aset.c File Reference

#include "postgres.h"
#include "port/pg_bitutils.h"
#include "utils/memdebug.h"
#include "utils/memutils.h"

Include dependency graph for aset.c:

Go to the source code of this file.

Data Structures
struct	AllocSetContext
struct	AllocBlockData
struct	AllocChunkData
struct	AllocSetFreeList

Macros
#define	ALLOC_MINBITS   3 /* smallest chunk size is 8 bytes */
#define	ALLOCSET_NUM_FREELISTS   11
#define	ALLOC_CHUNK_LIMIT   (1 << (ALLOCSET_NUM_FREELISTS-1+ALLOC_MINBITS))
#define	ALLOC_CHUNK_FRACTION   4
#define	ALLOC_BLOCKHDRSZ   MAXALIGN(sizeof(AllocBlockData))
#define	ALLOC_CHUNKHDRSZ   sizeof(struct AllocChunkData)
#define	ALLOCCHUNK_RAWSIZE   (SIZEOF_SIZE_T + SIZEOF_VOID_P)
#define	ALLOCCHUNK_PRIVATE_LEN   offsetof(AllocChunkData, aset)
#define	AllocPointerIsValid(pointer)   PointerIsValid(pointer)
#define	AllocSetIsValid(set)   PointerIsValid(set)
#define	AllocPointerGetChunk(ptr)   ((AllocChunk)(((char *)(ptr)) - ALLOC_CHUNKHDRSZ))
#define	AllocChunkGetPointer(chk)   ((AllocPointer)(((char *)(chk)) + ALLOC_CHUNKHDRSZ))
#define	MAX_FREE_CONTEXTS   100 /* arbitrary limit on freelist length */

Typedefs
typedef struct AllocBlockData *	AllocBlock
typedef struct AllocChunkData *	AllocChunk
typedef void *	AllocPointer
typedef struct AllocSetContext	AllocSetContext
typedef AllocSetContext *	AllocSet
typedef struct AllocBlockData	AllocBlockData
typedef struct AllocChunkData	AllocChunkData
typedef struct AllocSetFreeList	AllocSetFreeList

Functions
static void *	AllocSetAlloc (MemoryContext context, Size size)
static void	AllocSetFree (MemoryContext context, void *pointer)
static void *	AllocSetRealloc (MemoryContext context, void *pointer, Size size)
static void	AllocSetReset (MemoryContext context)
static void	AllocSetDelete (MemoryContext context)
static Size	AllocSetGetChunkSpace (MemoryContext context, void *pointer)
static bool	AllocSetIsEmpty (MemoryContext context)
static void	AllocSetStats (MemoryContext context, MemoryStatsPrintFunc printfunc, void *passthru, MemoryContextCounters *totals)
static int	AllocSetFreeIndex (Size size)
MemoryContext	AllocSetContextCreateInternal (MemoryContext parent, const char *name, Size minContextSize, Size initBlockSize, Size maxBlockSize)

Variables
static AllocSetFreeList	context_freelists [2]
static const MemoryContextMethods	AllocSetMethods

Macro Definition Documentation

ALLOC_BLOCKHDRSZ

#define ALLOC_BLOCKHDRSZ   MAXALIGN(sizeof(AllocBlockData))

Definition at line 100 of file aset.c.

Referenced by AllocSetAlloc(), AllocSetContextCreateInternal(), AllocSetFree(), AllocSetRealloc(), AllocSetReset(), and AllocSetStats().

ALLOC_CHUNK_FRACTION

#define ALLOC_CHUNK_FRACTION   4

Definition at line 83 of file aset.c.

Referenced by AllocSetContextCreateInternal().

ALLOC_CHUNK_LIMIT

#define ALLOC_CHUNK_LIMIT   (1 << (ALLOCSET_NUM_FREELISTS-1+ALLOC_MINBITS))

Definition at line 81 of file aset.c.

Referenced by AllocSetContextCreateInternal(), and AllocSetFreeIndex().

ALLOC_CHUNKHDRSZ

#define ALLOC_CHUNKHDRSZ   sizeof(struct AllocChunkData)

Definition at line 101 of file aset.c.

Referenced by AllocSetAlloc(), AllocSetContextCreateInternal(), AllocSetFree(), AllocSetGetChunkSpace(), AllocSetRealloc(), and AllocSetStats().

ALLOC_MINBITS

#define ALLOC_MINBITS   3 /* smallest chunk size is 8 bytes */

Definition at line 79 of file aset.c.

Referenced by AllocSetAlloc(), AllocSetFreeIndex(), and AllocSetStats().

ALLOCCHUNK_PRIVATE_LEN

#define ALLOCCHUNK_PRIVATE_LEN   offsetof(AllocChunkData, aset)

Definition at line 202 of file aset.c.

Referenced by AllocSetAlloc(), AllocSetFree(), AllocSetGetChunkSpace(), AllocSetRealloc(), and AllocSetStats().

ALLOCCHUNK_RAWSIZE

#define ALLOCCHUNK_RAWSIZE   (SIZEOF_SIZE_T + SIZEOF_VOID_P)

Definition at line 183 of file aset.c.

AllocChunkGetPointer

#define AllocChunkGetPointer

(

chk

)

((AllocPointer)(((char *)(chk)) + ALLOC_CHUNKHDRSZ))

Definition at line 218 of file aset.c.

Referenced by AllocSetAlloc(), and AllocSetRealloc().

AllocPointerGetChunk

#define AllocPointerGetChunk

(

ptr

)

((AllocChunk)(((char *)(ptr)) - ALLOC_CHUNKHDRSZ))

Definition at line 216 of file aset.c.

Referenced by AllocSetFree(), AllocSetGetChunkSpace(), and AllocSetRealloc().

AllocPointerIsValid

#define AllocPointerIsValid

(

pointer

)

PointerIsValid(pointer)

Definition at line 208 of file aset.c.

ALLOCSET_NUM_FREELISTS

#define ALLOCSET_NUM_FREELISTS   11

Definition at line 80 of file aset.c.

Referenced by AllocSetFreeIndex(), and AllocSetStats().

