slab.c File Reference

#include "postgres.h"
#include "lib/ilist.h"
#include "utils/memdebug.h"
#include "utils/memutils.h"
#include "utils/memutils_memorychunk.h"
#include "utils/memutils_internal.h"

Include dependency graph for slab.c:

Go to the source code of this file.

Data Structures
struct	SlabContext
struct	SlabBlock

Macros
#define	Slab_BLOCKHDRSZ   MAXALIGN(sizeof(SlabBlock))
#define	Slab_CONTEXT_HDRSZ(chunksPerBlock)   sizeof(SlabContext)
#define	SLAB_BLOCKLIST_COUNT   3
#define	SLAB_MAXIMUM_EMPTY_BLOCKS   10
#define	Slab_CHUNKHDRSZ   sizeof(MemoryChunk)
#define	SlabChunkGetPointer(chk)    ((void *) (((char *) (chk)) + sizeof(MemoryChunk)))
#define	SlabBlockGetChunk(slab, block, n)
#define	SlabIsValid(set)   (PointerIsValid(set) && IsA(set, SlabContext))
#define	SlabBlockIsValid(block)    (PointerIsValid(block) && SlabIsValid((block)->slab))

Typedefs
typedef struct SlabContext	SlabContext
typedef struct SlabBlock	SlabBlock

Functions
static int32	SlabBlocklistIndex (SlabContext *slab, int nfree)
static int32	SlabFindNextBlockListIndex (SlabContext *slab)
static MemoryChunk *	SlabGetNextFreeChunk (SlabContext *slab, SlabBlock *block)
MemoryContext	SlabContextCreate (MemoryContext parent, const char *name, Size blockSize, Size chunkSize)
void	SlabReset (MemoryContext context)
void	SlabDelete (MemoryContext context)
void *	SlabAlloc (MemoryContext context, Size size)
void	SlabFree (void *pointer)
void *	SlabRealloc (void *pointer, Size size)
MemoryContext	SlabGetChunkContext (void *pointer)
Size	SlabGetChunkSpace (void *pointer)
bool	SlabIsEmpty (MemoryContext context)
void	SlabStats (MemoryContext context, MemoryStatsPrintFunc printfunc, void *passthru, MemoryContextCounters *totals, bool print_to_stderr)

Macro Definition Documentation

Slab_BLOCKHDRSZ

#define Slab_BLOCKHDRSZ   MAXALIGN(sizeof(SlabBlock))

Definition at line 77 of file slab.c.

SLAB_BLOCKLIST_COUNT

#define SLAB_BLOCKLIST_COUNT   3

Definition at line 95 of file slab.c.

Slab_CHUNKHDRSZ

#define Slab_CHUNKHDRSZ   sizeof(MemoryChunk)

Definition at line 157 of file slab.c.

Slab_CONTEXT_HDRSZ

#define Slab_CONTEXT_HDRSZ

(

chunksPerBlock

)

sizeof(SlabContext)

Definition at line 88 of file slab.c.

SLAB_MAXIMUM_EMPTY_BLOCKS

#define SLAB_MAXIMUM_EMPTY_BLOCKS   10

Definition at line 98 of file slab.c.

SlabBlockGetChunk

#define SlabBlockGetChunk	(		slab,
			block,
			n
	)

Value:

    ((MemoryChunk *) ((char *) (block) + Slab_BLOCKHDRSZ    \
                    + ((n) * (slab)->fullChunkSize)))

Definition at line 165 of file slab.c.

SlabBlockIsValid

#define SlabBlockIsValid

(

block

)

(PointerIsValid(block) && SlabIsValid((block)->slab))

Definition at line 202 of file slab.c.

SlabChunkGetPointer

#define SlabChunkGetPointer

(

chk

)

((void *) (((char *) (chk)) + sizeof(MemoryChunk)))

Definition at line 158 of file slab.c.

SlabIsValid

#define SlabIsValid

(

set

)

(PointerIsValid(set) && IsA(set, SlabContext))

Definition at line 196 of file slab.c.

Typedef Documentation

SlabBlock

typedef struct SlabBlock SlabBlock

SlabContext

typedef struct SlabContext SlabContext

Function Documentation

SlabAlloc()

void* SlabAlloc	(	MemoryContext	context,
		Size	size
	)

Definition at line 499 of file slab.c.

