/* $NetBSD: uvm_amap.h,v 1.29 2006/02/15 14:06:45 yamt 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 */ /* * 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 *, boolean_t); 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, int); void amap_wipeout /* remove all anons from amap */ (struct vm_amap *); boolean_t 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 { struct simplelock am_l; /* simple 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 sparce amaps: * * one of the problems of array-based amaps is that if you allocate a * large sparcely-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 #include MALLOC_DECLARE(M_UVMAMAP); /* * 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) simple_lock(&(AMAP)->am_l) #define amap_lock_try(AMAP) simple_lock_try(&(AMAP)->am_l) #define amap_refs(AMAP) ((AMAP)->am_ref) #define amap_unlock(AMAP) simple_unlock(&(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_ */