MemorySegment.hpp

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/* Copyright (c) 2005-2009 Rexx Language Association. All rights reserved.    */
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/******************************************************************************/
/* REXX Kernel                                       RexxMemorysegment.hpp    */
/*                                                                            */
/* Primitive MemorySegment class definitions                                  */
/*                                                                            */
/******************************************************************************/
 
#ifndef Included_MemorySegment
#define Included_MemorySegment
 
#include "stddef.h"
#include "DeadObject.hpp"
#include "Interpreter.hpp"
 
#define MemorySegmentOverhead       (sizeof(MemorySegmentHeader))
#define MemorySegmentPoolOverhead   (sizeof(MemorySegmentPoolHeader))
 
#ifdef __REXX64__
// default size for a segment allocation, we go larger on 64-bit
#define SegmentSize (256*1024*2)
/* our threshold for moving to a larger block allocation scheme */
#define LargeBlockThreshold 8192
#else
/* default size for a segment allocation */
#define SegmentSize (256*1024)
/* our threshold for moving to a larger block allocation scheme */
#define LargeBlockThreshold 4096
#endif
/* Minimum size segment we'll allow */
#define MinimumSegmentSize (SegmentSize/2)
/* amount of usable space in a minimum sized segment */
#define MinimumSegmentDeadSpace (MinimumSegmentSize - MemorySegmentOverhead)
/* default size for a larger segment allocation */
#define LargeSegmentSize (SegmentSize * 4)
/* allocation available in a default segment */
#define SegmentDeadSpace (SegmentSize - MemorySegmentOverhead)
/* allocation request for the recovery segment */
#define RecoverSegmentSize ((SegmentSize/2) - MemorySegmentOverhead)
/* space available in a larger allocation. */
#define LargeSegmentDeadSpace (LargeSegmentSize - MemorySegmentOverhead)
 
#define InitialNormalSegmentSpace ((LargeSegmentSize * 8) - MemorySegmentOverhead)
 
#define LargestNormalSegmentSize (LargeObjectMinSize - (1024 * 1024)  - MemorySegmentOverhead)
 
 
/* Our threshold for deciding we're thrashing the garbage */
/* collector.  We'll always just extend memory if we're below this */
/* request threshold. */
#define MemoryThrashingThreshold 4
 
/* map an object length to an allocation deadpool.  NOTE:  this */
/* assumes the length has already been rounded to ObjectGrain! */
#define LengthToDeadPool(l) ((l)/ObjectGrain)
 
/* map a dead pool index to the size of blocks held in the pool */
#define DeadPoolToLength(d) ((d)*ObjectGrain)
/* index of first dead free chain.  We start with the previous */
/* chain, as older tokenized images can contain objects smaller */
/* than our minimum.  If these are garbage collected individually, */
/* we need a place to put them. */
#define FirstDeadPool (LengthToDeadPool(MinimumObjectSize) - 1)
/* The largest size element we'll keep in a subpool */
#define LargestSubpool 512
/* The index of the last subpool dead chain */
#define LastDeadPool LengthToDeadPool(LargestSubpool)
/* number of free chains (we index zero based, so we need to */
/* allocate one additional pool) */
#define DeadPools LastDeadPool + 1
 
/* the threshold to trigger expansion of the normal segment set. */
#define NormalMemoryExpansionThreshold .30
/* The point where we consider releasing segments */
#define NormalMemoryContractionThreshold .70
 
/* the sanity check point where we don't force automatic expansion */
/* of the normal heap */
#define MaxDeadObjectSpace 1000000
 
/* This rounds to segment sized chunks, not taking the overhead into account. */
inline size_t roundSegmentBoundary(size_t n) { return RXROUNDUP(n, SegmentSize); }
 
 
class RexxMemory;
 
/* A segment of heap memory. A MemorySegment will be associated */
/* with a particular MemorySegmentSet, which implements the */
/* suballocation rules. */
class MemorySegmentHeader {
 friend class MemorySegmentSet;
 friend class NormalSegmentSet;
 friend class LargeSegmentSet;
 friend class OldSegmentSet;
 friend class RexxMemory;
 
  protected:
   size_t segmentSize;                     /* size of the segment */
   size_t liveObjects;                     /* number of live objects in segment */
   MemorySegment *next;                    /* next segment in the chain */
   MemorySegment *previous;                /* previous segment in the chain */
};
 