{
    SlabContext *slab = (SlabContext *) context;
    SlabBlock  *block;
    MemoryChunk *chunk;
 
    Assert(SlabIsValid(slab));
 
    /* sanity check that this is pointing to a valid blocklist */
    Assert(slab->curBlocklistIndex >= 0);
    Assert(slab->curBlocklistIndex <= SlabBlocklistIndex(slab, slab->chunksPerBlock));
 
    /* make sure we only allow correct request size */
    if (unlikely(size != slab->chunkSize))
        elog(ERROR, "unexpected alloc chunk size %zu (expected %u)",
             size, slab->chunkSize);
 
    /*
     * Handle the case when there are no partially filled blocks available.
     * SlabFree() will have updated the curBlocklistIndex setting it to zero
     * to indicate that it has freed the final block.  Also later in
     * SlabAlloc() we will set the curBlocklistIndex to zero if we end up
     * filling the final block.
     */
    if (unlikely(slab->curBlocklistIndex == 0))
    {
        dlist_head *blocklist;
        int         blocklist_idx;
 
        /* to save allocating a new one, first check the empty blocks list */
        if (dclist_count(&slab->emptyblocks) > 0)
        {
            dlist_node *node = dclist_pop_head_node(&slab->emptyblocks);
 
            block = dlist_container(SlabBlock, node, node);
 
            /*
             * SlabFree() should have left this block in a valid state with
             * all chunks free.  Ensure that's the case.
             */
            Assert(block->nfree == slab->chunksPerBlock);
 
            /* fetch the next chunk from this block */
            chunk = SlabGetNextFreeChunk(slab, block);
        }
        else
        {
            block = (SlabBlock *) malloc(slab->blockSize);
 
            if (unlikely(block == NULL))
                return NULL;
 
            block->slab = slab;
            context->mem_allocated += slab->blockSize;
 
            /* use the first chunk in the new block */
            chunk = SlabBlockGetChunk(slab, block, 0);
 
            block->nfree = slab->chunksPerBlock - 1;
            block->unused = SlabBlockGetChunk(slab, block, 1);
            block->freehead = NULL;
            block->nunused = slab->chunksPerBlock - 1;
        }
 
        /* find the blocklist element for storing blocks with 1 used chunk */
        blocklist_idx = SlabBlocklistIndex(slab, block->nfree);
        blocklist = &slab->blocklist[blocklist_idx];
 
        /* this better be empty.  We just added a block thinking it was */
        Assert(dlist_is_empty(blocklist));
 
        dlist_push_head(blocklist, &block->node);
 
        slab->curBlocklistIndex = blocklist_idx;
    }
    else
    {
        dlist_head *blocklist = &slab->blocklist[slab->curBlocklistIndex];
        int         new_blocklist_idx;
 
        Assert(!dlist_is_empty(blocklist));
 
        /* grab the block from the blocklist */
        block = dlist_head_element(SlabBlock, node, blocklist);
 
        /* make sure we actually got a valid block, with matching nfree */
        Assert(block != NULL);
        Assert(slab->curBlocklistIndex == SlabBlocklistIndex(slab, block->nfree));
        Assert(block->nfree > 0);
 
        /* fetch the next chunk from this block */
        chunk = SlabGetNextFreeChunk(slab, block);
 
        /* get the new blocklist index based on the new free chunk count */
        new_blocklist_idx = SlabBlocklistIndex(slab, block->nfree);
 
        /*
         * Handle the case where the blocklist index changes.  This also deals
         * with blocks becoming full as only full blocks go at index 0.
         */
        if (unlikely(slab->curBlocklistIndex != new_blocklist_idx))
        {
            dlist_delete_from(blocklist, &block->node);
            dlist_push_head(&slab->blocklist[new_blocklist_idx], &block->node);
 
            if (dlist_is_empty(blocklist))
                slab->curBlocklistIndex = SlabFindNextBlockListIndex(slab);
        }
    }
 
