kernel/mem/pagealloc.cc

   1 // mem/pagealloc.cc -- low-level page allocator
   2 //
   3 // This software is copyright (c) 2006 Scott Wood <scott@buserror.net>.
   4 //
   5 // Permission is hereby granted, free of charge, to any person obtaining a copy of
   6 // this software and associated documentation files (the "Software"), to deal with
   7 // the Software without restriction, including without limitation the rights to
   8 // use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
   9 // of the Software, and to permit persons to whom the Software is furnished to do
  10 // so, subject to the following condition:
  11 //
  12 // The above copyright notice and this permission notice shall be
  13 // included in all copies or substantial portions of the Software.
  14 //
  15 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
  17 // FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
  18 // CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  20 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS WITH THE
  21 // SOFTWARE.
  22
  23 #include <kern/kernel.h>
  24 #include <kern/pagealloc.h>
  25 #include <kern/paging.h>
  26 #include <kern/bitops.h>
  27 #include <kern/list.h>
  28 #include <kern/mem.h>
  29 #include <limits.h>
  30
  31 namespace Mem {
  32         Page *pages, *last_page;
  33         inline size_t PageAllocZone::chunk_size(Page *start)
  34         {
  35                 ptrdiff_t ret = start->free.otherside - start + 1;
  36                 assert(ret >= 1);
  37                 assert(static_cast<size_t>(ret) <= zonesize);
  38                 return static_cast<size_t>(ret);
  39         }
  40
  41         inline Page *PageAllocZone::bin_to_head(int bin)
  42         {
  43                 return &bins[bin];
  44         }
  45
  46         inline uint PageAllocZone::bin_to_size(int bin)
  47         {
  48                 return 1 << bin;
  49         }
  50
  51         inline int PageAllocZone::size_to_bin_alloc(size_t size)
  52         {
  53                 int bin = ll_get_order_round_up(size);
  54
  55                 if (bin >= num_bins)
  56                         bin = num_bins - 1;
  57
  58                 return bin;
  59         }
  60
  61         inline int PageAllocZone::size_to_bin_free(size_t size)
  62         {
  63                 int bin = ll_get_order_round_down(size);
  64
  65                 if (bin >= num_bins)
  66                         bin = num_bins - 1;
  67
  68                 return bin;
  69         }
  70
  71         inline void PageAllocZone::remove_chunk(Page *chunk, int bin)
  72         {
  73                 chunk->chunk_rmap_list.del();
  74
  75                 // If bin's list is empty, forward it to the next non-empty bin.
  76
  77                 Page *head = bin_to_head(bin);
  78                 if (head->chunk_rmap_list.empty()) {
  79                         Page *newforward = bin_to_head(bin + 1)->free.otherside;
  80                         assert(head->free.otherside == head);
  81
  82                         for (Page *p = head;
  83                              p - bins >= 0 && p->free.otherside == head; p--)
  84                                 p->free.otherside = newforward;
  85                 }
  86         }
  87
  88         inline void PageAllocZone::add_to_bin(Page *chunk, int bin)
  89         {
  90                 Page *head = bin_to_head(bin);
  91                 Page *oldforward = head->free.otherside;
  92
  93                 head->chunk_rmap_list.add_front(&chunk->chunk_rmap_list);
  94
  95                 // Remove bin's forwarding if it was empty, along with smaller
  96                 // bins pointing past this bin.
  97
  98                 if (oldforward != head) {
  99                         Page *p = head;
 100                         do {
 101                                 p->free.otherside = head;
 102                                 p--;
 103                         } while (p - bins >= 0 && p->free.otherside == oldforward);
 104                 }
 105         }
 106
 107         // Break off a piece from the end of the chunk, rather than the start.
 108         // This way, only the size of the remaining chunk needs to be adjusted
 109         // as long as it still fits in the same bin.