/* A segment of heap memory. A MemorySegment will be associated */
/* with a particular MemorySegmentSet, which implements the */
/* suballocation rules. */
class MemorySegment : public MemorySegmentHeader {
 friend class MemorySegmentSet;
 friend class NormalSegmentSet;
 friend class LargeSegmentSet;
 friend class OldSegmentSet;
 friend class RexxMemory;
 
 public:
   inline void *operator new(size_t size, void *segment) { return segment; }
   inline void  operator delete(void *) { }
   inline void  operator delete(void *, void *) { }
 
   inline MemorySegment(size_t segSize) {
       segmentSize = segSize - sizeof(MemorySegmentHeader);
   }
   /* Following is a static constructor, called during RexxMemory */
   /* initialization */
   inline MemorySegment() {
       segmentSize = 0;
       /* Chain this segment to itself. */
       next = this;
       previous = this;
   }
 
   inline void insertAfter(MemorySegment *newSegment) {
       newSegment->next     = this->next;
       newSegment->previous = this;
       this->next->previous = newSegment;
       this->next           = newSegment;
   };
 
   inline void insertBefore(MemorySegment *newSegment) {
       newSegment->next     = this;
       newSegment->previous = this->previous;
       this->previous->next = newSegment;
       this->previous       = newSegment;
   };
 
   inline void remove() {
       this->next->previous = this->previous;
       this->previous->next = this->next;
   }
 
   inline void removeAll() {
       firstObject()->remove();
       remove();
   }
 
   inline bool isInSegment(RexxObject * object) {
       return (((char *)object >= segmentStart) && ((char *)object <= segmentStart + segmentSize));
   }
 
   inline DeadObject *createDeadObject() { return new ((void *)segmentStart) DeadObject(segmentSize); }
 
   inline DeadObject *firstObject() { return (DeadObject *)segmentStart; }
   inline void combine(MemorySegment *nextSegment) { segmentSize += nextSegment->segmentSize + MemorySegmentOverhead; }
   inline void shrink(size_t delta) { segmentSize -= delta; }
   inline bool isAdjacentTo(MemorySegment *seg) { return end() == (char *)seg; }
   inline bool isLastBlock(char *addr, size_t length) { return (addr + length) == end(); }
   inline bool isFirstBlock(char *addr) { return addr == start(); }
 
   inline size_t size() { return segmentSize; }
   inline size_t realSize() { return segmentSize + MemorySegmentOverhead; }
   inline char *start() { return segmentStart; }
   inline char *end() { return segmentStart + segmentSize; }
   inline bool isReal() { return segmentSize != 0; }
   inline bool isEmpty() { return liveObjects == 0; }
   void   dump(const char *owner, size_t counter, FILE *keyfile, FILE *dumpfile);
   DeadObject *lastDeadObject();
   DeadObject *firstDeadObject();
   void gatherObjectStats(MemoryStats *memStats, SegmentStats *stats);
   void markAllObjects();
 
  public:
   char segmentStart[8];                   /* start of the object data      */
};
 
 
 
 
/* A set of memory segments.  This manages the access to a pool of */
/* memory segments allocated for different uses by RexxMemory. */
/* This is a subclass of MemorySegment because the MemorySegmentSet */
/* object is also the anchor element for the segment chaining. */
class MemorySegmentSet {
    friend class RexxMemory;
 
  public:
      typedef enum { SET_UNINITIALIZED, SET_NORMAL, SET_LARGEBLOCK, SET_OLDSPACE } SegmentSetID;
        /* the memory segment mimic for anchoring the pool */
      MemorySegmentSet(RexxMemory *memObject, SegmentSetID id, const char *setName)  {
          /* Chain this segment to itself.     */
          owner = id;
          count = 0;
          /* keep the link back to the memory object that provides */
          /* us services. */
          this->memory = memObject;
          this->name = setName;
      }
        /* the default constructor */
      MemorySegmentSet()  {
          /* Chain this segment to itself.     */
          owner = SET_UNINITIALIZED;
          count = 0;
          /* The link to the memory object will need to be established later */
          memory = NULL;
      }
 
      virtual ~MemorySegmentSet() { ; }
      inline void *operator new(size_t size, void *segment) { return segment; }
      inline void  operator delete(void * size) { }
      inline void  operator delete(void * size, void *segment) { }
 