AllocSetIsValid

#define AllocSetIsValid

(

set

)

PointerIsValid(set)

Definition at line 214 of file aset.c.

Referenced by AllocSetAlloc(), AllocSetDelete(), and AllocSetReset().

MAX_FREE_CONTEXTS

#define MAX_FREE_CONTEXTS   100 /* arbitrary limit on freelist length */

Definition at line 244 of file aset.c.

Referenced by AllocSetDelete().

Typedef Documentation

AllocBlock

typedef struct AllocBlockData* AllocBlock

Definition at line 103 of file aset.c.

AllocBlockData

typedef struct AllocBlockData AllocBlockData

AllocChunk

typedef struct AllocChunkData* AllocChunk

Definition at line 104 of file aset.c.

AllocChunkData

typedef struct AllocChunkData AllocChunkData

AllocPointer

typedef void* AllocPointer

Definition at line 110 of file aset.c.

AllocSet

typedef AllocSetContext* AllocSet

Definition at line 137 of file aset.c.

AllocSetContext

typedef struct AllocSetContext AllocSetContext

AllocSetFreeList

typedef struct AllocSetFreeList AllocSetFreeList

Function Documentation

AllocSetAlloc()

static void * AllocSetAlloc ( MemoryContext  context, Size  size  )

static

Definition at line 720 of file aset.c.

References ALLOC_BLOCKHDRSZ, ALLOC_CHUNKHDRSZ, ALLOC_MINBITS, ALLOCCHUNK_PRIVATE_LEN, AllocChunkGetPointer, AllocSetFreeIndex(), AllocSetIsValid, AllocBlockData::aset, AllocChunkData::aset, Assert, AssertArg, AllocBlockData::endptr, AllocBlockData::freeptr, malloc, MAXALIGN, MemoryContextData::mem_allocated, AllocBlockData::next, AllocBlockData::prev, AllocChunkData::size, VALGRIND_MAKE_MEM_NOACCESS, and VALGRIND_MAKE_MEM_UNDEFINED.

Referenced by AllocSetRealloc().

{
    AllocSet    set = (AllocSet) context;
    AllocBlock  block;
    AllocChunk  chunk;
    int         fidx;
    Size        chunk_size;
    Size        blksize;

    AssertArg(AllocSetIsValid(set));

    /*
     * If requested size exceeds maximum for chunks, allocate an entire block
     * for this request.
     */
    if (size > set->allocChunkLimit)
    {
        chunk_size = MAXALIGN(size);
        blksize = chunk_size + ALLOC_BLOCKHDRSZ + ALLOC_CHUNKHDRSZ;
        block = (AllocBlock) malloc(blksize);
        if (block == NULL)
            return NULL;

        context->mem_allocated += blksize;

        block->aset = set;
        block->freeptr = block->endptr = ((char *) block) + blksize;

        chunk = (AllocChunk) (((char *) block) + ALLOC_BLOCKHDRSZ);
        chunk->aset = set;
        chunk->size = chunk_size;
#ifdef MEMORY_CONTEXT_CHECKING
        chunk->requested_size = size;
        /* set mark to catch clobber of "unused" space */
        if (size < chunk_size)
            set_sentinel(AllocChunkGetPointer(chunk), size);
#endif
#ifdef RANDOMIZE_ALLOCATED_MEMORY
        /* fill the allocated space with junk */
        randomize_mem((char *) AllocChunkGetPointer(chunk), size);
#endif

        /*
         * Stick the new block underneath the active allocation block, if any,
         * so that we don't lose the use of the space remaining therein.
         */
        if (set->blocks != NULL)
        {
            block->prev = set->blocks;
            block->next = set->blocks->next;
            if (block->next)
                block->next->prev = block;
            set->blocks->next = block;
        }
        else
        {
            block->prev = NULL;
            block->next = NULL;
            set->blocks = block;
        }

        /* Ensure any padding bytes are marked NOACCESS. */
        VALGRIND_MAKE_MEM_NOACCESS((char *) AllocChunkGetPointer(chunk) + size,
                                   chunk_size - size);

        /* Disallow external access to private part of chunk header. */
        VALGRIND_MAKE_MEM_NOACCESS(chunk, ALLOCCHUNK_PRIVATE_LEN);

        return AllocChunkGetPointer(chunk);
    }

    /*
     * Request is small enough to be treated as a chunk.  Look in the
     * corresponding free list to see if there is a free chunk we could reuse.
     * If one is found, remove it from the free list, make it again a member
     * of the alloc set and return its data address.
     */
    fidx = AllocSetFreeIndex(size);
    chunk = set->freelist[fidx];
    if (chunk != NULL)
    {
        Assert(chunk->size >= size);

        set->freelist[fidx] = (AllocChunk) chunk->aset;

        chunk->aset = (void *) set;

#ifdef MEMORY_CONTEXT_CHECKING
        chunk->requested_size = size;
        /* set mark to catch clobber of "unused" space */
        if (size < chunk->size)
            set_sentinel(AllocChunkGetPointer(chunk), size);
#endif
#ifdef RANDOMIZE_ALLOCATED_MEMORY
        /* fill the allocated space with junk */
        randomize_mem((char *) AllocChunkGetPointer(chunk), size);
#endif

        /* Ensure any padding bytes are marked NOACCESS. */
        VALGRIND_MAKE_MEM_NOACCESS((char *) AllocChunkGetPointer(chunk) + size,
                                   chunk->size - size);

        /* Disallow external access to private part of chunk header. */
        VALGRIND_MAKE_MEM_NOACCESS(chunk, ALLOCCHUNK_PRIVATE_LEN);

        return AllocChunkGetPointer(chunk);
    }

    /*
     * Choose the actual chunk size to allocate.
     */
    chunk_size = (1 << ALLOC_MINBITS) << fidx;
    Assert(chunk_size >= size);