 110
 111         Page *PageAllocZone::shrink_chunk(Page *start, int num_pages,
 112                                           size_t chunk_size, int bin)
 113         {
 114                 size_t size_left = chunk_size - num_pages;
 115                 Page *newend = start + size_left - 1;
 116
 117                 start->free.otherside = newend;
 118                 newend->free.otherside = start;
 119
 120                 if (size_left < bin_to_size(bin)) {
 121                         remove_chunk(start, bin);
 122                         add_to_bin(start, size_to_bin_alloc(size_left));
 123                 }
 124
 125                 return newend + 1;
 126         }
 127
 128         struct Page *PageAllocZone::alloc(uint num_pages)
 129         {
 130                 Lock::AutoSpinLockRecIRQ autolock(lock);
 131
 132                 assert(num_pages > 0);
 133                 assert(num_pages <= bin_to_size(num_bins - 1));
 134
 135                 int bin = size_to_bin_alloc(num_pages);
 136                 Page *head = bin_to_head(bin)->free.otherside;
 137                 int realbin = head - bins;
 138                 Util::List *list = &head->chunk_rmap_list;
 139
 140                 if (list->empty()) {
 141                         assert(realbin == num_bins - 1);
 142                         return NULL;
 143                 }
 144
 145                 head = list->next->listentry(Page, chunk_rmap_list);
 146
 147                 assert(head->flags & Page::Free);
 148
 149                 size_t size = chunk_size(head);
 150                 assert(size >= bin_to_size(bin));
 151                 assert(size >= (uint)num_pages);
 152
 153                 if (size != num_pages)
 154                         head = shrink_chunk(head, num_pages, size, realbin);
 155                 else
 156                         remove_chunk(head, realbin);
 157
 158                 for (Page *p = head; p != head + num_pages; p++) {
 159                         assert(p->flags & Page::Free);
 160                         assert(!(p->flags & Page::InUse));
 161                         assert(p->chunk_rmap_list.empty());
 162                         p->flags = (p->flags & ~Page::Free) | Page::InUse;
 163                         p->inuse.refcount = 1;
 164                 }
 165
 166                 return head;
 167         }
 168
 169         void PageAllocZone::free(struct Page *head, size_t num_pages)
 170         {
 171                 Lock::AutoSpinLockRecIRQ autolock(lock);
 172
 173                 assert(num_pages > 0);
 174
 175                 for (Page *p = head; p != head + num_pages; p++) {
 176                         assert(!(p->flags & Page::Free));
 177                         assert(p->chunk_rmap_list.empty());
 178                         p->flags = (p->flags & ~Page::InUse) | Page::Free;
 179                 }
 180
 181                 // Combine the newly free chunk with any adjacent free chunks,
 182                 // regardless of what bin they are in.
 183
 184                 Page *prevpage = head - 1;
 185                 Page *nextpage = head + num_pages;
 186
 187                 int bin = -1;
 188
 189                 if (prevpage - pages >= start && (prevpage->flags & Page::Free)) {
 190                         Page *prevchunk = prevpage->free.otherside;
 191                         assert(prevchunk->flags & Page::Free);
 192
 193                         Page *end = head + num_pages - 1;
 194                         prevchunk->free.otherside = end;
 195                         end->free.otherside = prevchunk;
 196
 197                         size_t prevsize = head - prevchunk;
 198                         assert(prevsize > 0);
 199                         assert(prevsize < zonesize);
 200
 201                         head = prevchunk;
 202                         num_pages += prevsize;
 203                         bin = size_to_bin_free(prevsize);
 204                 }
 205
 206                 if (nextpage - pages <= end && nextpage->flags & Page::Free) {
 207                         size_t prevsize = chunk_size(nextpage);
 208                         num_pages += prevsize;
 209                         Page *end = nextpage->free.otherside;
 210
 211                         remove_chunk(nextpage, size_to_bin_free(prevsize));
 212
 213                         end->free.otherside = head;
 214                         head->free.otherside = end;
 215                 }
 216
 217                 int newbin = size_to_bin_free(num_pages);
 218
 219                 if (bin != newbin) {
 220                         if (bin != -1) {
 221                                 remove_chunk(head, bin);
 222                                 assert(head->free.otherside == head + num_pages - 1);
 223                         }
 224
 225                         head->free.otherside = head + num_pages - 1;
 226                         add_to_bin(head, newbin);
 227                 }
 228         }
 229
 230         void PageAllocZone::init(uintptr_t base, size_t size)
 231         {
 232                 assert(size > 0);
 233                 assert(base + size <= Arch::mem_end / Arch::page_size);
 234
 235                 zonesize = size;
 236                 start = base;
 237                 end = base + size - 1;
 238
 239                 for (Page *p = &pages[start]; p <= &pages[end]; p++) {
 240                         assert(p->flags == 0);
 241                         new(p) Page;
 242                         p->zone = this;
 243                 }
 244
 245                 for (int i = 0; i < num_bins; i++) {
 246                         Page *bin = bin_to_head(i);
 247
 248                         bin->free.otherside = bin_to_head(num_bins - 1);
 249                         bin->chunk_rmap_list.init();
 250                 }
 251         }
 252
 253         Page *PageAlloc::alloc(uint num_pages, PageAllocZone *const *zonelist)
 254         {
 255                 while (*zonelist) {
 256                         Page *ret = (*zonelist)->alloc(num_pages);
 257                         if (ret)
 258                                 return ret;
 259
 260                         zonelist++;
 261                 }
 262
 263                 // FIXME: Deliver System.Traps.ReduceMemoryUsage first
 264                 throw_idl(OutOfMemory);
 265         }
 266
 267         void Page::free_page()
 268         {
 269                 PageAlloc::free(this, 1);
 270         }
 271
 272         PageAlloc page_alloc;
 273 }