      /* Following is a static constructor, called during */
      /* RexxMemeory initialization */
 
      inline void removeSegment(MemorySegment *segment) {
          /* remove both the segment, and any blocks on the dead */
          /* chains. */
          segment->remove();
          count--;
      }
 
      inline void removeSegmentAndStorage(MemorySegment *segment) {
          /* remove both the segment, and any blocks on the dead */
          /* chains. */
          segment->removeAll();
          count--;
      }
 
      inline void add(MemorySegment *segment) {
          anchor.insertBefore(segment);
          count++;
      }
 
      inline MemorySegment *first() {
          if (anchor.next->isReal()) {
              return anchor.next;
          }
          else {
              return NULL;
          }
      }
 
      inline MemorySegment *next(MemorySegment *segment) {
          if (segment->next->isReal()) {
              return segment->next;
          }
          else {
              return NULL;
          }
      }
 
      inline bool isInSegmentSet(RexxObject *object) {
          MemorySegment *segment = first();
          while (segment != NULL) {
              if (segment->isInSegment(object)) {
                  return true;
              }
              segment = next(segment);
          }
          return false;
      }
 
 
      void dumpSegments(FILE *keyfile, FILE *dumpfile);
      void addSegment(MemorySegment *segment, bool createDeadObject = 1);
      void sweep();
      inline bool is(SegmentSetID id) { return owner == id; }
      void gatherStats(MemoryStats *memStats, SegmentStats *stats);
 
 
      virtual void   dumpMemoryProfile(FILE *outfile);
      virtual DeadObject *donateObject(size_t allocationLength);
      virtual MemorySegment *donateSegment(size_t allocationLength);
 
  protected:
 
      virtual void collectEmptySegments();
      virtual void addDeadObject(DeadObject *object);
      virtual void addDeadObject(char *object, size_t length);
      RexxObject *splitDeadObject(DeadObject *object, size_t allocationLength, size_t splitMinimum);
      void insertSegment(MemorySegment *segment);
      MemorySegment *findEmptySegment(size_t allocationLength);
      MemorySegment *splitSegment(size_t allocationLength);
      void mergeSegments(size_t allocationLength);
      void combineEmptySegments(MemorySegment *front, MemorySegment *back);
      virtual size_t suggestMemoryExpansion();
      virtual size_t suggestMemoryContraction();
      virtual void prepareForSweep();
      virtual void completeSweepOperation();
      MemorySegment *largestActiveSegment();
      MemorySegment *largestEmptySegment();
      void adjustMemorySize();
      void releaseEmptySegments(size_t releaseSize);
      void releaseSegment(MemorySegment *segment);
      bool newSegment(size_t requestLength, size_t minimumLength);
 
      virtual MemorySegment *allocateSegment(size_t requestLength, size_t minimumLength);
      inline float freeMemoryPercentage() {return (float)deadObjectBytes/(float)(deadObjectBytes + liveObjectBytes);  }
      inline size_t totalFreeMemory() { return liveObjectBytes + deadObjectBytes; }
      /* This rounds a size into an even segment multiple, taking the */
      /* segment overhead into account. */
      inline size_t calculateSegmentAllocation(size_t n) {
          size_t size = roundSegmentBoundary(n) - MemorySegmentOverhead;
          /* this could be true if our size is larger than can fit into a */
          /* segment once the overhead is considered.  If we can't fit, */
          /* we go over by a segment. */
          if (size < n)  {
              size += SegmentSize;
          }
          return size;
      }
      void addSegments(size_t requiredSpace);
      MemorySegment *getSegment(size_t requestLength, size_t minimumLength);
      void activateEmptySegments();
 
#ifndef CHECKOREFS
      inline void validateObject(size_t bytes) {};
#else
      void validateObject(size_t bytes); // Must be moved to .cpp file because compile error with Interpreter::logicError
#endif
 
 
 
    MemorySegment anchor;                 /* the anchor for our active segment chain */
    MemorySegment emptySegments;          /* our empty segment chain (used for reserves) */
    size_t  count;                        /* the number of elements in the pool */
    size_t  liveObjectBytes;              /* bytes allocation to live objects */
    size_t  deadObjectBytes;              /* bytes consumed by dead objects */
    SegmentSetID owner;                   /* the owner of this segment */
    const char  *name;                    /* character identifier for debugging/profiling */
    RexxMemory  *memory;                  /* the hosting memory object */
};
 
 
class NormalSegmentSet : public MemorySegmentSet
{
  public:
 