    /*
     * If there is enough room in the active allocation block, we will put the
     * chunk into that block.  Else must start a new one.
     */
    if ((block = set->blocks) != NULL)
    {
        Size        availspace = block->endptr - block->freeptr;

        if (availspace < (chunk_size + ALLOC_CHUNKHDRSZ))
        {
            /*
             * The existing active (top) block does not have enough room for
             * the requested allocation, but it might still have a useful
             * amount of space in it.  Once we push it down in the block list,
             * we'll never try to allocate more space from it. So, before we
             * do that, carve up its free space into chunks that we can put on
             * the set's freelists.
             *
             * Because we can only get here when there's less than
             * ALLOC_CHUNK_LIMIT left in the block, this loop cannot iterate
             * more than ALLOCSET_NUM_FREELISTS-1 times.
             */
            while (availspace >= ((1 << ALLOC_MINBITS) + ALLOC_CHUNKHDRSZ))
            {
                Size        availchunk = availspace - ALLOC_CHUNKHDRSZ;
                int         a_fidx = AllocSetFreeIndex(availchunk);

                /*
                 * In most cases, we'll get back the index of the next larger
                 * freelist than the one we need to put this chunk on.  The
                 * exception is when availchunk is exactly a power of 2.
                 */
                if (availchunk != ((Size) 1 << (a_fidx + ALLOC_MINBITS)))
                {
                    a_fidx--;
                    Assert(a_fidx >= 0);
                    availchunk = ((Size) 1 << (a_fidx + ALLOC_MINBITS));
                }

                chunk = (AllocChunk) (block->freeptr);

                /* Prepare to initialize the chunk header. */
                VALGRIND_MAKE_MEM_UNDEFINED(chunk, ALLOC_CHUNKHDRSZ);

                block->freeptr += (availchunk + ALLOC_CHUNKHDRSZ);
                availspace -= (availchunk + ALLOC_CHUNKHDRSZ);

                chunk->size = availchunk;
#ifdef MEMORY_CONTEXT_CHECKING
                chunk->requested_size = 0;  /* mark it free */
#endif
                chunk->aset = (void *) set->freelist[a_fidx];
                set->freelist[a_fidx] = chunk;
            }

            /* Mark that we need to create a new block */
            block = NULL;
        }
    }

    /*
     * Time to create a new regular (multi-chunk) block?
     */
    if (block == NULL)
    {
        Size        required_size;

        /*
         * The first such block has size initBlockSize, and we double the
         * space in each succeeding block, but not more than maxBlockSize.
         */
        blksize = set->nextBlockSize;
        set->nextBlockSize <<= 1;
        if (set->nextBlockSize > set->maxBlockSize)
            set->nextBlockSize = set->maxBlockSize;

        /*
         * If initBlockSize is less than ALLOC_CHUNK_LIMIT, we could need more
         * space... but try to keep it a power of 2.
         */
        required_size = chunk_size + ALLOC_BLOCKHDRSZ + ALLOC_CHUNKHDRSZ;
        while (blksize < required_size)
            blksize <<= 1;

        /* Try to allocate it */
        block = (AllocBlock) malloc(blksize);

        /*
         * We could be asking for pretty big blocks here, so cope if malloc
         * fails.  But give up if there's less than 1 MB or so available...
         */
        while (block == NULL && blksize > 1024 * 1024)
        {
            blksize >>= 1;
            if (blksize < required_size)
                break;
            block = (AllocBlock) malloc(blksize);
        }

        if (block == NULL)
            return NULL;

        context->mem_allocated += blksize;

        block->aset = set;
        block->freeptr = ((char *) block) + ALLOC_BLOCKHDRSZ;
        block->endptr = ((char *) block) + blksize;

        /* Mark unallocated space NOACCESS. */
        VALGRIND_MAKE_MEM_NOACCESS(block->freeptr,
                                   blksize - ALLOC_BLOCKHDRSZ);

        block->prev = NULL;
        block->next = set->blocks;
        if (block->next)
            block->next->prev = block;
        set->blocks = block;
    }

    /*
     * OK, do the allocation
     */
    chunk = (AllocChunk) (block->freeptr);

    /* Prepare to initialize the chunk header. */
    VALGRIND_MAKE_MEM_UNDEFINED(chunk, ALLOC_CHUNKHDRSZ);

    block->freeptr += (chunk_size + ALLOC_CHUNKHDRSZ);
    Assert(block->freeptr <= block->endptr);

    chunk->aset = (void *) set;
    chunk->size = chunk_size;
#ifdef MEMORY_CONTEXT_CHECKING
    chunk->requested_size = size;
    /* set mark to catch clobber of "unused" space */
    if (size < chunk->size)
        set_sentinel(AllocChunkGetPointer(chunk), size);
#endif
#ifdef RANDOMIZE_ALLOCATED_MEMORY
    /* fill the allocated space with junk */
    randomize_mem((char *) AllocChunkGetPointer(chunk), size);
#endif

    /* Ensure any padding bytes are marked NOACCESS. */
    VALGRIND_MAKE_MEM_NOACCESS((char *) AllocChunkGetPointer(chunk) + size,
                               chunk_size - size);

    /* Disallow external access to private part of chunk header. */
    VALGRIND_MAKE_MEM_NOACCESS(chunk, ALLOCCHUNK_PRIVATE_LEN);

    return AllocChunkGetPointer(chunk);
}

AllocSetContextCreateInternal()

MemoryContext AllocSetContextCreateInternal	(	MemoryContext	parent,
		const char *	name,
		Size	minContextSize,
		Size	initBlockSize,
		Size	maxBlockSize
	)

Definition at line 378 of file aset.c.

References ALLOC_BLOCKHDRSZ, ALLOC_CHUNK_FRACTION, ALLOC_CHUNK_LIMIT, ALLOC_CHUNKHDRSZ, AllocHugeSizeIsValid, ALLOCSET_DEFAULT_INITSIZE, ALLOCSET_DEFAULT_MINSIZE, ALLOCSET_SEPARATE_THRESHOLD, ALLOCSET_SMALL_INITSIZE, ALLOCSET_SMALL_MINSIZE, AllocSetMethods, AllocBlockData::aset, Assert, AllocBlockData::endptr, ereport, errcode(), errdetail(), errmsg(), ERROR, AllocSetFreeList::first_free, AllocSetContext::freelist, AllocSetContext::freeListIndex, AllocBlockData::freeptr, AllocSetContext::header, AllocSetContext::initBlockSize, malloc, Max, MAXALIGN, AllocSetContext::maxBlockSize, MemoryContextCreate(), MemoryContextStats(), MemSetAligned, name, AllocBlockData::next, MemoryContextData::nextchild, AllocSetFreeList::num_free, offsetof, AllocBlockData::prev, StaticAssertStmt, T_AllocSetContext, TopMemoryContext, and VALGRIND_MAKE_MEM_NOACCESS.

