emacs/mps/code/arena.c

/* arena.c: ARENA ALLOCATION FEATURES
 *
 * $Id$
 * Copyright (c) 2001 Ravenbrook Limited.  See end of file for license.
 *
 * .sources: <design/arena/> is the main design document.  */

#include "tract.h"
#include "poolmv.h"
#include "mpm.h"
#include "cbs.h"
#include "bt.h"


SRCID(arena, "$Id$");


/* ArenaControlPool -- get the control pool */

#define ArenaControlPool(arena) MV2Pool(&(arena)->controlPoolStruct)


/* Forward declarations */

static void ArenaTrivCompact(Arena arena, Trace trace);


/* ArenaTrivDescribe -- produce trivial description of an arena */

static Res ArenaTrivDescribe(Arena arena, mps_lib_FILE *stream)
{
  if (!TESTT(Arena, arena)) return ResFAIL;
  if (stream == NULL) return ResFAIL;

  /* .describe.triv.never-called-from-subclass-method:
   * This Triv method seems to assume that it will never get called
   * from a subclass-method invoking ARENA_SUPERCLASS()->describe.
   * It assumes that it only gets called if the describe method has
   * not been subclassed.  (That's the only reason for printing the
   * "No class-specific description available" message).
   * This is bogus, but that's the status quo.  RHSK 2007-04-27.
   */
  /* .describe.triv.dont-upcall: Therefore (for now) the last 
   * subclass describe method should avoid invoking 
   * ARENA_SUPERCLASS()->describe.  RHSK 2007-04-27.
   */
  return WriteF(stream,
    "  No class-specific description available.\n", NULL);
}


/* AbstractArenaClass  -- The abstract arena class definition
 *
 * .null: Most abstract class methods are set to NULL.  See
 * <design/arena/#class.abstract.null>.  */

typedef ArenaClassStruct AbstractArenaClassStruct;

DEFINE_CLASS(AbstractArenaClass, class)
{
  INHERIT_CLASS(&class->protocol, ProtocolClass);
  class->name = "ABSARENA";
  class->size = 0;
  class->offset = 0;
  class->varargs = ArgTrivVarargs;
  class->init = NULL;
  class->finish = NULL;
  class->reserved = NULL;
  class->spareCommitExceeded = ArenaNoSpareCommitExceeded;
  class->extend = ArenaNoExtend;
  class->alloc = NULL;
  class->free = NULL;
  class->chunkInit = NULL;
  class->chunkFinish = NULL;
  class->compact = ArenaTrivCompact;
  class->describe = ArenaTrivDescribe;
  class->pagesMarkAllocated = NULL;
  class->sig = ArenaClassSig;
}


/* ArenaClassCheck -- check the consistency of an arena class */

Bool ArenaClassCheck(ArenaClass class)
{
  CHECKL(ProtocolClassCheck(&class->protocol));
  CHECKL(class->name != NULL); /* Should be <=6 char C identifier */
  CHECKL(class->size >= sizeof(ArenaStruct));
  /* Offset of generic Pool within class-specific instance cannot be */
  /* greater than the size of the class-specific portion of the */
  /* instance. */
  CHECKL(class->offset <= (size_t)(class->size - sizeof(ArenaStruct)));
  CHECKL(FUNCHECK(class->varargs));
  CHECKL(FUNCHECK(class->init));
  CHECKL(FUNCHECK(class->finish));
  CHECKL(FUNCHECK(class->reserved));
  CHECKL(FUNCHECK(class->spareCommitExceeded));
  CHECKL(FUNCHECK(class->extend));
  CHECKL(FUNCHECK(class->alloc));
  CHECKL(FUNCHECK(class->free));
  CHECKL(FUNCHECK(class->chunkInit));
  CHECKL(FUNCHECK(class->chunkFinish));
  CHECKL(FUNCHECK(class->compact));
  CHECKL(FUNCHECK(class->describe));
  CHECKL(FUNCHECK(class->pagesMarkAllocated));
  CHECKS(ArenaClass, class);
  return TRUE;
}


/* ArenaCheck -- check the arena */

Bool ArenaCheck(Arena arena)
{
  CHECKS(Arena, arena);
  CHECKD(Globals, ArenaGlobals(arena));
  CHECKD(ArenaClass, arena->class);

