280 lines
9.8 KiB
C
280 lines
9.8 KiB
C
/* $NetBSD: uvm_amap.h,v 1.37 2011/06/12 03:36:02 rmind Exp $ */
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/*
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* Copyright (c) 1997 Charles D. Cranor and Washington University.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef _UVM_UVM_AMAP_H_
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#define _UVM_UVM_AMAP_H_
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/*
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* uvm_amap.h: general amap interface and amap implementation-specific info
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*/
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/*
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* an amap structure contains pointers to a set of anons that are
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* mapped together in virtual memory (an anon is a single page of
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* anonymous virtual memory -- see uvm_anon.h). in uvm we hide the
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* details of the implementation of amaps behind a general amap
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* interface. this allows us to change the amap implementation
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* without having to touch the rest of the code. this file is divided
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* into two parts: the definition of the uvm amap interface and the
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* amap implementation-specific definitions.
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*/
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#ifdef _KERNEL
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/*
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* part 1: amap interface
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*/
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void uvm_amap_init(void);
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/*
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* forward definition of vm_amap structure. only amap
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* implementation-specific code should directly access the fields of
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* this structure.
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*/
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struct vm_amap;
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/*
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* prototypes for the amap interface
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*/
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void amap_add /* add an anon to an amap */
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(struct vm_aref *, vaddr_t,
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struct vm_anon *, bool);
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struct vm_amap *amap_alloc /* allocate a new amap */
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(vaddr_t, vaddr_t, int);
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void amap_copy /* clear amap needs-copy flag */
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(struct vm_map *, struct vm_map_entry *, int,
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vaddr_t, vaddr_t);
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void amap_cow_now /* resolve all COW faults now */
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(struct vm_map *, struct vm_map_entry *);
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int amap_extend /* make amap larger */
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(struct vm_map_entry *, vsize_t, int);
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int amap_flags /* get amap's flags */
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(struct vm_amap *);
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void amap_free /* free amap */
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(struct vm_amap *);
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void amap_lock /* lock amap */
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(struct vm_amap *);
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struct vm_anon *amap_lookup /* lookup an anon @ offset in amap */
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(struct vm_aref *, vaddr_t);
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void amap_lookups /* lookup multiple anons */
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(struct vm_aref *, vaddr_t,
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struct vm_anon **, int);
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void amap_ref /* add a reference to an amap */
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(struct vm_amap *, vaddr_t, vsize_t, int);
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int amap_refs /* get number of references of amap */
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(struct vm_amap *);
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void amap_share_protect /* protect pages in a shared amap */
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(struct vm_map_entry *, vm_prot_t);
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void amap_splitref /* split reference to amap into two */
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(struct vm_aref *, struct vm_aref *, vaddr_t);
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void amap_unadd /* remove an anon from an amap */
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(struct vm_aref *, vaddr_t);
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void amap_unlock /* unlock amap */
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(struct vm_amap *);
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void amap_unref /* drop reference to an amap */
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(struct vm_amap *, vaddr_t, vsize_t, bool);
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void amap_wipeout /* remove all anons from amap */
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(struct vm_amap *);
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bool amap_swap_off
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(int, int);
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/*
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* amap flag values
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*/
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#define AMAP_SHARED 0x1 /* amap is shared */
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#define AMAP_REFALL 0x2 /* amap_ref: reference entire amap */
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#define AMAP_SWAPOFF 0x4 /* amap_swap_off() is in progress */
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/*
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* amap_copy flags
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*/
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#define AMAP_COPY_NOWAIT 0x02 /* not allowed to sleep */
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#define AMAP_COPY_NOCHUNK 0x04 /* not allowed to chunk */
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#define AMAP_COPY_NOMERGE 0x08 /* not allowed to merge */
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/*
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* amap_extend flags
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*/
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#define AMAP_EXTEND_BACKWARDS 0x00 /* add "size" to start of map */
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#define AMAP_EXTEND_FORWARDS 0x01 /* add "size" to end of map */
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#define AMAP_EXTEND_NOWAIT 0x02 /* not allowed to sleep */
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#endif /* _KERNEL */
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/**********************************************************************/
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/*
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* part 2: amap implementation-specific info
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*/
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/*
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* we currently provide an array-based amap implementation. in this
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* implementation we provide the option of tracking split references
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* so that we don't lose track of references during partial unmaps
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* ... this is enabled with the "UVM_AMAP_PPREF" define.
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*/
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#define UVM_AMAP_PPREF /* track partial references */
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/*
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* here is the definition of the vm_amap structure for this implementation.