    /*
     * Check that the chunk pointer is actually somewhere on the block and is
     * aligned as expected.
     */
    Assert(chunk >= SlabBlockGetChunk(slab, block, 0));
    Assert(chunk <= SlabBlockGetChunk(slab, block, slab->chunksPerBlock - 1));
    Assert(SlabChunkMod(slab, block, chunk) == 0);
 
    /* Prepare to initialize the chunk header. */
    VALGRIND_MAKE_MEM_UNDEFINED(chunk, Slab_CHUNKHDRSZ);
 
    MemoryChunkSetHdrMask(chunk, block, MAXALIGN(slab->chunkSize),
                          MCTX_SLAB_ID);
#ifdef MEMORY_CONTEXT_CHECKING
    /* slab mark to catch clobber of "unused" space */
    Assert(slab->chunkSize < (slab->fullChunkSize - Slab_CHUNKHDRSZ));
    set_sentinel(MemoryChunkGetPointer(chunk), size);
    VALGRIND_MAKE_MEM_NOACCESS(((char *) chunk) +
                               Slab_CHUNKHDRSZ + slab->chunkSize,
                               slab->fullChunkSize -
                               (slab->chunkSize + Slab_CHUNKHDRSZ));
#endif
 
#ifdef RANDOMIZE_ALLOCATED_MEMORY
    /* fill the allocated space with junk */
    randomize_mem((char *) MemoryChunkGetPointer(chunk), size);
#endif
 
    /* Disallow access to the chunk header. */
    VALGRIND_MAKE_MEM_NOACCESS(chunk, Slab_CHUNKHDRSZ);
 
    return MemoryChunkGetPointer(chunk);
}

References Assert(), SlabContext::blocklist, SlabContext::blockSize, SlabContext::chunkSize, SlabContext::chunksPerBlock, SlabContext::curBlocklistIndex, dclist_count(), dclist_pop_head_node(), dlist_container, dlist_delete_from(), dlist_head_element, dlist_is_empty(), dlist_push_head(), elog(), SlabContext::emptyblocks, ERROR, SlabBlock::freehead, SlabContext::fullChunkSize, malloc, MAXALIGN, MCTX_SLAB_ID, MemoryContextData::mem_allocated, MemoryChunkGetPointer, MemoryChunkSetHdrMask(), SlabBlock::nfree, SlabBlock::node, SlabBlock::nunused, SlabBlock::slab, Slab_CHUNKHDRSZ, SlabBlockGetChunk, SlabBlocklistIndex(), SlabFindNextBlockListIndex(), SlabGetNextFreeChunk(), SlabIsValid, unlikely, SlabBlock::unused, VALGRIND_MAKE_MEM_NOACCESS, and VALGRIND_MAKE_MEM_UNDEFINED.

SlabBlocklistIndex()

static int32 SlabBlocklistIndex ( SlabContext *  slab, int  nfree  )

inlinestatic

Definition at line 211 of file slab.c.

{
    int32       index;
    int32       blocklist_shift = slab->blocklist_shift;
 
    Assert(nfree >= 0 && nfree <= slab->chunksPerBlock);
 
    /*
     * Determine the blocklist index based on the number of free chunks.  We
     * must ensure that 0 free chunks is dedicated to index 0.  Everything
     * else must be >= 1 and < SLAB_BLOCKLIST_COUNT.
     *
     * To make this as efficient as possible, we exploit some two's complement
     * arithmetic where we reverse the sign before bit shifting.  This results
     * in an nfree of 0 using index 0 and anything non-zero staying non-zero.
     * This is exploiting 0 and -0 being the same in two's complement.  When
     * we're done, we just need to flip the sign back over again for a
     * positive index.
     */
    index = -((-nfree) >> blocklist_shift);
 
    if (nfree == 0)
        Assert(index == 0);
    else
        Assert(index >= 1 && index < SLAB_BLOCKLIST_COUNT);
 
    return index;
}

References Assert(), SlabContext::blocklist_shift, and SLAB_BLOCKLIST_COUNT.

Referenced by SlabAlloc(), and SlabFree().

SlabContextCreate()

MemoryContext SlabContextCreate	(	MemoryContext	parent,
		const char *	name,
		Size	blockSize,
		Size	chunkSize
	)

Definition at line 322 of file slab.c.

