gdb/dcache.c

   1 /* Caching code for GDB, the GNU debugger.
   2
   3    Copyright (C) 1992-2019 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "defs.h"
  21 #include "dcache.h"
  22 #include "gdbcmd.h"
  23 #include "gdbcore.h"
  24 #include "target-dcache.h"
  25 #include "inferior.h"
  26 #include "splay-tree.h"
  27
  28 /* Commands with a prefix of `{set,show} dcache'.  */
  29 static struct cmd_list_element *dcache_set_list = NULL;
  30 static struct cmd_list_element *dcache_show_list = NULL;
  31
  32 /* The data cache could lead to incorrect results because it doesn't
  33    know about volatile variables, thus making it impossible to debug
  34    functions which use memory mapped I/O devices.  Set the nocache
  35    memory region attribute in those cases.
  36
  37    In general the dcache speeds up performance.  Some speed improvement
  38    comes from the actual caching mechanism, but the major gain is in
  39    the reduction of the remote protocol overhead; instead of reading
  40    or writing a large area of memory in 4 byte requests, the cache
  41    bundles up the requests into LINE_SIZE chunks, reducing overhead
  42    significantly.  This is most useful when accessing a large amount
  43    of data, such as when performing a backtrace.
  44
  45    The cache is a splay tree along with a linked list for replacement.
  46    Each block caches a LINE_SIZE area of memory.  Within each line we
  47    remember the address of the line (which must be a multiple of
  48    LINE_SIZE) and the actual data block.
  49
  50    Lines are only allocated as needed, so DCACHE_SIZE really specifies the
  51    *maximum* number of lines in the cache.
  52
  53    At present, the cache is write-through rather than writeback: as soon
  54    as data is written to the cache, it is also immediately written to
  55    the target.  Therefore, cache lines are never "dirty".  Whether a given
  56    line is valid or not depends on where it is stored in the dcache_struct;
  57    there is no per-block valid flag.  */
  58
  59 /* NOTE: Interaction of dcache and memory region attributes
  60
  61    As there is no requirement that memory region attributes be aligned
  62    to or be a multiple of the dcache page size, dcache_read_line() and
  63    dcache_write_line() must break up the page by memory region.  If a
  64    chunk does not have the cache attribute set, an invalid memory type
  65    is set, etc., then the chunk is skipped.  Those chunks are handled
  66    in target_xfer_memory() (or target_xfer_memory_partial()).
  67
  68    This doesn't occur very often.  The most common occurance is when
  69    the last bit of the .text segment and the first bit of the .data
  70    segment fall within the same dcache page with a ro/cacheable memory
  71    region defined for the .text segment and a rw/non-cacheable memory
  72    region defined for the .data segment.  */
  73
  74 /* The maximum number of lines stored.  The total size of the cache is
  75    equal to DCACHE_SIZE times LINE_SIZE.  */
  76 #define DCACHE_DEFAULT_SIZE 4096
  77 static unsigned dcache_size = DCACHE_DEFAULT_SIZE;
  78
  79 /* The default size of a cache line.  Smaller values reduce the time taken to
  80    read a single byte and make the cache more granular, but increase
  81    overhead and reduce the effectiveness of the cache as a prefetcher.  */
  82 #define DCACHE_DEFAULT_LINE_SIZE 64
  83 static unsigned dcache_line_size = DCACHE_DEFAULT_LINE_SIZE;
  84
  85 /* Each cache block holds LINE_SIZE bytes of data
  86    starting at a multiple-of-LINE_SIZE address.  */
  87
  88 #define LINE_SIZE_MASK(dcache)  ((dcache->line_size - 1))
  89 #define XFORM(dcache, x)        ((x) & LINE_SIZE_MASK (dcache))
  90 #define MASK(dcache, x)         ((x) & ~LINE_SIZE_MASK (dcache))
  91
  92 struct dcache_block
  93 {
  94   /* For least-recently-allocated and free lists.  */
  95   struct dcache_block *prev;
  96   struct dcache_block *next;
  97
  98   CORE_ADDR addr;               /* address of data */