Referenced by GetMemoryChunkContext().

{
    int         freeListIndex;
    Size        firstBlockSize;
    AllocSet    set;
    AllocBlock  block;

    /* Assert we padded AllocChunkData properly */
    StaticAssertStmt(ALLOC_CHUNKHDRSZ == MAXALIGN(ALLOC_CHUNKHDRSZ),
                     "sizeof(AllocChunkData) is not maxaligned");
    StaticAssertStmt(offsetof(AllocChunkData, aset) + sizeof(MemoryContext) ==
                     ALLOC_CHUNKHDRSZ,
                     "padding calculation in AllocChunkData is wrong");

    /*
     * First, validate allocation parameters.  Once these were regular runtime
     * test and elog's, but in practice Asserts seem sufficient because nobody
     * varies their parameters at runtime.  We somewhat arbitrarily enforce a
     * minimum 1K block size.
     */
    Assert(initBlockSize == MAXALIGN(initBlockSize) &&
           initBlockSize >= 1024);
    Assert(maxBlockSize == MAXALIGN(maxBlockSize) &&
           maxBlockSize >= initBlockSize &&
           AllocHugeSizeIsValid(maxBlockSize)); /* must be safe to double */
    Assert(minContextSize == 0 ||
           (minContextSize == MAXALIGN(minContextSize) &&
            minContextSize >= 1024 &&
            minContextSize <= maxBlockSize));

    /*
     * Check whether the parameters match either available freelist.  We do
     * not need to demand a match of maxBlockSize.
     */
    if (minContextSize == ALLOCSET_DEFAULT_MINSIZE &&
        initBlockSize == ALLOCSET_DEFAULT_INITSIZE)
        freeListIndex = 0;
    else if (minContextSize == ALLOCSET_SMALL_MINSIZE &&
             initBlockSize == ALLOCSET_SMALL_INITSIZE)
        freeListIndex = 1;
    else
        freeListIndex = -1;

    /*
     * If a suitable freelist entry exists, just recycle that context.
     */
    if (freeListIndex >= 0)
    {
        AllocSetFreeList *freelist = &context_freelists[freeListIndex];

        if (freelist->first_free != NULL)
        {
            /* Remove entry from freelist */
            set = freelist->first_free;
            freelist->first_free = (AllocSet) set->header.nextchild;
            freelist->num_free--;

            /* Update its maxBlockSize; everything else should be OK */
            set->maxBlockSize = maxBlockSize;

            /* Reinitialize its header, installing correct name and parent */
            MemoryContextCreate((MemoryContext) set,
                                T_AllocSetContext,
                                &AllocSetMethods,
                                parent,
                                name);

            ((MemoryContext) set)->mem_allocated =
                set->keeper->endptr - ((char *) set);

            return (MemoryContext) set;
        }
    }

    /* Determine size of initial block */
    firstBlockSize = MAXALIGN(sizeof(AllocSetContext)) +
        ALLOC_BLOCKHDRSZ + ALLOC_CHUNKHDRSZ;
    if (minContextSize != 0)
        firstBlockSize = Max(firstBlockSize, minContextSize);
    else
        firstBlockSize = Max(firstBlockSize, initBlockSize);

    /*
     * Allocate the initial block.  Unlike other aset.c blocks, it starts with
     * the context header and its block header follows that.
     */
    set = (AllocSet) malloc(firstBlockSize);
    if (set == NULL)
    {
        if (TopMemoryContext)
            MemoryContextStats(TopMemoryContext);
        ereport(ERROR,
                (errcode(ERRCODE_OUT_OF_MEMORY),
                 errmsg("out of memory"),
                 errdetail("Failed while creating memory context \"%s\".",
                           name)));
    }

    /*
     * Avoid writing code that can fail between here and MemoryContextCreate;
     * we'd leak the header/initial block if we ereport in this stretch.
     */

    /* Fill in the initial block's block header */
    block = (AllocBlock) (((char *) set) + MAXALIGN(sizeof(AllocSetContext)));
    block->aset = set;
    block->freeptr = ((char *) block) + ALLOC_BLOCKHDRSZ;
    block->endptr = ((char *) set) + firstBlockSize;
    block->prev = NULL;
    block->next = NULL;

    /* Mark unallocated space NOACCESS; leave the block header alone. */
    VALGRIND_MAKE_MEM_NOACCESS(block->freeptr, block->endptr - block->freeptr);

    /* Remember block as part of block list */
    set->blocks = block;
    /* Mark block as not to be released at reset time */
    set->keeper = block;

    /* Finish filling in aset-specific parts of the context header */
    MemSetAligned(set->freelist, 0, sizeof(set->freelist));

    set->initBlockSize = initBlockSize;
    set->maxBlockSize = maxBlockSize;
    set->nextBlockSize = initBlockSize;
    set->freeListIndex = freeListIndex;

    /*
     * Compute the allocation chunk size limit for this context.  It can't be
     * more than ALLOC_CHUNK_LIMIT because of the fixed number of freelists.
     * If maxBlockSize is small then requests exceeding the maxBlockSize, or
     * even a significant fraction of it, should be treated as large chunks
     * too.  For the typical case of maxBlockSize a power of 2, the chunk size
     * limit will be at most 1/8th maxBlockSize, so that given a stream of
     * requests that are all the maximum chunk size we will waste at most
     * 1/8th of the allocated space.
     *
     * We have to have allocChunkLimit a power of two, because the requested
     * and actually-allocated sizes of any chunk must be on the same side of
     * the limit, else we get confused about whether the chunk is "big".
     *
     * Also, allocChunkLimit must not exceed ALLOCSET_SEPARATE_THRESHOLD.
     */
    StaticAssertStmt(ALLOC_CHUNK_LIMIT == ALLOCSET_SEPARATE_THRESHOLD,
                     "ALLOC_CHUNK_LIMIT != ALLOCSET_SEPARATE_THRESHOLD");

    set->allocChunkLimit = ALLOC_CHUNK_LIMIT;
    while ((Size) (set->allocChunkLimit + ALLOC_CHUNKHDRSZ) >
           (Size) ((maxBlockSize - ALLOC_BLOCKHDRSZ) / ALLOC_CHUNK_FRACTION))
        set->allocChunkLimit >>= 1;