{
    int         chunksPerBlock;
    Size        fullChunkSize;
    SlabContext *slab;
    int         i;
 
    /* ensure MemoryChunk's size is properly maxaligned */
    StaticAssertDecl(Slab_CHUNKHDRSZ == MAXALIGN(Slab_CHUNKHDRSZ),
                     "sizeof(MemoryChunk) is not maxaligned");
    Assert(blockSize <= MEMORYCHUNK_MAX_BLOCKOFFSET);
 
    /*
     * Ensure there's enough space to store the pointer to the next free chunk
     * in the memory of the (otherwise) unused allocation.
     */
    if (chunkSize < sizeof(MemoryChunk *))
        chunkSize = sizeof(MemoryChunk *);
 
    /* length of the maxaligned chunk including the chunk header  */
#ifdef MEMORY_CONTEXT_CHECKING
    /* ensure there's always space for the sentinel byte */
    fullChunkSize = Slab_CHUNKHDRSZ + MAXALIGN(chunkSize + 1);
#else
    fullChunkSize = Slab_CHUNKHDRSZ + MAXALIGN(chunkSize);
#endif
 
    Assert(fullChunkSize <= MEMORYCHUNK_MAX_VALUE);
 
    /* compute the number of chunks that will fit on each block */
    chunksPerBlock = (blockSize - Slab_BLOCKHDRSZ) / fullChunkSize;
 
    /* Make sure the block can store at least one chunk. */
    if (chunksPerBlock == 0)
        elog(ERROR, "block size %zu for slab is too small for %zu-byte chunks",
             blockSize, chunkSize);
 
 
 
    slab = (SlabContext *) malloc(Slab_CONTEXT_HDRSZ(chunksPerBlock));
    if (slab == NULL)
    {
        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 if we ereport in this stretch.
     */
 
    /* Fill in SlabContext-specific header fields */
    slab->chunkSize = (uint32) chunkSize;
    slab->fullChunkSize = (uint32) fullChunkSize;
    slab->blockSize = (uint32) blockSize;
    slab->chunksPerBlock = chunksPerBlock;
    slab->curBlocklistIndex = 0;
 
    /*
     * Compute a shift that guarantees that shifting chunksPerBlock with it is
     * < SLAB_BLOCKLIST_COUNT - 1.  The reason that we subtract 1 from
     * SLAB_BLOCKLIST_COUNT in this calculation is that we reserve the 0th
     * blocklist element for blocks which have no free chunks.
     *
     * We calculate the number of bits to shift by rather than a divisor to
     * divide by as performing division each time we need to find the
     * blocklist index would be much slower.
     */
    slab->blocklist_shift = 0;
    while ((slab->chunksPerBlock >> slab->blocklist_shift) >= (SLAB_BLOCKLIST_COUNT - 1))
        slab->blocklist_shift++;
 
    /* initialize the list to store empty blocks to be reused */
    dclist_init(&slab->emptyblocks);
 
    /* initialize each blocklist slot */
    for (i = 0; i < SLAB_BLOCKLIST_COUNT; i++)
        dlist_init(&slab->blocklist[i]);
 
#ifdef MEMORY_CONTEXT_CHECKING
    /* set the isChunkFree pointer right after the end of the context */
    slab->isChunkFree = (bool *) ((char *) slab + sizeof(SlabContext));
#endif
 
    /* Finally, do the type-independent part of context creation */
    MemoryContextCreate((MemoryContext) slab,
                        T_SlabContext,
                        MCTX_SLAB_ID,
                        parent,
                        name);
 
    return (MemoryContext) slab;
}

References Assert(), SlabContext::blocklist, SlabContext::blocklist_shift, SlabContext::blockSize, SlabContext::chunkSize, SlabContext::chunksPerBlock, SlabContext::curBlocklistIndex, dclist_init(), dlist_init(), elog(), SlabContext::emptyblocks, ereport, errcode(), errdetail(), errmsg(), ERROR, SlabContext::fullChunkSize, i, malloc, MAXALIGN, MCTX_SLAB_ID, MEMORYCHUNK_MAX_BLOCKOFFSET, MEMORYCHUNK_MAX_VALUE, MemoryContextCreate(), MemoryContextStats(), name, Slab_BLOCKHDRSZ, SLAB_BLOCKLIST_COUNT, Slab_CHUNKHDRSZ, Slab_CONTEXT_HDRSZ, StaticAssertDecl, and TopMemoryContext.