  CHECKL(BoolCheck(arena->poolReady));
  if (arena->poolReady) { /* <design/arena/#pool.ready> */
    CHECKD(CBS, &arena->freeCBS);
    CHECKD(MV, &arena->controlPoolStruct);
    CHECKD(Reservoir, &arena->reservoirStruct);
  }
  /* Can't check that limit>=size because we may call ArenaCheck */
  /* while the size is being adjusted. */

  CHECKL(arena->committed <= arena->commitLimit);
  CHECKL(arena->spareCommitted <= arena->committed);
  CHECKL(arena->spareCommitted <= arena->spareCommitLimit);

  CHECKL(ShiftCheck(arena->zoneShift));
  CHECKL(AlignCheck(arena->alignment));
  /* Tract allocation must be platform-aligned. */
  CHECKL(arena->alignment >= MPS_PF_ALIGN);
  /* Stripes can't be smaller than pages. */
  CHECKL(((Size)1 << arena->zoneShift) >= arena->alignment);

  if (arena->lastTract == NULL) {
    CHECKL(arena->lastTractBase == (Addr)0);
  } else {
    CHECKL(TractBase(arena->lastTract) == arena->lastTractBase);
  }

  if (arena->primary != NULL) {
    CHECKD(Chunk, arena->primary);
  }
  CHECKL(RingCheck(&arena->chunkRing));
  /* nothing to check for chunkSerial */
  CHECKD(ChunkCacheEntry, &arena->chunkCache);
  
  CHECKL(LocusCheck(arena));
  
  return TRUE;
}


/* ArenaInit -- initialize the generic part of the arena
 *
 * .init.caller: Unlike PoolInit, this is called by the class init
 * methods, not the generic Create.  This is because the class is
 * responsible for allocating the descriptor.  */

Res ArenaInit(Arena arena, ArenaClass class, Align alignment)
{
  Res res;

  /* We do not check the arena argument, because it's _supposed_ to */
  /* point to an uninitialized block of memory. */
  AVERT(ArenaClass, class);

  arena->class = class;

  arena->committed = (Size)0;
  /* commitLimit may be overridden by init (but probably not */
  /* as there's not much point) */
  arena->commitLimit = (Size)-1;
  arena->spareCommitted = (Size)0;
  arena->spareCommitLimit = ARENA_INIT_SPARE_COMMIT_LIMIT;
  arena->alignment = alignment;
  /* zoneShift is usually overridden by init */
  arena->zoneShift = ARENA_ZONESHIFT;
  arena->poolReady = FALSE;     /* <design/arena/#pool.ready> */
  arena->lastTract = NULL;
  arena->lastTractBase = NULL;

  arena->primary = NULL;
  RingInit(&arena->chunkRing);
  arena->chunkSerial = (Serial)0;
  ChunkCacheEntryInit(&arena->chunkCache);
  
  LocusInit(arena);
  
  res = GlobalsInit(ArenaGlobals(arena));
  if (res != ResOK)
    goto failGlobalsInit;

  arena->sig = ArenaSig;

  /* Initialise the freeCBS after the rest is initialised so that the CBS
     code can check the arena and pick up the alignment. */
  MPS_ARGS_BEGIN(cbsiArgs) {
    MPS_ARGS_ADD(cbsiArgs, MPS_KEY_CBS_EXTEND_BY, arena->alignment);
    MPS_ARGS_ADD(cbsiArgs, MFSExtendSelf, FALSE); /* FIXME: Explain why */
    MPS_ARGS_DONE(cbsiArgs);
    res = CBSInit(arena, &arena->freeCBS, arena, arena->alignment, TRUE, cbsiArgs);
  } MPS_ARGS_END(cbsiArgs);
  if (res != ResOK)
    goto failCBSInit;

  /* initialize the reservoir, <design/reservoir/> */
  res = ReservoirInit(&arena->reservoirStruct, arena);
  if (res != ResOK)
    goto failReservoirInit;

  AVERT(Arena, arena);
  return ResOK;

failReservoirInit:
  CBSFinish(&arena->freeCBS);
failCBSInit:
  GlobalsFinish(ArenaGlobals(arena));
failGlobalsInit:
  return res;
}


/* VM keys are defined here even though the code they apply to might
 * not be linked.  For example, MPS_KEY_VMW3_TOP_DOWN only applies to
 * vmw3.c.  The reason is that we want these keywords to be optional
 * even on the wrong platform, so that clients can write simple portable
 * code.  They should be free to pass MPS_KEY_VMW3_TOP_DOWN on other
 * platforms, knowing that it has no effect.  To do that, the key must
 * exist on all platforms. */