    /* Finally, do the type-independent part of context creation */
    MemoryContextCreate((MemoryContext) set,
                        T_AllocSetContext,
                        &AllocSetMethods,
                        parent,
                        name);

    ((MemoryContext) set)->mem_allocated = firstBlockSize;

    return (MemoryContext) set;
}

AllocSetDelete()

static void AllocSetDelete ( MemoryContext  context )

static

Definition at line 626 of file aset.c.

References AllocSetIsValid, Assert, AssertArg, AllocBlockData::endptr, AllocSetFreeList::first_free, free, AllocSetContext::freelist, AllocBlockData::freeptr, AllocSetContext::header, MemoryContextData::isReset, MAX_FREE_CONTEXTS, MemoryContextData::mem_allocated, MemoryContextResetOnly(), AllocBlockData::next, next, MemoryContextData::nextchild, AllocSetFreeList::num_free, and PG_USED_FOR_ASSERTS_ONLY.

{
    AllocSet    set = (AllocSet) context;
    AllocBlock  block = set->blocks;
    Size        keepersize PG_USED_FOR_ASSERTS_ONLY
    = set->keeper->endptr - ((char *) set);

    AssertArg(AllocSetIsValid(set));

#ifdef MEMORY_CONTEXT_CHECKING
    /* Check for corruption and leaks before freeing */
    AllocSetCheck(context);
#endif

    /*
     * If the context is a candidate for a freelist, put it into that freelist
     * instead of destroying it.
     */
    if (set->freeListIndex >= 0)
    {
        AllocSetFreeList *freelist = &context_freelists[set->freeListIndex];

        /*
         * Reset the context, if it needs it, so that we aren't hanging on to
         * more than the initial malloc chunk.
         */
        if (!context->isReset)
            MemoryContextResetOnly(context);

        /*
         * If the freelist is full, just discard what's already in it.  See
         * comments with context_freelists[].
         */
        if (freelist->num_free >= MAX_FREE_CONTEXTS)
        {
            while (freelist->first_free != NULL)
            {
                AllocSetContext *oldset = freelist->first_free;

                freelist->first_free = (AllocSetContext *) oldset->header.nextchild;
                freelist->num_free--;

                /* All that remains is to free the header/initial block */
                free(oldset);
            }
            Assert(freelist->num_free == 0);
        }

        /* Now add the just-deleted context to the freelist. */
        set->header.nextchild = (MemoryContext) freelist->first_free;
        freelist->first_free = set;
        freelist->num_free++;

        return;
    }

    /* Free all blocks, except the keeper which is part of context header */
    while (block != NULL)
    {
        AllocBlock  next = block->next;

        if (block != set->keeper)
            context->mem_allocated -= block->endptr - ((char *) block);

#ifdef CLOBBER_FREED_MEMORY
        wipe_mem(block, block->freeptr - ((char *) block));
#endif

        if (block != set->keeper)
            free(block);

        block = next;
    }

    Assert(context->mem_allocated == keepersize);

    /* Finally, free the context header, including the keeper block */
    free(set);
}

AllocSetFree()

static void AllocSetFree ( MemoryContext  context, void *  pointer  )

static

Definition at line 992 of file aset.c.

References ALLOC_BLOCKHDRSZ, ALLOC_CHUNKHDRSZ, ALLOCCHUNK_PRIVATE_LEN, AllocPointerGetChunk, AllocSetFreeIndex(), AllocBlockData::aset, AllocChunkData::aset, elog, AllocBlockData::endptr, ERROR, free, AllocBlockData::freeptr, MemoryContextData::mem_allocated, AllocChunkData::size, VALGRIND_MAKE_MEM_DEFINED, and WARNING.

Referenced by AllocSetRealloc().

{
    AllocSet    set = (AllocSet) context;
    AllocChunk  chunk = AllocPointerGetChunk(pointer);

    /* Allow access to private part of chunk header. */
    VALGRIND_MAKE_MEM_DEFINED(chunk, ALLOCCHUNK_PRIVATE_LEN);

#ifdef MEMORY_CONTEXT_CHECKING
    /* Test for someone scribbling on unused space in chunk */
    if (chunk->requested_size < chunk->size)
        if (!sentinel_ok(pointer, chunk->requested_size))
            elog(WARNING, "detected write past chunk end in %s %p",
                 set->header.name, chunk);
#endif

    if (chunk->size > set->allocChunkLimit)
    {
        /*
         * Big chunks are certain to have been allocated as single-chunk
         * blocks.  Just unlink that block and return it to malloc().
         */
        AllocBlock  block = (AllocBlock) (((char *) chunk) - ALLOC_BLOCKHDRSZ);

        /*
         * Try to verify that we have a sane block pointer: it should
         * reference the correct aset, and freeptr and endptr should point
         * just past the chunk.
         */
        if (block->aset != set ||
            block->freeptr != block->endptr ||
            block->freeptr != ((char *) block) +
            (chunk->size + ALLOC_BLOCKHDRSZ + ALLOC_CHUNKHDRSZ))
            elog(ERROR, "could not find block containing chunk %p", chunk);

        /* OK, remove block from aset's list and free it */
        if (block->prev)
            block->prev->next = block->next;
        else
            set->blocks = block->next;
        if (block->next)
            block->next->prev = block->prev;

        context->mem_allocated -= block->endptr - ((char *) block);

#ifdef CLOBBER_FREED_MEMORY
        wipe_mem(block, block->freeptr - ((char *) block));
#endif
        free(block);
    }
    else
    {
        /* Normal case, put the chunk into appropriate freelist */
        int         fidx = AllocSetFreeIndex(chunk->size);

        chunk->aset = (void *) set->freelist[fidx];

#ifdef CLOBBER_FREED_MEMORY
        wipe_mem(pointer, chunk->size);
#endif

#ifdef MEMORY_CONTEXT_CHECKING
        /* Reset requested_size to 0 in chunks that are on freelist */
        chunk->requested_size = 0;
#endif
        set->freelist[fidx] = chunk;
    }
}

AllocSetFreeIndex()

static int AllocSetFreeIndex ( Size  size )

inlinestatic

Definition at line 308 of file aset.c.