Referenced by ReorderBufferAllocate().

SlabDelete()

void SlabDelete

(

MemoryContext

context

)

Definition at line 485 of file slab.c.

{
    /* Reset to release all the SlabBlocks */
    SlabReset(context);
    /* And free the context header */
    free(context);
}

References free, and SlabReset().

SlabFindNextBlockListIndex()

static int32 SlabFindNextBlockListIndex ( SlabContext *  slab )

static

Definition at line 251 of file slab.c.

{
    /* start at 1 as blocklist[0] is for full blocks. */
    for (int i = 1; i < SLAB_BLOCKLIST_COUNT; i++)
    {
        /* return the first found non-empty index */
        if (!dlist_is_empty(&slab->blocklist[i]))
            return i;
    }
 
    /* no blocks with free space */
    return 0;
}

References SlabContext::blocklist, dlist_is_empty(), i, and SLAB_BLOCKLIST_COUNT.

Referenced by SlabAlloc(), and SlabFree().

SlabFree()

void SlabFree

(

void *

pointer

)

Definition at line 648 of file slab.c.

{
    MemoryChunk *chunk = PointerGetMemoryChunk(pointer);
    SlabBlock  *block;
    SlabContext *slab;
    int         curBlocklistIdx;
    int         newBlocklistIdx;
 
    /* Allow access to the chunk header. */
    VALGRIND_MAKE_MEM_DEFINED(chunk, Slab_CHUNKHDRSZ);
 
    block = MemoryChunkGetBlock(chunk);
 
    /*
     * For speed reasons we just Assert that the referenced block is good.
     * Future field experience may show that this Assert had better become a
     * regular runtime test-and-elog check.
     */
    Assert(SlabBlockIsValid(block));
    slab = block->slab;
 
#ifdef MEMORY_CONTEXT_CHECKING
    /* Test for someone scribbling on unused space in chunk */
    Assert(slab->chunkSize < (slab->fullChunkSize - Slab_CHUNKHDRSZ));
    if (!sentinel_ok(pointer, slab->chunkSize))
        elog(WARNING, "detected write past chunk end in %s %p",
             slab->header.name, chunk);
#endif
 
    /* push this chunk onto the head of the block's free list */
    *(MemoryChunk **) pointer = block->freehead;
    block->freehead = chunk;
 
    block->nfree++;
 
    Assert(block->nfree > 0);
    Assert(block->nfree <= slab->chunksPerBlock);
 
#ifdef CLOBBER_FREED_MEMORY
    /* don't wipe the free list MemoryChunk pointer stored in the chunk */
    wipe_mem((char *) pointer + sizeof(MemoryChunk *),
             slab->chunkSize - sizeof(MemoryChunk *));
#endif
 
    curBlocklistIdx = SlabBlocklistIndex(slab, block->nfree - 1);
    newBlocklistIdx = SlabBlocklistIndex(slab, block->nfree);
 
    /*
     * Check if the block needs to be moved to another element on the
     * blocklist based on it now having 1 more free chunk.
     */
    if (unlikely(curBlocklistIdx != newBlocklistIdx))
    {
        /* do the move */
        dlist_delete_from(&slab->blocklist[curBlocklistIdx], &block->node);
        dlist_push_head(&slab->blocklist[newBlocklistIdx], &block->node);
 
        /*
         * The blocklist[curBlocklistIdx] may now be empty or we may now be
         * able to use a lower-element blocklist.  We'll need to redetermine
         * what the slab->curBlocklistIndex is if the current blocklist was
         * changed or if a lower element one was changed.  We must ensure we
         * use the list with the fullest block(s).
         */
        if (slab->curBlocklistIndex >= curBlocklistIdx)
        {
            slab->curBlocklistIndex = SlabFindNextBlockListIndex(slab);
 