ARG_DEFINE_KEY(vmw3_top_down, Bool);


/* ArenaCreate -- create the arena and call initializers */

ARG_DEFINE_KEY(arena_size, Size);

Res ArenaCreate(Arena *arenaReturn, ArenaClass class, ArgList args)
{
  Arena arena;
  Res res;

  AVER(arenaReturn != NULL);
  AVERT(ArenaClass, class);
  AVER(ArgListCheck(args));

  /* We must initialise the event subsystem very early, because event logging
     will start as soon as anything interesting happens and expect to write
     to the EventLast pointers. */
  EventInit();

  /* Do initialization.  This will call ArenaInit (see .init.caller). */
  res = (*class->init)(&arena, class, args);
  if (res != ResOK)
    goto failInit;

  /* arena->alignment must have been set up by *class->init() */
  if (arena->alignment > ((Size)1 << arena->zoneShift)) {
    res = ResMEMORY; /* size was too small */
    goto failStripeSize;
  }

  res = ControlInit(arena);
  if (res != ResOK)
    goto failControlInit;

  res = GlobalsCompleteCreate(ArenaGlobals(arena));
  if (res != ResOK)
    goto failGlobalsCompleteCreate;

  AVERT(Arena, arena);
  *arenaReturn = arena;
  return ResOK;

failGlobalsCompleteCreate:
  ControlFinish(arena);
failControlInit:
failStripeSize:
  (*class->finish)(arena);
failInit:
  return res;
}


/* ArenaFinish -- finish the generic part of the arena
 *
 * .finish.caller: Unlike PoolFinish, this is called by the class finish
 * methods, not the generic Destroy.  This is because the class is
 * responsible for deallocating the descriptor.  */

void ArenaFinish(Arena arena)
{
  ReservoirFinish(ArenaReservoir(arena));
  arena->sig = SigInvalid;
  GlobalsFinish(ArenaGlobals(arena));
  LocusFinish(arena);
  RingFinish(&arena->chunkRing);
}


/* ArenaDestroy -- destroy the arena */

void ArenaDestroy(Arena arena)
{
  AVERT(Arena, arena);

  GlobalsPrepareToDestroy(ArenaGlobals(arena));

  /* Empty the reservoir - see <code/reserv.c#reservoir.finish> */
  ReservoirSetLimit(ArenaReservoir(arena), 0);

  arena->poolReady = FALSE;
  ControlFinish(arena);
  
  /* FIXME: The CBS MFS can't free via ArenaFree because that'll use the CBS,
     so manually get rid of all its tracts first.  Ought to reset the
     CBS tree first, so that there are no dangling pointers. */
  {
    Pool pool = &arena->freeCBS.blockPoolStruct.poolStruct;
    Tract tract = arena->freeCBS.blockPoolStruct.tractList;
    Size size = ArenaAlign(arena);
    while(tract != NULL) {
      Tract nextTract = (Tract)TractP(tract);   /* .tract.chain */
      (*arena->class->free)(TractBase(tract), size, pool);
      tract = nextTract;
    }
    arena->freeCBS.blockPoolStruct.tractList = NULL;
  }

  CBSFinish(&arena->freeCBS);

  /* Call class-specific finishing.  This will call ArenaFinish. */
  (*arena->class->finish)(arena);

  EventFinish();
}


/* ControlInit -- initialize the control pool */

Res ControlInit(Arena arena)
{
  Res res;

  AVERT(Arena, arena);
  MPS_ARGS_BEGIN(args) {
    MPS_ARGS_ADD(args, MPS_KEY_EXTEND_BY, CONTROL_EXTEND_BY);
    MPS_ARGS_DONE(args);
    res = PoolInit(&arena->controlPoolStruct.poolStruct, arena,
                   PoolClassMV(), args);
  } MPS_ARGS_END(args);
  if (res != ResOK)
    return res;
  arena->poolReady = TRUE;      /* <design/arena/#pool.ready> */
  return ResOK;
}


/* ControlFinish -- finish the control pool */

void ControlFinish(Arena arena)
{
  AVERT(Arena, arena);
  arena->poolReady = FALSE;
  PoolFinish(&arena->controlPoolStruct.poolStruct);
}