  99   int refs;                     /* # hits */
 100   gdb_byte data[1];             /* line_size bytes at given address */
 101 };
 102
 103 struct dcache_struct
 104 {
 105   splay_tree tree;
 106   struct dcache_block *oldest; /* least-recently-allocated list.  */
 107
 108   /* The free list is maintained identically to OLDEST to simplify
 109      the code: we only need one set of accessors.  */
 110   struct dcache_block *freelist;
 111
 112   /* The number of in-use lines in the cache.  */
 113   int size;
 114   CORE_ADDR line_size;  /* current line_size.  */
 115
 116   /* The ptid of last inferior to use cache or null_ptid.  */
 117   ptid_t ptid;
 118 };
 119
 120 typedef void (block_func) (struct dcache_block *block, void *param);
 121
 122 static struct dcache_block *dcache_hit (DCACHE *dcache, CORE_ADDR addr);
 123
 124 static int dcache_read_line (DCACHE *dcache, struct dcache_block *db);
 125
 126 static struct dcache_block *dcache_alloc (DCACHE *dcache, CORE_ADDR addr);
 127
 128 static int dcache_enabled_p = 0; /* OBSOLETE */
 129
 130 static void
 131 show_dcache_enabled_p (struct ui_file *file, int from_tty,
 132                        struct cmd_list_element *c, const char *value)
 133 {
 134   fprintf_filtered (file, _("Deprecated remotecache flag is %s.\n"), value);
 135 }
 136
 137 /* Add BLOCK to circular block list BLIST, behind the block at *BLIST.
 138    *BLIST is not updated (unless it was previously NULL of course).
 139    This is for the least-recently-allocated list's sake:
 140    BLIST points to the oldest block.
 141    ??? This makes for poor cache usage of the free list,
 142    but is it measurable?  */
 143
 144 static void
 145 append_block (struct dcache_block **blist, struct dcache_block *block)
 146 {
 147   if (*blist)
 148     {
 149       block->next = *blist;
 150       block->prev = (*blist)->prev;
 151       block->prev->next = block;
 152       (*blist)->prev = block;
 153       /* We don't update *BLIST here to maintain the invariant that for the
 154          least-recently-allocated list *BLIST points to the oldest block.  */
 155     }
 156   else
 157     {
 158       block->next = block;
 159       block->prev = block;
 160       *blist = block;
 161     }
 162 }
 163
 164 /* Remove BLOCK from circular block list BLIST.  */
 165
 166 static void
 167 remove_block (struct dcache_block **blist, struct dcache_block *block)
 168 {
 169   if (block->next == block)
 170     {
 171       *blist = NULL;
 172     }
 173   else
 174     {
 175       block->next->prev = block->prev;
 176       block->prev->next = block->next;
 177       /* If we removed the block *BLIST points to, shift it to the next block
 178          to maintain the invariant that for the least-recently-allocated list
 179          *BLIST points to the oldest block.  */
 180       if (*blist == block)
 181         *blist = block->next;
 182     }
 183 }
 184
 185 /* Iterate over all elements in BLIST, calling FUNC.
 186    PARAM is passed to FUNC.
 187    FUNC may remove the block it's passed, but only that block.  */
 188
 189 static void
 190 for_each_block (struct dcache_block **blist, block_func *func, void *param)
 191 {
 192   struct dcache_block *db;
 193
 194   if (*blist == NULL)
 195     return;
 196
 197   db = *blist;
 198   do
 199     {
 200       struct dcache_block *next = db->next;
 201
 202       func (db, param);
 203       db = next;
 204     }
 205   while (*blist && db != *blist);
 206 }
 207
 208 /* BLOCK_FUNC routine for dcache_free.  */
 209
 210 static void
 211 free_block (struct dcache_block *block, void *param)
 212 {
 213   xfree (block);
 214 }
 215
 216 /* Free a data cache.  */
 217
 218 void
 219 dcache_free (DCACHE *dcache)
 220 {
 221   splay_tree_delete (dcache->tree);
 222   for_each_block (&dcache->oldest, free_block, NULL);
 223   for_each_block (&dcache->freelist, free_block, NULL);
 224   xfree (dcache);
 225 }
 226
 227
 228 /* BLOCK_FUNC function for dcache_invalidate.