            /*
             * We know there must be a block with at least 1 unused chunk as
             * we just pfree'd one.  Ensure curBlocklistIndex reflects this.
             */
            Assert(slab->curBlocklistIndex > 0);
        }
    }
 
    /* Handle when a block becomes completely empty */
    if (unlikely(block->nfree == slab->chunksPerBlock))
    {
        /* remove the block */
        dlist_delete_from(&slab->blocklist[newBlocklistIdx], &block->node);
 
        /*
         * To avoid thrashing malloc/free, we keep a list of empty blocks that
         * we can reuse again instead of having to malloc a new one.
         */
        if (dclist_count(&slab->emptyblocks) < SLAB_MAXIMUM_EMPTY_BLOCKS)
            dclist_push_head(&slab->emptyblocks, &block->node);
        else
        {
            /*
             * When we have enough empty blocks stored already, we actually
             * free the block.
             */
#ifdef CLOBBER_FREED_MEMORY
            wipe_mem(block, slab->blockSize);
#endif
            free(block);
            slab->header.mem_allocated -= slab->blockSize;
        }
 
        /*
         * Check if we need to reset the blocklist index.  This is required
         * when the blocklist this block is on has become completely empty.
         */
        if (slab->curBlocklistIndex == newBlocklistIdx &&
            dlist_is_empty(&slab->blocklist[newBlocklistIdx]))
            slab->curBlocklistIndex = SlabFindNextBlockListIndex(slab);
    }
}

References Assert(), SlabContext::blocklist, SlabContext::blockSize, SlabContext::chunkSize, SlabContext::chunksPerBlock, SlabContext::curBlocklistIndex, dclist_count(), dclist_push_head(), dlist_delete_from(), dlist_is_empty(), dlist_push_head(), elog(), SlabContext::emptyblocks, free, SlabBlock::freehead, SlabContext::fullChunkSize, SlabContext::header, MemoryContextData::mem_allocated, MemoryChunkGetBlock(), MemoryContextData::name, SlabBlock::nfree, SlabBlock::node, PointerGetMemoryChunk, SlabBlock::slab, Slab_CHUNKHDRSZ, SLAB_MAXIMUM_EMPTY_BLOCKS, SlabBlockIsValid, SlabBlocklistIndex(), SlabFindNextBlockListIndex(), unlikely, VALGRIND_MAKE_MEM_DEFINED, and WARNING.

SlabGetChunkContext()

MemoryContext SlabGetChunkContext

(

void *

pointer

)

Definition at line 810 of file slab.c.

{
    MemoryChunk *chunk = PointerGetMemoryChunk(pointer);
    SlabBlock  *block;
 
    /* Allow access to the chunk header. */
    VALGRIND_MAKE_MEM_DEFINED(chunk, Slab_CHUNKHDRSZ);
 
    block = MemoryChunkGetBlock(chunk);
 
    /* Disallow access to the chunk header. */
    VALGRIND_MAKE_MEM_NOACCESS(chunk, Slab_CHUNKHDRSZ);
 
    Assert(SlabBlockIsValid(block));
 
    return &block->slab->header;
}

References Assert(), SlabContext::header, MemoryChunkGetBlock(), PointerGetMemoryChunk, SlabBlock::slab, Slab_CHUNKHDRSZ, SlabBlockIsValid, VALGRIND_MAKE_MEM_DEFINED, and VALGRIND_MAKE_MEM_NOACCESS.

SlabGetChunkSpace()

Size SlabGetChunkSpace

(

void *

pointer

)

Definition at line 834 of file slab.c.

{
    MemoryChunk *chunk = PointerGetMemoryChunk(pointer);
    SlabBlock  *block;
    SlabContext *slab;
 
    /* Allow access to the chunk header. */
    VALGRIND_MAKE_MEM_DEFINED(chunk, Slab_CHUNKHDRSZ);
 
    block = MemoryChunkGetBlock(chunk);
 
    /* Disallow access to the chunk header. */
    VALGRIND_MAKE_MEM_NOACCESS(chunk, Slab_CHUNKHDRSZ);
 
    Assert(SlabBlockIsValid(block));
    slab = block->slab;
 
    return slab->fullChunkSize;
}

References Assert(), SlabContext::fullChunkSize, MemoryChunkGetBlock(), PointerGetMemoryChunk, SlabBlock::slab, Slab_CHUNKHDRSZ, SlabBlockIsValid, VALGRIND_MAKE_MEM_DEFINED, and VALGRIND_MAKE_MEM_NOACCESS.