/* ArenaDescribe -- describe the arena */

Res ArenaDescribe(Arena arena, mps_lib_FILE *stream)
{
  Res res;
  Size reserved;

  if (!TESTT(Arena, arena)) return ResFAIL;
  if (stream == NULL) return ResFAIL;

  res = WriteF(stream, "Arena $P {\n", (WriteFP)arena,
               "  class $P (\"$S\")\n",
               (WriteFP)arena->class, arena->class->name,
               NULL);
  if (res != ResOK) return res;

  if (arena->poolReady) {
    res = WriteF(stream,
                 "  controlPool $P\n", (WriteFP)&arena->controlPoolStruct,
                 NULL);
    if (res != ResOK) return res;
  }

  /* Note: this Describe clause calls a function */
  reserved = ArenaReserved(arena);
  res = WriteF(stream,
               "  reserved         $W  <-- "
               "total size of address-space reserved\n",
               (WriteFW)reserved,
               NULL);
  if (res != ResOK) return res;

  res = WriteF(stream,
               "  committed        $W  <-- "
               "total bytes currently stored (in RAM or swap)\n",
               (WriteFW)arena->committed,
               "  commitLimit      $W\n", (WriteFW)arena->commitLimit,
               "  spareCommitted   $W\n", (WriteFW)arena->spareCommitted,
               "  spareCommitLimit $W\n", (WriteFW)arena->spareCommitLimit,
               "  zoneShift $U\n", (WriteFU)arena->zoneShift,
               "  alignment $W\n", (WriteFW)arena->alignment,
               NULL);
  if (res != ResOK) return res;

  res = WriteF(stream,
               "  droppedMessages $U$S\n", (WriteFU)arena->droppedMessages,
               (arena->droppedMessages == 0 ? "" : "  -- MESSAGES DROPPED!"),
               NULL);
  if (res != ResOK) return res;

  res = (*arena->class->describe)(arena, stream);
  if (res != ResOK) return res;

  /* Do not call GlobalsDescribe: it makes too much output, thanks.
   * RHSK 2007-04-27
   */
#if 0
  res = GlobalsDescribe(ArenaGlobals(arena), stream);
  if (res != ResOK) return res;
#endif

  res = WriteF(stream,
               "} Arena $P ($U)\n", (WriteFP)arena,
               (WriteFU)arena->serial,
               NULL);
  return res;
}


/* ArenaDescribeTracts -- describe all the tracts in the arena */

Res ArenaDescribeTracts(Arena arena, mps_lib_FILE *stream)
{
  Res res;
  Tract tract;
  Bool b;
  Addr oldLimit, base, limit;
  Size size;

  if (!TESTT(Arena, arena)) return ResFAIL;
  if (stream == NULL) return ResFAIL;

  b = TractFirst(&tract, arena);
  oldLimit = TractBase(tract);
  while (b) {
    base = TractBase(tract);
    limit = TractLimit(tract);
    size = ArenaAlign(arena);

    if (TractBase(tract) > oldLimit) {
      res = WriteF(stream,
                   "[$P, $P) $W $U   ---\n",
                   (WriteFP)oldLimit, (WriteFP)base,
                   (WriteFW)AddrOffset(oldLimit, base),
                   (WriteFU)AddrOffset(oldLimit, base),
                   NULL);
      if (res != ResOK) return res;
    }

    res = WriteF(stream,
                 "[$P, $P) $W $U   $P ($S)\n",
                 (WriteFP)base, (WriteFP)limit,
                 (WriteFW)size, (WriteFW)size,
                 (WriteFP)TractPool(tract),
                 (WriteFS)(TractPool(tract)->class->name),
                 NULL);
    if (res != ResOK) return res;
    b = TractNext(&tract, arena, TractBase(tract));
    oldLimit = limit;
  }
  return ResOK;
}


/* ControlAlloc -- allocate a small block directly from the control pool
 *
 * .arena.control-pool: Actually the block will be allocated from the
 * control pool, which is an MV pool embedded in the arena itself.
 *
 * .controlalloc.addr: In implementations where Addr is not compatible
 * with void* (<design/type/#addr.use>), ControlAlloc must take care of
 * allocating so that the block can be addressed with a void*.  */

Res ControlAlloc(void **baseReturn, Arena arena, size_t size,
                 Bool withReservoirPermit)
{
  Addr base;
  Res res;