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*/
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struct vm_amap {
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kmutex_t *am_lock; /* lock [locks all vm_amap fields] */
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int am_ref; /* reference count */
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int am_flags; /* flags */
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int am_maxslot; /* max # of slots allocated */
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int am_nslot; /* # of slots currently in map ( <= maxslot) */
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int am_nused; /* # of slots currently in use */
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int *am_slots; /* contig array of active slots */
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int *am_bckptr; /* back pointer array to am_slots */
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struct vm_anon **am_anon; /* array of anonymous pages */
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#ifdef UVM_AMAP_PPREF
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int *am_ppref; /* per page reference count (if !NULL) */
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#endif
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LIST_ENTRY(vm_amap) am_list;
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};
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/*
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* note that am_slots, am_bckptr, and am_anon are arrays. this allows
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* fast lookup of pages based on their virual address at the expense of
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* some extra memory. in the future we should be smarter about memory
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* usage and fall back to a non-array based implementation on systems
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* that are short of memory (XXXCDC).
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*
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* the entries in the array are called slots... for example an amap that
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* covers four pages of virtual memory is said to have four slots. here
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* is an example of the array usage for a four slot amap. note that only
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* slots one and three have anons assigned to them. "D/C" means that we
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* "don't care" about the value.
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*
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* 0 1 2 3
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* am_anon: NULL, anon0, NULL, anon1 (actual pointers to anons)
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* am_bckptr: D/C, 1, D/C, 0 (points to am_slots entry)
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*
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* am_slots: 3, 1, D/C, D/C (says slots 3 and 1 are in use)
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*
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* note that am_bckptr is D/C if the slot in am_anon is set to NULL.
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* to find the entry in am_slots for an anon, look at am_bckptr[slot],
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* thus the entry for slot 3 in am_slots[] is at am_slots[am_bckptr[3]].
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* in general, if am_anon[X] is non-NULL, then the following must be
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* true: am_slots[am_bckptr[X]] == X
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*
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* note that am_slots is always contig-packed.
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*/
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/*
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* defines for handling of large, sparse amaps:
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*
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* one of the problems of array-based amaps is that if you allocate a
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* large, sparsely-used area of virtual memory you end up allocating
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* large arrays that, for the most part, don't get used. this is a
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* problem for BSD in that the kernel likes to make these types of
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* allocations to "reserve" memory for possible future use.
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*
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* for example, the kernel allocates (reserves) a large chunk of user
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* VM for possible stack growth. most of the time only a page or two
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* of this VM is actually used. since the stack is anonymous memory
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* it makes sense for it to live in an amap, but if we allocated an
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* amap for the entire stack range we could end up wasting a large
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* amount of allocated KVM.
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*
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* for example, on the i386 at boot time we allocate two amaps for the stack
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* of /sbin/init:
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* 1. a 7680 slot amap at protection 0 (reserve space for stack)
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* 2. a 512 slot amap at protection 7 (top of stack)
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*
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* most of the array allocated for the amaps for this is never used.
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* the amap interface provides a way for us to avoid this problem by
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* allowing amap_copy() to break larger amaps up into smaller sized
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* chunks (controlled by the "canchunk" option). we use this feature
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* to reduce our memory usage with the BSD stack management. if we
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* are asked to create an amap with more than UVM_AMAP_LARGE slots in it,
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* we attempt to break it up into a UVM_AMAP_CHUNK sized amap if the
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* "canchunk" flag is set.
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*
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* so, in the i386 example, the 7680 slot area is never referenced so
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* nothing gets allocated (amap_copy is never called because the protection
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* is zero). the 512 slot area for the top of the stack is referenced.
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* the chunking code breaks it up into 16 slot chunks (hopefully a single
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* 16 slot chunk is enough to handle the whole stack).
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*/
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#define UVM_AMAP_LARGE 256 /* # of slots in "large" amap */
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#define UVM_AMAP_CHUNK 16 /* # of slots to chunk large amaps in */
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#ifdef _KERNEL
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/*
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* macros
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*/
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/* AMAP_B2SLOT: convert byte offset to slot */
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#define AMAP_B2SLOT(S,B) { \
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KASSERT(((B) & (PAGE_SIZE - 1)) == 0); \
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(S) = (B) >> PAGE_SHIFT; \
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}
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/*
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* lock/unlock/refs/flags macros
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*/
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#define amap_flags(AMAP) ((AMAP)->am_flags)
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#define amap_lock(AMAP) mutex_enter((AMAP)->am_lock)
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#define amap_lock_try(AMAP) mutex_tryenter((AMAP)->am_lock)
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#define amap_refs(AMAP) ((AMAP)->am_ref)
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#define amap_unlock(AMAP) mutex_exit((AMAP)->am_lock)
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/*
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* if we enable PPREF, then we have a couple of extra functions that
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* we need to prototype here...
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*/
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#ifdef UVM_AMAP_PPREF
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#define PPREF_NONE ((int *) -1) /* not using ppref */
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void amap_pp_adjref /* adjust references */
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(struct vm_amap *, int, vsize_t, int,
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struct vm_anon **);
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void amap_pp_establish /* establish ppref */
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(struct vm_amap *, vaddr_t);
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void amap_wiperange /* wipe part of an amap */
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(struct vm_amap *, int, int, struct vm_anon **);
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#endif /* UVM_AMAP_PPREF */
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#endif /* _KERNEL */
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#endif /* _UVM_UVM_AMAP_H_ */
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