SlabGetNextFreeChunk()

static MemoryChunk* SlabGetNextFreeChunk ( SlabContext *  slab, SlabBlock *  block  )

inlinestatic

Definition at line 271 of file slab.c.

{
    MemoryChunk *chunk;
 
    Assert(block->nfree > 0);
 
    if (block->freehead != NULL)
    {
        chunk = block->freehead;
 
        /*
         * Pop the chunk from the linked list of free chunks.  The pointer to
         * the next free chunk is stored in the chunk itself.
         */
        VALGRIND_MAKE_MEM_DEFINED(SlabChunkGetPointer(chunk), sizeof(MemoryChunk *));
        block->freehead = *(MemoryChunk **) SlabChunkGetPointer(chunk);
 
        /* check nothing stomped on the free chunk's memory */
        Assert(block->freehead == NULL ||
               (block->freehead >= SlabBlockGetChunk(slab, block, 0) &&
                block->freehead <= SlabBlockGetChunk(slab, block, slab->chunksPerBlock - 1) &&
                SlabChunkMod(slab, block, block->freehead) == 0));
    }
    else
    {
        Assert(block->nunused > 0);
 
        chunk = block->unused;
        block->unused = (MemoryChunk *) (((char *) block->unused) + slab->fullChunkSize);
        block->nunused--;
    }
 
    block->nfree--;
 
    return chunk;
}

References Assert(), SlabContext::chunksPerBlock, SlabBlock::freehead, SlabContext::fullChunkSize, SlabBlock::nfree, SlabBlock::nunused, SlabBlockGetChunk, SlabChunkGetPointer, SlabBlock::unused, and VALGRIND_MAKE_MEM_DEFINED.

Referenced by SlabAlloc().

SlabIsEmpty()

bool SlabIsEmpty

(

MemoryContext

context

)

Definition at line 859 of file slab.c.

{
    Assert(SlabIsValid((SlabContext *) context));
 
    return (context->mem_allocated == 0);
}

References Assert(), MemoryContextData::mem_allocated, and SlabIsValid.

SlabRealloc()

void* SlabRealloc	(	void *	pointer,
		Size	size
	)

Definition at line 773 of file slab.c.

{
    MemoryChunk *chunk = PointerGetMemoryChunk(pointer);
    SlabBlock  *block;
    SlabContext *slab;
 
    /* Allow access to the chunk header. */
    VALGRIND_MAKE_MEM_DEFINED(chunk, Slab_CHUNKHDRSZ);
 
    block = MemoryChunkGetBlock(chunk);
 
    /* Disallow access to the chunk header. */
    VALGRIND_MAKE_MEM_NOACCESS(chunk, Slab_CHUNKHDRSZ);
 
    /*
     * Try to verify that we have a sane block pointer: the block header
     * should reference a slab context.  (We use a test-and-elog, not just
     * Assert, because it seems highly likely that we're here in error in the
     * first place.)
     */
    if (!SlabBlockIsValid(block))
        elog(ERROR, "could not find block containing chunk %p", chunk);
    slab = block->slab;
 
    /* can't do actual realloc with slab, but let's try to be gentle */
    if (size == slab->chunkSize)
        return pointer;
 
    elog(ERROR, "slab allocator does not support realloc()");
    return NULL;                /* keep compiler quiet */
}

References SlabContext::chunkSize, elog(), ERROR, MemoryChunkGetBlock(), PointerGetMemoryChunk, SlabBlock::slab, Slab_CHUNKHDRSZ, SlabBlockIsValid, VALGRIND_MAKE_MEM_DEFINED, and VALGRIND_MAKE_MEM_NOACCESS.

SlabReset()

void SlabReset

(

MemoryContext

context

)

Definition at line 431 of file slab.c.