  AVERT(Arena, arena);
  AVER(baseReturn != NULL);
  AVER(size > 0);
  AVER(BoolCheck(withReservoirPermit));
  AVER(arena->poolReady);

  res = PoolAlloc(&base, ArenaControlPool(arena), (Size)size,
                  withReservoirPermit);
  if (res != ResOK)
    return res;

  *baseReturn = (void *)base; /* see .controlalloc.addr */
  return ResOK;
}


/* ControlFree -- free a block allocated using ControlAlloc */

void ControlFree(Arena arena, void* base, size_t size)
{
  AVERT(Arena, arena);
  AVER(base != NULL);
  AVER(size > 0);
  AVER(arena->poolReady);

  PoolFree(ArenaControlPool(arena), (Addr)base, (Size)size);
}


/* ControlDescribe -- describe the arena's control pool */

Res ControlDescribe(Arena arena, mps_lib_FILE *stream)
{
  Res res;

  if (!TESTT(Arena, arena)) return ResFAIL;
  if (stream == NULL) return ResFAIL;

  res = PoolDescribe(ArenaControlPool(arena), stream);

  return res;
}


/* arenaAllocPage -- allocate one page from the arena
 *
 * This is a primitive allocator used to allocate pages for the arena CBS.
 * It is called rarely and can use a simple search.  It may not use the
 * CBS or any pool, because it is used as part of the bootstrap.
 */

static Res arenaAllocPageInChunk(Addr *baseReturn, Chunk chunk, Pool pool)
{
  Res res;
  Index basePageIndex, limitPageIndex;
  Arena arena;

  AVER(baseReturn != NULL);
  AVERT(Chunk, chunk);
  arena = ChunkArena(chunk);
  
  if (!BTFindShortResRange(&basePageIndex, &limitPageIndex,
                           chunk->allocTable,
                           chunk->allocBase, chunk->pages, 1))
    return ResRESOURCE;
  
  res = (*arena->class->pagesMarkAllocated)(arena, chunk,
                                            basePageIndex, 1,
                                            pool);
  if (res != ResOK)
    return res;
  
  *baseReturn = PageIndexBase(chunk, basePageIndex);
  return ResOK;
}

static Res arenaAllocPage(Addr *baseReturn, Arena arena, Pool pool)
{
  Res res;
  
  /* Favour the primary pool, because pages allocated this way aren't
     currently freed, and we don't want to prevent chunks being destroyed. */
  res = arenaAllocPageInChunk(baseReturn, arena->primary, pool);
  if (res != ResOK) {
    Ring node, next;
    RING_FOR(node, &arena->chunkRing, next) {
      Chunk chunk = RING_ELT(Chunk, chunkRing, node);
      if (chunk != arena->primary) {
        res = arenaAllocPageInChunk(baseReturn, chunk, pool);
        if (res == ResOK)
          break;
      }
    }
  }
  return res;
}


/* arenaFreeCBSInsert -- add block to free CBS, extending pool if necessary
 *
 * The arena's freeCBS can't get memory in the usual way because it is used
 * in the basic allocator, so we allocate pages specially.
 */

Res ArenaFreeCBSInsert(Arena arena, Addr base, Addr limit)
{
  Pool pool = &arena->freeCBS.blockPoolStruct.poolStruct;
  RangeStruct range;
  Res res;

  RangeInit(&range, base, limit);
  res = CBSInsert(&range, &arena->freeCBS, &range);
  if (res == ResLIMIT) { /* freeCBS MFS pool ran out of blocks */
    Addr pageBase;

    res = arenaAllocPage(&pageBase, arena, pool);
    if (res != ResOK)
      return res;

    MFSExtend(pool, pageBase, arena->alignment);

    /* Add the chunk's whole free area to the arena's CBS. */
    res = CBSInsert(&range, &arena->freeCBS, &range);
    AVER(res == ResOK); /* we just gave memory to the CBS */

    /* Exclude the page we specially allocated for the MFS from the CBS
       so that it doesn't get reallocated. */
    RangeInit(&range, pageBase, AddrAdd(pageBase, arena->alignment));
    res = CBSDelete(&range, &arena->freeCBS, &range);
    AVER(res == ResOK); /* we just gave memory to the CBS */
  }
  
  return ResOK;
}


/* arenaAllocFromCBS -- allocate memory using the free CBS
 *
 * The free CBS contains all the free address space we have in chunks,
 * so this is the primary method of allocation.
 */

static Res arenaAllocFromCBS(Tract *tractReturn, ZoneSet zones,
                             Size size, Pool pool)
{
  Arena arena;
  RangeStruct range, oldRange;
  Chunk chunk;
  Bool b;
  Index baseIndex;
  Count pages;
  Res res;