References ALLOC_CHUNK_LIMIT, ALLOC_MINBITS, ALLOCSET_NUM_FREELISTS, Assert, idx(), pg_leftmost_one_pos, and StaticAssertStmt.

Referenced by AllocSetAlloc(), and AllocSetFree().

{
    int         idx;

    if (size > (1 << ALLOC_MINBITS))
    {
        /*----------
         * At this point we must compute ceil(log2(size >> ALLOC_MINBITS)).
         * This is the same as
         *      pg_leftmost_one_pos32((size - 1) >> ALLOC_MINBITS) + 1
         * or equivalently
         *      pg_leftmost_one_pos32(size - 1) - ALLOC_MINBITS + 1
         *
         * However, rather than just calling that function, we duplicate the
         * logic here, allowing an additional optimization.  It's reasonable
         * to assume that ALLOC_CHUNK_LIMIT fits in 16 bits, so we can unroll
         * the byte-at-a-time loop in pg_leftmost_one_pos32 and just handle
         * the last two bytes.
         *
         * Yes, this function is enough of a hot-spot to make it worth this
         * much trouble.
         *----------
         */
#ifdef HAVE__BUILTIN_CLZ
        idx = 31 - __builtin_clz((uint32) size - 1) - ALLOC_MINBITS + 1;
#else
        uint32      t,
                    tsize;

        /* Statically assert that we only have a 16-bit input value. */
        StaticAssertStmt(ALLOC_CHUNK_LIMIT < (1 << 16),
                         "ALLOC_CHUNK_LIMIT must be less than 64kB");

        tsize = size - 1;
        t = tsize >> 8;
        idx = t ? pg_leftmost_one_pos[t] + 8 : pg_leftmost_one_pos[tsize];
        idx -= ALLOC_MINBITS - 1;
#endif

        Assert(idx < ALLOCSET_NUM_FREELISTS);
    }
    else
        idx = 0;

    return idx;
}

AllocSetGetChunkSpace()

static Size AllocSetGetChunkSpace ( MemoryContext  context, void *  pointer  )

static

Definition at line 1303 of file aset.c.

References ALLOC_CHUNKHDRSZ, ALLOCCHUNK_PRIVATE_LEN, AllocPointerGetChunk, AllocChunkData::size, VALGRIND_MAKE_MEM_DEFINED, and VALGRIND_MAKE_MEM_NOACCESS.

{
    AllocChunk  chunk = AllocPointerGetChunk(pointer);
    Size        result;

    VALGRIND_MAKE_MEM_DEFINED(chunk, ALLOCCHUNK_PRIVATE_LEN);
    result = chunk->size + ALLOC_CHUNKHDRSZ;
    VALGRIND_MAKE_MEM_NOACCESS(chunk, ALLOCCHUNK_PRIVATE_LEN);
    return result;
}

AllocSetIsEmpty()

static bool AllocSetIsEmpty ( MemoryContext  context )

static

Definition at line 1319 of file aset.c.

References MemoryContextData::isReset.

{
    /*
     * For now, we say "empty" only if the context is new or just reset. We
     * could examine the freelists to determine if all space has been freed,
     * but it's not really worth the trouble for present uses of this
     * functionality.
     */
    if (context->isReset)
        return true;
    return false;
}

AllocSetRealloc()

static void * AllocSetRealloc ( MemoryContext  context, void *  pointer, Size  size  )

static

Definition at line 1074 of file aset.c.

References ALLOC_BLOCKHDRSZ, ALLOC_CHUNKHDRSZ, ALLOCCHUNK_PRIVATE_LEN, AllocChunkGetPointer, AllocPointerGetChunk, AllocSetAlloc(), AllocSetFree(), AllocBlockData::aset, elog, AllocBlockData::endptr, ERROR, AllocBlockData::freeptr, Max, MAXALIGN, MemoryContextData::mem_allocated, realloc, AllocChunkData::size, VALGRIND_MAKE_MEM_DEFINED, VALGRIND_MAKE_MEM_NOACCESS, VALGRIND_MAKE_MEM_UNDEFINED, and WARNING.

{
    AllocSet    set = (AllocSet) context;
    AllocChunk  chunk = AllocPointerGetChunk(pointer);
    Size        oldsize;

    /* Allow access to private part of chunk header. */
    VALGRIND_MAKE_MEM_DEFINED(chunk, ALLOCCHUNK_PRIVATE_LEN);

    oldsize = chunk->size;

#ifdef MEMORY_CONTEXT_CHECKING
    /* Test for someone scribbling on unused space in chunk */
    if (chunk->requested_size < oldsize)
        if (!sentinel_ok(pointer, chunk->requested_size))
            elog(WARNING, "detected write past chunk end in %s %p",
                 set->header.name, chunk);
#endif

    if (oldsize > set->allocChunkLimit)
    {
        /*
         * The chunk must have been allocated as a single-chunk block.  Use
         * realloc() to make the containing block bigger, or smaller, with
         * minimum space wastage.
         */
        AllocBlock  block = (AllocBlock) (((char *) chunk) - ALLOC_BLOCKHDRSZ);
        Size        chksize;
        Size        blksize;
        Size        oldblksize;