    /* the default constructor */
    NormalSegmentSet()  { ; }
    NormalSegmentSet(RexxMemory *memory);
    virtual ~NormalSegmentSet() { ; }
    virtual void   dumpMemoryProfile(FILE *outfile);
    inline  RexxObject *allocateObject(size_t allocationLength)
    {
        DeadObject *newObject;
        size_t targetPool;
        size_t realLength;
 
        /* Calculate the dead chain.  Note that if this is larger than */
        /* the largest subpool, the for() loop test below will fail, */
        /* causing this to drop down to the large block allocation */
        /* logic.  This eliminates an additional check against the */
        /* large size. */
        targetPool = LengthToDeadPool(allocationLength);
 
        if (targetPool < DeadPools) {
 
            /* pick up the last successful one */
            size_t currentDead = lastUsedSubpool[targetPool];
            /* loop through the small pool chains looking for a block. */
            /* We only go up to the largest blocks as a last resort to */
            /* reduce the fragmentation. */
            while (currentDead < DeadPools) {
                /* See if the chain has an object.  Once we get an */
                /* object, we return this directly.  We accept over */
                /* allocations when then come from the subpool chain. */
                /* Since this is such a heavily hit path, we don't want */
                /* to absorb the overhead of attempting to split the */
                /* blocks.  For the majority of over allocations, we */
                /* can't split anyway.  When we do split, the result is */
                /* a very small fragment. */
                newObject = subpools[currentDead].getFirstSingle();
                if (newObject != OREF_NULL) {
                    /* Record the success.  Next time around, */
                    /* allocations will come directly here. */
                    lastUsedSubpool[targetPool] = currentDead;
                    /* we have a block.  Now see if we got this from a */
                    /* higher level chain and have enough room to */
                    /* subdivide into a small block. */
                    /* Convert this from a dead object into a real one of the */
                    /* given size. */
                    return (RexxObject *)newObject;
                }
 
                currentDead++;
 
                while (currentDead < DeadPools)
                {
                    if (lastUsedSubpool[currentDead] < DeadPools)
                    {
                        // this pool might be redirected already, so
                        // pick up the index of where it's redirected to.
                        currentDead = lastUsedSubpool[currentDead];
                        lastUsedSubpool[targetPool] = currentDead;
                        break;
                    }
                    currentDead++;
                }
            }
            /* we've gone all the way to the end without finding */
            /* anything.  Cause the next allocation to skip directly to */
            /* the large chain. */
            lastUsedSubpool[targetPool] = DeadPools;
        }
        /* Nope, go through the LARGEDEAD object looking for the 1st */
        /* one we can use either our object is too big for all the */
        /* small chains, or the small chains are depleted.... */
        /* Go through the LARGEDEAD object looking for the 1st */
        /* one we can use either our object is too big for all the */
        /* small chains, or the small chains are depleted.... */
        newObject = largeDead.findFit(allocationLength, &realLength);
        if (newObject != NULL) {         /* did we find an object?            */
            size_t deadLength = realLength - allocationLength;
            /* remainder too small or this is a very large request */
            /* is the remainder two small to reuse? */
            if (deadLength < MinimumObjectSize) {
                /* Convert this from a dead object into a real one of the */
                /* given size. */
                return (RexxObject *)newObject;
            }
            else {
                /* potentially split this object into a smaller unit so we */
                /* can reuse the remainder. */
                return splitNormalDeadObject(newObject, allocationLength, deadLength);
            }
        }
        return OREF_NULL;
    }
 
            RexxObject *handleAllocationFailure(size_t allocationLength);
    virtual DeadObject *donateObject(size_t allocationLength);
    void    getInitialSet();
    virtual size_t suggestMemoryExpansion();
    virtual size_t suggestMemoryContraction();
 
  protected:
    virtual void addDeadObject(DeadObject *object);
    virtual void addDeadObject(char *object, size_t length);
    virtual void prepareForSweep();
            void completeSweepOperation();
 
  private:
 
    inline size_t mapLengthToDeadPool(size_t length) { return length/ObjectGrain; }
    RexxObject *findLargeDeadObject(size_t allocationLength);
    inline size_t recommendedMemorySize() { return (size_t)((float)liveObjectBytes/(1.0 - NormalMemoryExpansionThreshold)); }
    inline size_t recommendedMaximumMemorySize() { return (size_t)((float)liveObjectBytes/(1.0 - NormalMemoryContractionThreshold)); }
    void checkObjectOverlap(DeadObject *obj);
    RexxObject *findObject(size_t allocationLength);
    inline RexxObject *splitNormalDeadObject(DeadObject *object, size_t allocationLength, size_t deadLength)
    {
        /* we need to keep all of these sizes as ObjectGrain multiples, */
        /* so round it down...the allocation will get all of the extra. */
        /* deadLength = rounddown(deadLength, ObjectGrain);
           allocationLength is rounded, deadLength might be
           an ungrained object size from old tokenized format */
 