 229    This doesn't remove the block from the oldest list on purpose.
 230    dcache_invalidate will do it later.  */
 231
 232 static void
 233 invalidate_block (struct dcache_block *block, void *param)
 234 {
 235   DCACHE *dcache = (DCACHE *) param;
 236
 237   splay_tree_remove (dcache->tree, (splay_tree_key) block->addr);
 238   append_block (&dcache->freelist, block);
 239 }
 240
 241 /* Free all the data cache blocks, thus discarding all cached data.  */
 242
 243 void
 244 dcache_invalidate (DCACHE *dcache)
 245 {
 246   for_each_block (&dcache->oldest, invalidate_block, dcache);
 247
 248   dcache->oldest = NULL;
 249   dcache->size = 0;
 250   dcache->ptid = null_ptid;
 251
 252   if (dcache->line_size != dcache_line_size)
 253     {
 254       /* We've been asked to use a different line size.
 255          All of our freelist blocks are now the wrong size, so free them.  */
 256
 257       for_each_block (&dcache->freelist, free_block, dcache);
 258       dcache->freelist = NULL;
 259       dcache->line_size = dcache_line_size;
 260     }
 261 }
 262
 263 /* Invalidate the line associated with ADDR.  */
 264
 265 static void
 266 dcache_invalidate_line (DCACHE *dcache, CORE_ADDR addr)
 267 {
 268   struct dcache_block *db = dcache_hit (dcache, addr);
 269
 270   if (db)
 271     {
 272       splay_tree_remove (dcache->tree, (splay_tree_key) db->addr);
 273       remove_block (&dcache->oldest, db);
 274       append_block (&dcache->freelist, db);
 275       --dcache->size;
 276     }
 277 }
 278
 279 /* If addr is present in the dcache, return the address of the block
 280    containing it.  Otherwise return NULL.  */
 281
 282 static struct dcache_block *
 283 dcache_hit (DCACHE *dcache, CORE_ADDR addr)
 284 {
 285   struct dcache_block *db;
 286
 287   splay_tree_node node = splay_tree_lookup (dcache->tree,
 288                                             (splay_tree_key) MASK (dcache, addr));
 289
 290   if (!node)
 291     return NULL;
 292
 293   db = (struct dcache_block *) node->value;
 294   db->refs++;
 295   return db;
 296 }
 297
 298 /* Fill a cache line from target memory.
 299    The result is 1 for success, 0 if the (entire) cache line
 300    wasn't readable.  */
 301
 302 static int
 303 dcache_read_line (DCACHE *dcache, struct dcache_block *db)
 304 {
 305   CORE_ADDR memaddr;
 306   gdb_byte *myaddr;
 307   int len;
 308   int res;
 309   int reg_len;
 310   struct mem_region *region;
 311
 312   len = dcache->line_size;
 313   memaddr = db->addr;
 314   myaddr  = db->data;
 315
 316   while (len > 0)
 317     {
 318       /* Don't overrun if this block is right at the end of the region.  */
 319       region = lookup_mem_region (memaddr);
 320       if (region->hi == 0 || memaddr + len < region->hi)
 321         reg_len = len;
 322       else
 323         reg_len = region->hi - memaddr;
 324
 325       /* Skip non-readable regions.  The cache attribute can be ignored,
 326          since we may be loading this for a stack access.  */
 327       if (region->attrib.mode == MEM_WO)
 328         {
 329           memaddr += reg_len;
 330           myaddr  += reg_len;
 331           len     -= reg_len;
 332           continue;
 333         }
 334
 335       res = target_read_raw_memory (memaddr, myaddr, reg_len);
 336       if (res != 0)
 337         return 0;
 338
 339       memaddr += reg_len;
 340       myaddr += reg_len;
 341       len -= reg_len;
 342     }
 343
 344   return 1;
 345 }
 346
 347 /* Get a free cache block, put or keep it on the valid list,
 348    and return its address.  */
 349
 350 static struct dcache_block *
 351 dcache_alloc (DCACHE *dcache, CORE_ADDR addr)
 352 {
 353   struct dcache_block *db;
 354
 355   if (dcache->size >= dcache_size)
 356     {
 357       /* Evict the least recently allocated line.  */
 358       db = dcache->oldest;
 359       remove_block (&dcache->oldest, db);
 360
 361       splay_tree_remove (dcache->tree, (splay_tree_key) db->addr);
 362     }
 363   else
 364     {
 365       db = dcache->freelist;
 366       if (db)
 367         remove_block (&dcache->freelist, db);
 368       else
 369         db = ((struct dcache_block *)
 370               xmalloc (offsetof (struct dcache_block, data)
 371                        + dcache->line_size));
 372
 373       dcache->size++;
 374     }
 375
 376   db->addr = MASK (dcache, addr);
 377   db->refs = 0;
 378
 379   /* Put DB at the end of the list, it's the newest.  */
 380   append_block (&dcache->oldest, db);
 381
 382   splay_tree_insert (dcache->tree, (splay_tree_key) db->addr,
 383                      (splay_tree_value) db);
 384
 385   return db;
 386 }
 387
 388 /* Using the data cache DCACHE, store in *PTR the contents of the byte at
 389    address ADDR in the remote machine.
