolean_t amap_swap_off(int, int);
120:
121: /*
122: * amap flag values
123: */
124:
125: #define AMAP_SHARED 0x1 /* amap is shared */
126: #define AMAP_REFALL 0x2 /* amap_ref: reference entire amap */
127: #define AMAP_SWAPOFF 0x4 /* amap_swap_off() is in progress */
128:
129: #endif /* _KERNEL */
130:
131: /**********************************************************************/
132:
133: /*
134: * part 2: amap implementation-specific info
135: */
136:
137: /*
138: * we currently provide an array-based amap implementation. in this
139: * implementation we provide the option of tracking split references
140: * so that we don't lose track of references during partial unmaps
141: * ... this is enabled with the "UVM_AMAP_PPREF" define.
142: */
143:
144: #define UVM_AMAP_PPREF /* track partial references */
145:
146: /*
147: * here is the definition of the vm_amap structure for this implementation.
148: */
149:
150: struct vm_amap {
151: int am_ref; /* reference count */
152: int am_flags; /* flags */
153: int am_maxslot; /* max # of slots allocated */
154: int am_nslot; /* # of slots currently in map ( <= maxslot) */
155: int am_nused; /* # of slots currently in use */
156: int *am_slots; /* contig array of active slots */
157: int *am_bckptr; /* back pointer array to am_slots */
158: struct vm_anon **am_anon; /* array of anonymous pages */
159: #ifdef UVM_AMAP_PPREF
160: int *am_ppref; /* per page reference count (if !NULL) */
161: #endif
162: LIST_ENTRY(vm_amap) am_list;
163: };
164:
165: /*
166: * note that am_slots, am_bckptr, and am_anon are arrays. this allows
167: * fast lookup of pages based on their virual address at the expense of
168: * some extra memory. in the future we should be smarter about memory
169: * usage and fall back to a non-array based implementation on systems
170: * that are short of memory (XXXCDC).
171: *
172: * the entries in the array are called slots... for example an amap that
173: * covers four pages of virtual memory is said to have four slots. here
174: * is an example of the array usage for a four slot amap. note that only
175: * slots one and three have anons assigned to them. "D/C" means that we
176: * "don't care" about the value.
177: *
178: * 0 1 2 3
179: * am_anon: NULL, anon0, NULL, anon1 (actual pointers to anons)
180: * am_bckptr: D/C, 1, D/C, 0 (points to am_slots entry)
181: *
182: * am_slots: 3, 1, D/C, D/C (says slots 3 and 1 are in use)
183: *
184: * note that am_bckptr is D/C if the slot in am_anon is set to NULL.
185: * to find the entry in am_slots for an anon, look at am_bckptr[slot],
186: * thus the entry for slot 3 in am_slots[] is at am_slots[am_bckptr[3]].
187: * in general, if am_anon[X] is non-NULL, then the following must be
188: * true: am_slots[am_bckptr[X]] == X
189: *
190: * note that am_slots is always contig-packed.
191: */
192:
193: /*
194: * defines for handling of large sparce amaps:
195: *
196: * one of the problems of array-based amaps is that if you allocate a
197: * large sparcely-used area of virtual memory you end up allocating
198: * large arrays that, for the most part, don't get used. this is a
199: * problem for BSD in that the kernel likes to make these types of
200: * allocations to "reserve" memory for possible future use.
201: *
202: * for example, the kernel allocates (reserves) a large chunk of user
203: * VM for possible stack growth. most of the time only a page or two
204: * of this VM is actually used. since the stack is anonymous memory
205: * it makes sense for it to live in an amap, but if we allocated an
206: * amap for the entire stack range we could end up wasting a large
207: * amount of malloc'd KVM.
208: *
209: * for example, on the i386 at boot time we allocate two amaps for the stack
210: * of /sbin/init:
211: * 1. a 7680 slot amap at protection 0 (reserve space for stack)
212: * 2. a 512 slot amap at protection 7 (top of stack)
213: *
214: * most of the array allocated for the amaps for this is never used.
215: * the amap interface provides a way for us to avoid this problem by
216: * allowing amap_copy() to break larger amaps up into smaller sized
217: * chunks (controlled by the "canchunk" option). we use this feature
218: * to reduce our memory usage with the BSD stack management. if we
219: * are asked to create an amap with more than UVM_AMAP_LARGE slots in it,
220: * we attempt to break it up into a UVM_AMAP_CHUNK sized amap if the
221: * "canchunk" flag is set.
222: *
223: * so, in the i386 example, the 7680 slot area is never referenced so
224: * nothing gets allocated (amap_copy is never called because the protection
225: * is zero). the 512 slot area for the top of the stack is referenced.
226: * the chunking code breaks it up into 16 slot chunks (hopefully a single
227: * 16 slot chunk is enough to handle the whole stack).
228: */
229:
230: #define UVM_AMAP_LARGE 256 /* # of slots in "large" amap */
231: #define UVM_AMAP_CHUNK 16 /* # of slots to chunk large amaps in */
232:
233: #ifdef _KERNEL
234:
235: /*
236: * macros
237: */
238:
239: /* AMAP_B2SLOT: convert byte offset to slot */
240: #define AMAP_B2SLOT(S,B) { \
241: KASSERT(((B) & (PAGE_SIZE - 1)) == 0); \
242: (S) = (B) >> PAGE_SHIFT; \
243: }
244:
245: /*
246: * lock/unlock/refs/flags macros
247: */
248:
249: #define amap_flags(AMAP) ((AMAP)->am_flags)
250: #define amap_refs(AMAP) ((AMAP)->am_ref)
251:
252: /*
253: * if we enable PPREF, then we have a couple of extra functions that
254: * we need to prototype here...
255: */
256:
257: #ifdef UVM_AMAP_PPREF
258:
259: #define PPREF_NONE ((int *) -1) /* not using ppref */
260:
261: /* adjust references */
262: void amap_pp_adjref(struct vm_amap *, int, vsize_t, int);
263: /* establish ppref */
264: void amap_pp_establish(struct vm_amap *);
265: /* wipe part of an amap */
266: void amap_wiperange(struct vm_amap *, int, int);
267: #endif /* UVM_AMAP_PPREF */
268:
269: #endif /* _KERNEL */
270:
271: #endif /* _UVM_UVM_AMAP_H_ */
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