  AVER(tractReturn != NULL);
  /* ZoneSet is arbitrary */
  AVER(size > (Size)0);
  AVERT(Pool, pool);
  arena = PoolArena(pool);
  AVER(SizeIsAligned(size, arena->alignment));
  
  /* TODO: What about a range that crosses chunks?! Every chunk has
     some unallocated space at the beginning with page tables in it.
     This assumption needs documenting and asserting! */

  if (!CBSFindFirstInZones(&range, &oldRange, &arena->freeCBS, size,
                           arena, zones))
    return ResRESOURCE;
  
  b = CHUNK_OF_ADDR(&chunk, arena, range.base);
  AVER(b);
  AVER(RangeIsAligned(&range, ChunkPageSize(chunk)));
  baseIndex = INDEX_OF_ADDR(chunk, range.base);
  pages = ChunkSizeToPages(chunk, RangeSize(&range));
  res = (*arena->class->pagesMarkAllocated)(arena, chunk, baseIndex, pages, pool);
  if (res != ResOK)
    goto failMark;

  *tractReturn = PageTract(&chunk->pageTable[baseIndex]); /* FIXME: method for this? */
  return ResOK;

failMark:
   {
     Res insertRes = CBSInsert(&oldRange, &arena->freeCBS, &range);
     AVER(insertRes == ResOK); /* We only just deleted it. */
     /* If the insert does fail, we lose some address space permanently. */
   }
   return res;
}


/* arenaAllocPolicy -- arena allocation policy implementation
 *
 * This is the code responsible for making decisions about where to allocate
 * memory.  Avoid distributing code for doing this elsewhere, so that policy
 * can be maintained and adjusted.
 */

static Res arenaAllocPolicy(Tract *tractReturn, Arena arena, SegPref pref,
                            Size size, Pool pool)
{
  Res res;
  Tract tract;

  AVER(tractReturn != NULL);
  AVERT(SegPref, pref);
  AVER(size > (Size)0);
  AVERT(Pool, pool);

  /* Don't attempt to allocate if doing so would definitely exceed the
     commit limit. */
  if (arena->spareCommitted < size) {
    Size necessaryCommitIncrease = size - arena->spareCommitted;
    if (arena->committed + necessaryCommitIncrease > arena->commitLimit
        || arena->committed + necessaryCommitIncrease < arena->committed) {
      return ResCOMMIT_LIMIT;
    }
  }

  /* Plan A: allocate from the free CBS in the requested zones */
  /* FIXME: Takes no account of other zones fields */
  res = arenaAllocFromCBS(&tract, pref->zones, size, pool);
  if (res == ResOK) {
    *tractReturn = tract;
    return ResOK;
  }

  /* Plan B: extend the arena */
  /* FIXME: unimplemented! */
  return ResUNIMPL;
}


/* ArenaAlloc -- allocate some tracts from the arena */

Res ArenaAlloc(Addr *baseReturn, SegPref pref, Size size, Pool pool,
               Bool withReservoirPermit)
{
  Res res;
  Arena arena;
  Addr base;
  Tract tract;
  Reservoir reservoir;

  AVER(baseReturn != NULL);
  AVERT(SegPref, pref);
  AVER(size > (Size)0);
  AVERT(Pool, pool);
  AVER(BoolCheck(withReservoirPermit));

  arena = PoolArena(pool);
  AVERT(Arena, arena);
  AVER(SizeIsAligned(size, arena->alignment));
  reservoir = ArenaReservoir(arena);
  AVERT(Reservoir, reservoir);

  if (pool != ReservoirPool(reservoir)) {
    res = ReservoirEnsureFull(reservoir);
    if (res != ResOK) {
      AVER(ResIsAllocFailure(res));
      if (!withReservoirPermit)
        return res;
    }
  }

  res = arenaAllocPolicy(&tract, arena, pref, size, pool);
  if (res != ResOK) {
    if (withReservoirPermit) {
      Res resRes = ReservoirWithdraw(&base, &tract, reservoir, size, pool);
      if (resRes != ResOK)
        goto allocFail;
    } else
      goto allocFail;
  }
  
  base = TractBase(tract);