 390
 391    Returns 1 for success, 0 for error.  */
 392
 393 static int
 394 dcache_peek_byte (DCACHE *dcache, CORE_ADDR addr, gdb_byte *ptr)
 395 {
 396   struct dcache_block *db = dcache_hit (dcache, addr);
 397
 398   if (!db)
 399     {
 400       db = dcache_alloc (dcache, addr);
 401
 402       if (!dcache_read_line (dcache, db))
 403          return 0;
 404     }
 405
 406   *ptr = db->data[XFORM (dcache, addr)];
 407   return 1;
 408 }
 409
 410 /* Write the byte at PTR into ADDR in the data cache.
 411
 412    The caller should have written the data through to target memory
 413    already.
 414
 415    If ADDR is not in cache, this function does nothing; writing to an
 416    area of memory which wasn't present in the cache doesn't cause it
 417    to be loaded in.  */
 418
 419 static void
 420 dcache_poke_byte (DCACHE *dcache, CORE_ADDR addr, const gdb_byte *ptr)
 421 {
 422   struct dcache_block *db = dcache_hit (dcache, addr);
 423
 424   if (db)
 425     db->data[XFORM (dcache, addr)] = *ptr;
 426 }
 427
 428 static int
 429 dcache_splay_tree_compare (splay_tree_key a, splay_tree_key b)
 430 {
 431   if (a > b)
 432     return 1;
 433   else if (a == b)
 434     return 0;
 435   else
 436     return -1;
 437 }
 438
 439 /* Allocate and initialize a data cache.  */
 440
 441 DCACHE *
 442 dcache_init (void)
 443 {
 444   DCACHE *dcache = XNEW (DCACHE);
 445
 446   dcache->tree = splay_tree_new (dcache_splay_tree_compare,
 447                                  NULL,
 448                                  NULL);
 449
 450   dcache->oldest = NULL;
 451   dcache->freelist = NULL;
 452   dcache->size = 0;
 453   dcache->line_size = dcache_line_size;
 454   dcache->ptid = null_ptid;
 455
 456   return dcache;
 457 }
 458
 459
 460 /* Read LEN bytes from dcache memory at MEMADDR, transferring to
 461    debugger address MYADDR.  If the data is presently cached, this
 462    fills the cache.  Arguments/return are like the target_xfer_partial
 463    interface.  */
 464
 465 enum target_xfer_status
 466 dcache_read_memory_partial (struct target_ops *ops, DCACHE *dcache,
 467                             CORE_ADDR memaddr, gdb_byte *myaddr,
 468                             ULONGEST len, ULONGEST *xfered_len)
 469 {
 470   ULONGEST i;
 471
 472   /* If this is a different inferior from what we've recorded,
 473      flush the cache.  */
 474
 475   if (inferior_ptid != dcache->ptid)
 476     {
 477       dcache_invalidate (dcache);
 478       dcache->ptid = inferior_ptid;
 479     }
 480
 481   for (i = 0; i < len; i++)
 482     {
 483       if (!dcache_peek_byte (dcache, memaddr + i, myaddr + i))
 484         {
 485           /* That failed.  Discard its cache line so we don't have a
 486              partially read line.  */
 487           dcache_invalidate_line (dcache, memaddr + i);
 488           break;
 489         }
 490     }
 491
 492   if (i == 0)
 493     {
 494       /* Even though reading the whole line failed, we may be able to
 495          read a piece starting where the caller wanted.  */
 496       return raw_memory_xfer_partial (ops, myaddr, NULL, memaddr, len,
 497                                       xfered_len);
 498     }
 499   else
 500     {
 501       *xfered_len = i;
 502       return TARGET_XFER_OK;
 503     }
 504 }
 505
 506 /* FIXME: There would be some benefit to making the cache write-back and
 507    moving the writeback operation to a higher layer, as it could occur
 508    after a sequence of smaller writes have been completed (as when a stack
 509    frame is constructed for an inferior function call).  Note that only
 510    moving it up one level to target_xfer_memory[_partial]() is not