        /*
         * Try to verify that we have a sane block pointer: it should
         * reference the correct aset, and freeptr and endptr should point
         * just past the chunk.
         */
        if (block->aset != set ||
            block->freeptr != block->endptr ||
            block->freeptr != ((char *) block) +
            (oldsize + ALLOC_BLOCKHDRSZ + ALLOC_CHUNKHDRSZ))
            elog(ERROR, "could not find block containing chunk %p", chunk);

        /*
         * Even if the new request is less than set->allocChunkLimit, we stick
         * with the single-chunk block approach.  Therefore we need
         * chunk->size to be bigger than set->allocChunkLimit, so we don't get
         * confused about the chunk's status in future calls.
         */
        chksize = Max(size, set->allocChunkLimit + 1);
        chksize = MAXALIGN(chksize);

        /* Do the realloc */
        blksize = chksize + ALLOC_BLOCKHDRSZ + ALLOC_CHUNKHDRSZ;
        oldblksize = block->endptr - ((char *) block);

        block = (AllocBlock) realloc(block, blksize);
        if (block == NULL)
        {
            /* Disallow external access to private part of chunk header. */
            VALGRIND_MAKE_MEM_NOACCESS(chunk, ALLOCCHUNK_PRIVATE_LEN);
            return NULL;
        }

        /* updated separately, not to underflow when (oldblksize > blksize) */
        context->mem_allocated -= oldblksize;
        context->mem_allocated += blksize;

        block->freeptr = block->endptr = ((char *) block) + blksize;

        /* Update pointers since block has likely been moved */
        chunk = (AllocChunk) (((char *) block) + ALLOC_BLOCKHDRSZ);
        pointer = AllocChunkGetPointer(chunk);
        if (block->prev)
            block->prev->next = block;
        else
            set->blocks = block;
        if (block->next)
            block->next->prev = block;
        chunk->size = chksize;

#ifdef MEMORY_CONTEXT_CHECKING
#ifdef RANDOMIZE_ALLOCATED_MEMORY
        /* We can only fill the extra space if we know the prior request */
        if (size > chunk->requested_size)
            randomize_mem((char *) pointer + chunk->requested_size,
                          size - chunk->requested_size);
#endif

        /*
         * realloc() (or randomize_mem()) will have left any newly-allocated
         * part UNDEFINED, but we may need to adjust trailing bytes from the
         * old allocation.
         */
#ifdef USE_VALGRIND
        if (oldsize > chunk->requested_size)
            VALGRIND_MAKE_MEM_UNDEFINED((char *) pointer + chunk->requested_size,
                                        oldsize - chunk->requested_size);
#endif

        chunk->requested_size = size;

        /* set mark to catch clobber of "unused" space */
        if (size < chunk->size)
            set_sentinel(pointer, size);
#else                           /* !MEMORY_CONTEXT_CHECKING */

        /*
         * We don't know how much of the old chunk size was the actual
         * allocation; it could have been as small as one byte.  We have to be
         * conservative and just mark the entire old portion DEFINED.
         */
        VALGRIND_MAKE_MEM_DEFINED(pointer, oldsize);
#endif

        /* Ensure any padding bytes are marked NOACCESS. */
        VALGRIND_MAKE_MEM_NOACCESS((char *) pointer + size, chksize - size);

        /* Disallow external access to private part of chunk header. */
        VALGRIND_MAKE_MEM_NOACCESS(chunk, ALLOCCHUNK_PRIVATE_LEN);

        return pointer;
    }

    /*
     * Chunk sizes are aligned to power of 2 in AllocSetAlloc().  Maybe the
     * allocated area already is >= the new size.  (In particular, we will
     * fall out here if the requested size is a decrease.)
     */
    else if (oldsize >= size)
    {
#ifdef MEMORY_CONTEXT_CHECKING
        Size        oldrequest = chunk->requested_size;

#ifdef RANDOMIZE_ALLOCATED_MEMORY
        /* We can only fill the extra space if we know the prior request */
        if (size > oldrequest)
            randomize_mem((char *) pointer + oldrequest,
                          size - oldrequest);
#endif

        chunk->requested_size = size;

        /*
         * If this is an increase, mark any newly-available part UNDEFINED.
         * Otherwise, mark the obsolete part NOACCESS.
         */
        if (size > oldrequest)
            VALGRIND_MAKE_MEM_UNDEFINED((char *) pointer + oldrequest,
                                        size - oldrequest);
        else
            VALGRIND_MAKE_MEM_NOACCESS((char *) pointer + size,
                                       oldsize - size);

        /* set mark to catch clobber of "unused" space */
        if (size < oldsize)
            set_sentinel(pointer, size);
#else                           /* !MEMORY_CONTEXT_CHECKING */

        /*
         * We don't have the information to determine whether we're growing
         * the old request or shrinking it, so we conservatively mark the
         * entire new allocation DEFINED.
         */
        VALGRIND_MAKE_MEM_NOACCESS(pointer, oldsize);
        VALGRIND_MAKE_MEM_DEFINED(pointer, size);
#endif

        /* Disallow external access to private part of chunk header. */
        VALGRIND_MAKE_MEM_NOACCESS(chunk, ALLOCCHUNK_PRIVATE_LEN);

        return pointer;
    }
    else
    {
        /*
         * Enlarge-a-small-chunk case.  We just do this by brute force, ie,
         * allocate a new chunk and copy the data.  Since we know the existing
         * data isn't huge, this won't involve any great memcpy expense, so
         * it's not worth being smarter.  (At one time we tried to avoid
         * memcpy when it was possible to enlarge the chunk in-place, but that
         * turns out to misbehave unpleasantly for repeated cycles of
         * palloc/repalloc/pfree: the eventually freed chunks go into the
         * wrong freelist for the next initial palloc request, and so we leak
         * memory indefinitely.  See pgsql-hackers archives for 2007-08-11.)
         */
        AllocPointer newPointer;

        /* allocate new chunk */
        newPointer = AllocSetAlloc((MemoryContext) set, size);

        /* leave immediately if request was not completed */
        if (newPointer == NULL)
        {
            /* Disallow external access to private part of chunk header. */
            VALGRIND_MAKE_MEM_NOACCESS(chunk, ALLOCCHUNK_PRIVATE_LEN);
            return NULL;
        }