  /* cache the tract - <design/arena/#tract.cache> */
  arena->lastTract = tract;
  arena->lastTractBase = base;

  EVENT5(ArenaAlloc, arena, tract, base, size, pool);

  *baseReturn = base;
  return ResOK;

allocFail:
   EVENT3(ArenaAllocFail, arena, size, pool); /* TODO: Should have res? */
   return res;
}


/* ArenaFree -- free some tracts to the arena */

void ArenaFree(Addr base, Size size, Pool pool)
{
  Arena arena;
  Addr limit;
  Reservoir reservoir;
  Res res;
  Addr wholeBase;
  Size wholeSize;

  AVERT(Pool, pool);
  AVER(base != NULL);
  AVER(size > (Size)0);
  arena = PoolArena(pool);
  AVERT(Arena, arena);
  reservoir = ArenaReservoir(arena);
  AVERT(Reservoir, reservoir);
  AVER(AddrIsAligned(base, arena->alignment));
  AVER(SizeIsAligned(size, arena->alignment));

  /* uncache the tract if in range - <design/arena/#tract.uncache> */
  limit = AddrAdd(base, size);
  if ((arena->lastTractBase >= base) && (arena->lastTractBase < limit)) {
    arena->lastTract = NULL;
    arena->lastTractBase = (Addr)0;
  }
  
  wholeBase = base;
  wholeSize = size;

  if (pool != ReservoirPool(reservoir)) {
    res = ReservoirEnsureFull(reservoir);
    if (res != ResOK) {
      AVER(ResIsAllocFailure(res));
      /* FIXME: This appears to deposit the whole area into the reservoir
         no matter how big it is, possibly making the reservoir huge. */
      if (!ReservoirDeposit(reservoir, &base, &size))
        goto allDeposited;
    }
  }

  /* Just in case the shenanigans with the reservoir mucked this up. */
  AVER(limit == AddrAdd(base, size));

  /* Add the freed address space back into the freeCBS so that ArenaAlloc
     can find it again. */
  {
    RangeStruct rangeStruct;
    RangeInit(&rangeStruct, base, limit);
    res = CBSInsert(&rangeStruct, &arena->freeCBS, &rangeStruct);
    if (res != ResOK) {
      /* The CBS's MFS doesn't have enough space to describe the free memory.
         Give it some of the memory we're about to free and try again. */
      Tract tract = TractOfBaseAddr(arena, base);
      Pool mfs = &arena->freeCBS.blockPoolStruct.poolStruct;
      AVER(size >= ArenaAlign(arena));
      TractFinish(tract);
      TractInit(tract, mfs, base);
      MFSExtend(mfs, base, ArenaAlign(arena));
      base = AddrAdd(base, ArenaAlign(arena)); /* FIXME: = all chunk's pagesizes */
      size -= ArenaAlign(arena);
      if (size == 0)
        goto allTransferred;
      RangeInit(&rangeStruct, base, limit);
      res = CBSInsert(&rangeStruct, &arena->freeCBS, &rangeStruct);
      AVER(res == ResOK);
      /* If this fails, we lose some address space forever. */
    }
  }

  AVER(limit == AddrAdd(base, size));

  (*arena->class->free)(base, size, pool);

allTransferred:
allDeposited:
  EVENT3(ArenaFree, arena, wholeBase, wholeSize);
  return;
}


Size ArenaReserved(Arena arena)
{
  AVERT(Arena, arena);
  return (*arena->class->reserved)(arena);
}

Size ArenaCommitted(Arena arena)
{
  AVERT(Arena, arena);
  return arena->committed;
}

Size ArenaSpareCommitted(Arena arena)
{
  AVERT(Arena, arena);
  return arena->spareCommitted;
}

Size ArenaSpareCommitLimit(Arena arena)
{
  AVERT(Arena, arena);
  return arena->spareCommitLimit;
}

void ArenaSetSpareCommitLimit(Arena arena, Size limit)
{
  AVERT(Arena, arena);
  /* Can't check limit, as all possible values are allowed. */

  arena->spareCommitLimit = limit;
  if (arena->spareCommitLimit < arena->spareCommitted) {
    arena->class->spareCommitExceeded(arena);
  }