 511    sufficient since we want to coalesce memory transfers that are
 512    "logically" connected but not actually a single call to one of the
 513    memory transfer functions.  */
 514
 515 /* Just update any cache lines which are already present.  This is
 516    called by the target_xfer_partial machinery when writing raw
 517    memory.  */
 518
 519 void
 520 dcache_update (DCACHE *dcache, enum target_xfer_status status,
 521                CORE_ADDR memaddr, const gdb_byte *myaddr,
 522                ULONGEST len)
 523 {
 524   ULONGEST i;
 525
 526   for (i = 0; i < len; i++)
 527     if (status == TARGET_XFER_OK)
 528       dcache_poke_byte (dcache, memaddr + i, myaddr + i);
 529     else
 530       {
 531         /* Discard the whole cache line so we don't have a partially
 532            valid line.  */
 533         dcache_invalidate_line (dcache, memaddr + i);
 534       }
 535 }
 536
 537 /* Print DCACHE line INDEX.  */
 538
 539 static void
 540 dcache_print_line (DCACHE *dcache, int index)
 541 {
 542   splay_tree_node n;
 543   struct dcache_block *db;
 544   int i, j;
 545
 546   if (dcache == NULL)
 547     {
 548       printf_filtered (_("No data cache available.\n"));
 549       return;
 550     }
 551
 552   n = splay_tree_min (dcache->tree);
 553
 554   for (i = index; i > 0; --i)
 555     {
 556       if (!n)
 557         break;
 558       n = splay_tree_successor (dcache->tree, n->key);
 559     }
 560
 561   if (!n)
 562     {
 563       printf_filtered (_("No such cache line exists.\n"));
 564       return;
 565     }
 566
 567   db = (struct dcache_block *) n->value;
 568
 569   printf_filtered (_("Line %d: address %s [%d hits]\n"),
 570                    index, paddress (target_gdbarch (), db->addr), db->refs);
 571
 572   for (j = 0; j < dcache->line_size; j++)
 573     {
 574       printf_filtered ("%02x ", db->data[j]);
 575
 576       /* Print a newline every 16 bytes (48 characters).  */
 577       if ((j % 16 == 15) && (j != dcache->line_size - 1))
 578         printf_filtered ("\n");
 579     }
 580   printf_filtered ("\n");
 581 }
 582
 583 /* Parse EXP and show the info about DCACHE.  */
 584
 585 static void
 586 dcache_info_1 (DCACHE *dcache, const char *exp)
 587 {
 588   splay_tree_node n;
 589   int i, refcount;
 590
 591   if (exp)
 592     {
 593       char *linestart;
 594
 595       i = strtol (exp, &linestart, 10);
 596       if (linestart == exp || i < 0)
 597         {
 598           printf_filtered (_("Usage: info dcache [LINENUMBER]\n"));
 599           return;
 600         }
 601
 602       dcache_print_line (dcache, i);
 603       return;
 604     }
 605
 606   printf_filtered (_("Dcache %u lines of %u bytes each.\n"),
 607                    dcache_size,
 608                    dcache ? (unsigned) dcache->line_size
 609                    : dcache_line_size);
 610
 611   if (dcache == NULL || dcache->ptid == null_ptid)
 612     {
 613       printf_filtered (_("No data cache available.\n"));
 614       return;
 615     }
 616
 617   printf_filtered (_("Contains data for %s\n"),
 618                    target_pid_to_str (dcache->ptid).c_str ());
 619
 620   refcount = 0;
 621
 622   n = splay_tree_min (dcache->tree);
 623   i = 0;
 624
 625   while (n)
 626     {
 627       struct dcache_block *db = (struct dcache_block *) n->value;
 628
 629       printf_filtered (_("Line %d: address %s [%d hits]\n"),
 630                        i, paddress (target_gdbarch (), db->addr), db->refs);
 631       i++;
 632       refcount += db->refs;
 633
 634       n = splay_tree_successor (dcache->tree, n->key);
 635     }
 636
 637   printf_filtered (_("Cache state: %d active lines, %d hits\n"), i, refcount);