        /*
         * AllocSetAlloc() may have returned a region that is still NOACCESS.
         * Change it to UNDEFINED for the moment; memcpy() will then transfer
         * definedness from the old allocation to the new.  If we know the old
         * allocation, copy just that much.  Otherwise, make the entire old
         * chunk defined to avoid errors as we copy the currently-NOACCESS
         * trailing bytes.
         */
        VALGRIND_MAKE_MEM_UNDEFINED(newPointer, size);
#ifdef MEMORY_CONTEXT_CHECKING
        oldsize = chunk->requested_size;
#else
        VALGRIND_MAKE_MEM_DEFINED(pointer, oldsize);
#endif

        /* transfer existing data (certain to fit) */
        memcpy(newPointer, pointer, oldsize);

        /* free old chunk */
        AllocSetFree((MemoryContext) set, pointer);

        return newPointer;
    }
}

AllocSetReset()

static void AllocSetReset ( MemoryContext  context )

static

Definition at line 558 of file aset.c.

References ALLOC_BLOCKHDRSZ, AllocSetIsValid, Assert, AssertArg, AllocBlockData::endptr, free, AllocBlockData::freeptr, MemoryContextData::mem_allocated, MemSetAligned, AllocBlockData::next, next, PG_USED_FOR_ASSERTS_ONLY, AllocBlockData::prev, and VALGRIND_MAKE_MEM_NOACCESS.

{
    AllocSet    set = (AllocSet) context;
    AllocBlock  block;
    Size        keepersize PG_USED_FOR_ASSERTS_ONLY
    = set->keeper->endptr - ((char *) set);

    AssertArg(AllocSetIsValid(set));

#ifdef MEMORY_CONTEXT_CHECKING
    /* Check for corruption and leaks before freeing */
    AllocSetCheck(context);
#endif

    /* Clear chunk freelists */
    MemSetAligned(set->freelist, 0, sizeof(set->freelist));

    block = set->blocks;

    /* New blocks list will be just the keeper block */
    set->blocks = set->keeper;

    while (block != NULL)
    {
        AllocBlock  next = block->next;

        if (block == set->keeper)
        {
            /* Reset the block, but don't return it to malloc */
            char       *datastart = ((char *) block) + ALLOC_BLOCKHDRSZ;

#ifdef CLOBBER_FREED_MEMORY
            wipe_mem(datastart, block->freeptr - datastart);
#else
            /* wipe_mem() would have done this */
            VALGRIND_MAKE_MEM_NOACCESS(datastart, block->freeptr - datastart);
#endif
            block->freeptr = datastart;
            block->prev = NULL;
            block->next = NULL;
        }
        else
        {
            /* Normal case, release the block */
            context->mem_allocated -= block->endptr - ((char *) block);

#ifdef CLOBBER_FREED_MEMORY
            wipe_mem(block, block->freeptr - ((char *) block));
#endif
            free(block);
        }
        block = next;
    }

    Assert(context->mem_allocated == keepersize);

    /* Reset block size allocation sequence, too */
    set->nextBlockSize = set->initBlockSize;
}

AllocSetStats()

static void AllocSetStats ( MemoryContext  context, MemoryStatsPrintFunc  printfunc, void *  passthru, MemoryContextCounters *  totals  )

static

Definition at line 1341 of file aset.c.

References ALLOC_BLOCKHDRSZ, ALLOC_CHUNKHDRSZ, ALLOC_MINBITS, ALLOCCHUNK_PRIVATE_LEN, ALLOCSET_NUM_FREELISTS, AllocBlockData::aset, AllocChunkData::aset, Assert, elog, AllocBlockData::endptr, MemoryContextCounters::freechunks, AllocBlockData::freeptr, MemoryContextCounters::freespace, MAXALIGN, MemoryContextData::mem_allocated, name, MemoryContextCounters::nblocks, AllocBlockData::next, AllocBlockData::prev, AllocChunkData::size, snprintf, MemoryContextCounters::totalspace, VALGRIND_MAKE_MEM_DEFINED, VALGRIND_MAKE_MEM_NOACCESS, and WARNING.

{
    AllocSet    set = (AllocSet) context;
    Size        nblocks = 0;
    Size        freechunks = 0;
    Size        totalspace;
    Size        freespace = 0;
    AllocBlock  block;
    int         fidx;

    /* Include context header in totalspace */
    totalspace = MAXALIGN(sizeof(AllocSetContext));

    for (block = set->blocks; block != NULL; block = block->next)
    {
        nblocks++;
        totalspace += block->endptr - ((char *) block);
        freespace += block->endptr - block->freeptr;
    }
    for (fidx = 0; fidx < ALLOCSET_NUM_FREELISTS; fidx++)
    {
        AllocChunk  chunk;

        for (chunk = set->freelist[fidx]; chunk != NULL;
             chunk = (AllocChunk) chunk->aset)
        {
            freechunks++;
            freespace += chunk->size + ALLOC_CHUNKHDRSZ;
        }
    }

    if (printfunc)
    {
        char        stats_string[200];

        snprintf(stats_string, sizeof(stats_string),
                 "%zu total in %zd blocks; %zu free (%zd chunks); %zu used",
                 totalspace, nblocks, freespace, freechunks,
                 totalspace - freespace);
        printfunc(context, passthru, stats_string);
    }

    if (totals)
    {
        totals->nblocks += nblocks;
        totals->freechunks += freechunks;
        totals->totalspace += totalspace;
        totals->freespace += freespace;
    }
}

Variable Documentation

AllocSetMethods

const MemoryContextMethods AllocSetMethods

static

Initial value:

= {
    AllocSetAlloc,
    AllocSetFree,
    AllocSetRealloc,
    AllocSetReset,
    AllocSetDelete,
    AllocSetGetChunkSpace,
    AllocSetIsEmpty,
    AllocSetStats



}

Definition at line 284 of file aset.c.

Referenced by AllocSetContextCreateInternal().

context_freelists

AllocSetFreeList context_freelists[2]

static

Initial value:

=
{
    {
        0, NULL
    },
    {
        0, NULL
    }
}

Definition at line 253 of file aset.c.