        /* Yes, so pull new object out of the front of the dead */
        /* object, adjust the size of the Dead object.  We want */
        /* to use the front rather than the back so that if we */
        /* hit the need to split a segment because of low memory */
        /* conditions, we increase the probability that we'll be */
        /* able to use the end of the segment. */
        DeadObject *largeObject = (DeadObject *)(((char *)object) + allocationLength);
        /* if the length is larger than the biggest subpool we */
        /* maintain, we add this to the large block list. */
        if (deadLength > LargestSubpool) {
              /* ideally, we'd like to add this sorted by size, but */
              /* this is called so frequently, attempting to sort */
              /* degrades performance by about 10%. */
              largeDead.add(new (largeObject) DeadObject(deadLength));
        }
        else {
            /* calculate the dead chain          */
            /* and add that to the appropriate chain */
            size_t deadChain = LengthToDeadPool(deadLength);
            subpools[deadChain].addSingle(new (largeObject) DeadObject(deadLength));
            /* we can mark this subpool as having items again */
            lastUsedSubpool[deadChain] = deadChain;
        }
        /* Convert this from a dead object into a real one of the */
        /* given size. */
        ((RexxObject *)object)->setObjectSize(allocationLength);
        return (RexxObject *)object;
    }
 
    DeadObjectPool largeDead;             /* the set of large dead objects */
    DeadObjectPool subpools[DeadPools];   /* our set of allocation subpools */
    size_t lastUsedSubpool[DeadPools + 1];/* a look-aside index to tell us what pool to use for a given size */
    MemorySegment *recoverSegment;        /* our last-ditch memory segment */
};
 
 
class LargeSegmentSet : public MemorySegmentSet
{
  public:
 
    /* the default constructor */
    LargeSegmentSet()  { ; }
    LargeSegmentSet(RexxMemory *memory);
    virtual ~LargeSegmentSet() { ; }
    virtual void   dumpMemoryProfile(FILE *outfile);
    RexxObject *handleAllocationFailure(size_t allocationLength);
    inline RexxObject *allocateObject(size_t allocationLength)
        {
          DeadObject *largeObject;
 
          /* go through the LARGEDEAD object looking for the 1st one we can */
          /* use either our object is too big for all the small chains, or */
          /* the small chain are depleted.... */
          largeObject = deadCache.findBestFit(allocationLength);
          /* did we find an object?            */
          if (largeObject != NULL) {
              /* remember the successful request */
              requests++;
              /* split and prepare this object for use */
              return splitDeadObject(largeObject, allocationLength, LargeAllocationUnit);
          }
          return OREF_NULL;                    /* we couldn't get this              */
        }
 
    virtual DeadObject *donateObject(size_t allocationLength);
 
protected:
 
    virtual void addDeadObject(DeadObject *object);
    virtual void addDeadObject(char *object, size_t length);
    virtual MemorySegment *allocateSegment(size_t requestLength, size_t minimumLength);
    void expandOrCollect(size_t allocationLength);
    void expandSegmentSet(size_t allocationLength);
    virtual void prepareForSweep();
            void completeSweepOperation();
 
  private:
 
    RexxObject *findObject(size_t allocationLength);
 
    DeadObjectPool deadCache;             /* the set of large dead objects */
    size_t         requests;              /* requests since last gc cycle. */
    size_t         smallestObject;        // the smallest object in the set
    size_t         largestObject;         // the largest object in the set
};
 
 
class OldSpaceSegmentSet : public MemorySegmentSet
{
  public:
 
    /* the default constructor */
    OldSpaceSegmentSet()  { ; }
    OldSpaceSegmentSet(RexxMemory *memory);
    virtual ~OldSpaceSegmentSet() { ; }
            RexxObject *allocateObject(size_t allocationLength);
 
    void markOldSpaceObjects();
 
  protected:
    virtual void addDeadObject(DeadObject *object);
    virtual void addDeadObject(char *object, size_t length);
    RexxObject *findObject(size_t allocationLength);
 
  private:
    DeadObjectPool deadCache;             /* the set of objects on the old dead chain */
};
 
#endif