  EVENT2(SpareCommitLimitSet, arena, limit);
  return;
}

/* Used by arenas which don't use spare committed memory */
void ArenaNoSpareCommitExceeded(Arena arena)
{
  AVERT(Arena, arena);
  return;
}


Size ArenaCommitLimit(Arena arena)
{
  AVERT(Arena, arena);
  return arena->commitLimit;
}

Res ArenaSetCommitLimit(Arena arena, Size limit)
{
  Size committed;
  Res res;

  AVERT(Arena, arena);
  AVER(ArenaCommitted(arena) <= arena->commitLimit);

  committed = ArenaCommitted(arena);
  if (limit < committed) {
    /* Attempt to set the limit below current committed */
    if (limit >= committed - arena->spareCommitted) {
      /* could set the limit by flushing any spare committed memory */
      arena->class->spareCommitExceeded(arena);
      AVER(limit >= ArenaCommitted(arena));
      arena->commitLimit = limit;
      res = ResOK;
    } else {
      res = ResFAIL;
    }
  } else {
    arena->commitLimit = limit;
    res = ResOK;
  }
  EVENT3(CommitLimitSet, arena, limit, (res == ResOK));
  return res;
}


/* ArenaAvail -- return available memory in the arena */

Size ArenaAvail(Arena arena)
{
  Size sSwap;

  sSwap = ArenaReserved(arena);
  if (sSwap > arena->commitLimit)
    sSwap = arena->commitLimit;

  /* TODO: sSwap should take into account the amount of backing store
     available to supply the arena with memory.  This would be the amount
     available in the paging file, which is possibly the amount of free
     disk space in some circumstances.  We'd have to see whether we can get
     this information from the operating system.  It also depends on the
     arena class, of course. */

  return sSwap - arena->committed + arena->spareCommitted;
}


/* ArenaExtend -- Add a new chunk in the arena */

Res ArenaExtend(Arena arena, Addr base, Size size)
{
  Res res;

  AVERT(Arena, arena);
  AVER(base != (Addr)0);
  AVER(size > 0);

  res = (*arena->class->extend)(arena, base, size);
  if (res != ResOK)
    return res;

  EVENT3(ArenaExtend, arena, base, size);
  return ResOK;
}


/* ArenaNoExtend -- fail to extend the arena by a chunk */

Res ArenaNoExtend(Arena arena, Addr base, Size size)
{
  AVERT(Arena, arena);
  AVER(base != (Addr)0);
  AVER(size > (Size)0);

  NOTREACHED;
  return ResUNIMPL;
}


/* ArenaCompact -- respond (or not) to trace reclaim */

void ArenaCompact(Arena arena, Trace trace)
{
  AVERT(Arena, arena);
  AVERT(Trace, trace);
  (*arena->class->compact)(arena, trace);
}

static void ArenaTrivCompact(Arena arena, Trace trace)
{
  UNUSED(arena);
  UNUSED(trace);
  return;
}


/* Has Addr */

Bool ArenaHasAddr(Arena arena, Addr addr)
{
  Seg seg;

  AVERT(Arena, arena);
  return SegOfAddr(&seg, arena, addr);
}


/* ArenaAddrObject -- find client pointer to object containing addr
 * See job003589.
 */

Res ArenaAddrObject(Addr *pReturn, Arena arena, Addr addr)
{
  Seg seg;
  Pool pool;

  AVER(pReturn != NULL);
  AVERT(Arena, arena);
  
  if (!SegOfAddr(&seg, arena, addr)) {
    return ResFAIL;
  }
  pool = SegPool(seg);
  return PoolAddrObject(pReturn, pool, seg, addr);
}


/* C. COPYRIGHT AND LICENSE
 *
 * Copyright (C) 2001-2002 Ravenbrook Limited <http://www.ravenbrook.com/>.
 * All rights reserved.  This is an open source license.  Contact
 * Ravenbrook for commercial licensing options.
 * 
 * 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. Redistributions in any form must be accompanied by information on how
 * to obtain complete source code for this software and any accompanying
 * software that uses this software.  The source code must either be
 * included in the distribution or be available for no more than the cost
 * of distribution plus a nominal fee, and must be freely redistributable
 * under reasonable conditions.  For an executable file, complete source
 * code means the source code for all modules it contains. It does not
 * include source code for modules or files that typically accompany the
 * major components of the operating system on which the executable file
 * runs.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE, OR NON-INFRINGEMENT, ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS AND CONTRIBUTORS 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.
 */