 638 }
 639
 640 static void
 641 info_dcache_command (const char *exp, int tty)
 642 {
 643   dcache_info_1 (target_dcache_get (), exp);
 644 }
 645
 646 static void
 647 set_dcache_size (const char *args, int from_tty,
 648                  struct cmd_list_element *c)
 649 {
 650   if (dcache_size == 0)
 651     {
 652       dcache_size = DCACHE_DEFAULT_SIZE;
 653       error (_("Dcache size must be greater than 0."));
 654     }
 655   target_dcache_invalidate ();
 656 }
 657
 658 static void
 659 set_dcache_line_size (const char *args, int from_tty,
 660                       struct cmd_list_element *c)
 661 {
 662   if (dcache_line_size < 2
 663       || (dcache_line_size & (dcache_line_size - 1)) != 0)
 664     {
 665       unsigned d = dcache_line_size;
 666       dcache_line_size = DCACHE_DEFAULT_LINE_SIZE;
 667       error (_("Invalid dcache line size: %u (must be power of 2)."), d);
 668     }
 669   target_dcache_invalidate ();
 670 }
 671
 672 static void
 673 set_dcache_command (const char *arg, int from_tty)
 674 {
 675   printf_unfiltered (
 676      "\"set dcache\" must be followed by the name of a subcommand.\n");
 677   help_list (dcache_set_list, "set dcache ", all_commands, gdb_stdout);
 678 }
 679
 680 static void
 681 show_dcache_command (const char *args, int from_tty)
 682 {
 683   cmd_show_list (dcache_show_list, from_tty, "");
 684 }
 685
 686 void
 687 _initialize_dcache (void)
 688 {
 689   add_setshow_boolean_cmd ("remotecache", class_support,
 690                            &dcache_enabled_p, _("\
 691 Set cache use for remote targets."), _("\
 692 Show cache use for remote targets."), _("\
 693 This used to enable the data cache for remote targets.  The cache\n\
 694 functionality is now controlled by the memory region system and the\n\
 695 \"stack-cache\" flag; \"remotecache\" now does nothing and\n\
 696 exists only for compatibility reasons."),
 697                            NULL,
 698                            show_dcache_enabled_p,
 699                            &setlist, &showlist);
 700
 701   add_info ("dcache", info_dcache_command,
 702             _("\
 703 Print information on the dcache performance.\n\
 704 Usage: info dcache [LINENUMBER]\n\
 705 With no arguments, this command prints the cache configuration and a\n\
 706 summary of each line in the cache.  With an argument, dump\"\n\
 707 the contents of the given line."));
 708
 709   add_prefix_cmd ("dcache", class_obscure, set_dcache_command, _("\
 710 Use this command to set number of lines in dcache and line-size."),
 711                   &dcache_set_list, "set dcache ", /*allow_unknown*/0, &setlist);
 712   add_prefix_cmd ("dcache", class_obscure, show_dcache_command, _("\
 713 Show dcachesettings."),
 714                   &dcache_show_list, "show dcache ", /*allow_unknown*/0, &showlist);
 715
 716   add_setshow_zuinteger_cmd ("line-size", class_obscure,
 717                              &dcache_line_size, _("\
 718 Set dcache line size in bytes (must be power of 2)."), _("\
 719 Show dcache line size."),
 720                              NULL,
 721                              set_dcache_line_size,
 722                              NULL,
 723                              &dcache_set_list, &dcache_show_list);
 724   add_setshow_zuinteger_cmd ("size", class_obscure,
 725                              &dcache_size, _("\
 726 Set number of dcache lines."), _("\
 727 Show number of dcache lines."),
 728                              NULL,
 729                              set_dcache_size,
 730                              NULL,
 731                              &dcache_set_list, &dcache_show_list);
 732 }