{
    SlabContext *slab = (SlabContext *) context;
    dlist_mutable_iter miter;
    int         i;
 
    Assert(SlabIsValid(slab));
 
#ifdef MEMORY_CONTEXT_CHECKING
    /* Check for corruption and leaks before freeing */
    SlabCheck(context);
#endif
 
    /* release any retained empty blocks */
    dclist_foreach_modify(miter, &slab->emptyblocks)
    {
        SlabBlock  *block = dlist_container(SlabBlock, node, miter.cur);
 
        dclist_delete_from(&slab->emptyblocks, miter.cur);
 
#ifdef CLOBBER_FREED_MEMORY
        wipe_mem(block, slab->blockSize);
#endif
        free(block);
        context->mem_allocated -= slab->blockSize;
    }
 
    /* walk over blocklist and free the blocks */
    for (i = 0; i < SLAB_BLOCKLIST_COUNT; i++)
    {
        dlist_foreach_modify(miter, &slab->blocklist[i])
        {
            SlabBlock  *block = dlist_container(SlabBlock, node, miter.cur);
 
            dlist_delete(miter.cur);
 
#ifdef CLOBBER_FREED_MEMORY
            wipe_mem(block, slab->blockSize);
#endif
            free(block);
            context->mem_allocated -= slab->blockSize;
        }
    }
 
    slab->curBlocklistIndex = 0;
 
    Assert(context->mem_allocated == 0);
}

References Assert(), SlabContext::blocklist, SlabContext::blockSize, dlist_mutable_iter::cur, SlabContext::curBlocklistIndex, dclist_delete_from(), dclist_foreach_modify, dlist_container, dlist_delete(), dlist_foreach_modify, SlabContext::emptyblocks, free, i, MemoryContextData::mem_allocated, SLAB_BLOCKLIST_COUNT, and SlabIsValid.

Referenced by SlabDelete().

SlabStats()

void SlabStats	(	MemoryContext	context,
		MemoryStatsPrintFunc	printfunc,
		void *	passthru,
		MemoryContextCounters *	totals,
		bool	print_to_stderr
	)

Definition at line 876 of file slab.c.

{
    SlabContext *slab = (SlabContext *) context;
    Size        nblocks = 0;
    Size        freechunks = 0;
    Size        totalspace;
    Size        freespace = 0;
    int         i;
 
    Assert(SlabIsValid(slab));
 
    /* Include context header in totalspace */
    totalspace = Slab_CONTEXT_HDRSZ(slab->chunksPerBlock);
 
    /* Add the space consumed by blocks in the emptyblocks list */
    totalspace += dclist_count(&slab->emptyblocks) * slab->blockSize;
 
    for (i = 0; i < SLAB_BLOCKLIST_COUNT; i++)
    {
        dlist_iter  iter;
 
        dlist_foreach(iter, &slab->blocklist[i])
        {
            SlabBlock  *block = dlist_container(SlabBlock, node, iter.cur);
 
            nblocks++;
            totalspace += slab->blockSize;
            freespace += slab->fullChunkSize * block->nfree;
            freechunks += block->nfree;
        }
    }
 
    if (printfunc)
    {
        char        stats_string[200];
 
        /* XXX should we include free chunks on empty blocks? */
        snprintf(stats_string, sizeof(stats_string),
                 "%zu total in %zu blocks; %u empty blocks; %zu free (%zu chunks); %zu used",
                 totalspace, nblocks, dclist_count(&slab->emptyblocks),
                 freespace, freechunks, totalspace - freespace);
        printfunc(context, passthru, stats_string, print_to_stderr);
    }
 
    if (totals)
    {
        totals->nblocks += nblocks;
        totals->freechunks += freechunks;
        totals->totalspace += totalspace;
        totals->freespace += freespace;
    }
}

References Assert(), SlabContext::blocklist, SlabContext::blockSize, SlabContext::chunksPerBlock, dlist_iter::cur, dclist_count(), dlist_container, dlist_foreach, SlabContext::emptyblocks, MemoryContextCounters::freechunks, MemoryContextCounters::freespace, SlabContext::fullChunkSize, i, MemoryContextCounters::nblocks, SlabBlock::nfree, SLAB_BLOCKLIST_COUNT, Slab_CONTEXT_HDRSZ, SlabIsValid, snprintf, and MemoryContextCounters::totalspace.