localbuf.c File Reference

#include "postgres.h"
#include "access/parallel.h"
#include "catalog/catalog.h"
#include "executor/instrument.h"
#include "storage/buf_internals.h"
#include "storage/bufmgr.h"
#include "utils/guc.h"
#include "utils/memutils.h"
#include "utils/resowner_private.h"

Include dependency graph for localbuf.c:

Go to the source code of this file.

Data Structures
struct	LocalBufferLookupEnt

Macros
#define	LocalBufHdrGetBlock(bufHdr)   LocalBufferBlockPointers[-((bufHdr)->buf_id + 2)]

Functions
static void	InitLocalBuffers (void)
static Block	GetLocalBufferStorage (void)
PrefetchBufferResult	PrefetchLocalBuffer (SMgrRelation smgr, ForkNumber forkNum, BlockNumber blockNum)
BufferDesc *	LocalBufferAlloc (SMgrRelation smgr, ForkNumber forkNum, BlockNumber blockNum, bool *foundPtr)
void	MarkLocalBufferDirty (Buffer buffer)
void	DropRelFileNodeLocalBuffers (RelFileNode rnode, ForkNumber forkNum, BlockNumber firstDelBlock)
void	DropRelFileNodeAllLocalBuffers (RelFileNode rnode)
static void	CheckForLocalBufferLeaks (void)
void	AtEOXact_LocalBuffers (bool isCommit)
void	AtProcExit_LocalBuffers (void)

Variables
int	NLocBuffer = 0
BufferDesc *	LocalBufferDescriptors = NULL
Block *	LocalBufferBlockPointers = NULL
int32 *	LocalRefCount = NULL
static int	nextFreeLocalBuf = 0
static HTAB *	LocalBufHash = NULL

Macro Definition Documentation

LocalBufHdrGetBlock

#define LocalBufHdrGetBlock

(

bufHdr

)

LocalBufferBlockPointers[-((bufHdr)->buf_id + 2)]

Definition at line 38 of file localbuf.c.

Referenced by LocalBufferAlloc().

Function Documentation

AtEOXact_LocalBuffers()

void AtEOXact_LocalBuffers

(

bool

isCommit

)

Definition at line 577 of file localbuf.c.

References CheckForLocalBufferLeaks().

Referenced by AtEOXact_Buffers().

{
    CheckForLocalBufferLeaks();
}

AtProcExit_LocalBuffers()

void AtProcExit_LocalBuffers

(

void

)

Definition at line 588 of file localbuf.c.

References CheckForLocalBufferLeaks().

Referenced by AtProcExit_Buffers().

{
    /*
     * We shouldn't be holding any remaining pins; if we are, and assertions
     * aren't enabled, we'll fail later in DropRelFileNodeBuffers while trying
     * to drop the temp rels.
     */
    CheckForLocalBufferLeaks();
}

CheckForLocalBufferLeaks()

static void CheckForLocalBufferLeaks ( void  )

static

Definition at line 548 of file localbuf.c.

References Assert, i, LocalRefCount, NLocBuffer, and PrintBufferLeakWarning().

Referenced by AtEOXact_LocalBuffers(), and AtProcExit_LocalBuffers().

{
#ifdef USE_ASSERT_CHECKING
    if (LocalRefCount)
    {
        int         RefCountErrors = 0;
        int         i;

        for (i = 0; i < NLocBuffer; i++)
        {
            if (LocalRefCount[i] != 0)
            {
                Buffer      b = -i - 1;

                PrintBufferLeakWarning(b);
                RefCountErrors++;
            }
        }
        Assert(RefCountErrors == 0);
    }
#endif
}

DropRelFileNodeAllLocalBuffers()

void DropRelFileNodeAllLocalBuffers

(

RelFileNode

rnode

)

Definition at line 373 of file localbuf.c.

References buftag::blockNum, BM_TAG_VALID, BUF_FLAG_MASK, BUF_USAGECOUNT_MASK, CLEAR_BUFFERTAG, elog, ERROR, buftag::forkNum, GetLocalBufferDescriptor, HASH_REMOVE, hash_search(), i, LocalRefCount, MyBackendId, NLocBuffer, pg_atomic_read_u32(), pg_atomic_unlocked_write_u32(), RelFileNodeEquals, relpathbackend, buftag::rnode, BufferDesc::state, and BufferDesc::tag.

Referenced by DropRelFileNodesAllBuffers().

{
    int         i;

    for (i = 0; i < NLocBuffer; i++)
    {
        BufferDesc *bufHdr = GetLocalBufferDescriptor(i);
        LocalBufferLookupEnt *hresult;
        uint32      buf_state;

        buf_state = pg_atomic_read_u32(&bufHdr->state);

        if ((buf_state & BM_TAG_VALID) &&
            RelFileNodeEquals(bufHdr->tag.rnode, rnode))
        {
            if (LocalRefCount[i] != 0)
                elog(ERROR, "block %u of %s is still referenced (local %u)",
                     bufHdr->tag.blockNum,
                     relpathbackend(bufHdr->tag.rnode, MyBackendId,
                                    bufHdr->tag.forkNum),
                     LocalRefCount[i]);
            /* Remove entry from hashtable */
            hresult = (LocalBufferLookupEnt *)
                hash_search(LocalBufHash, (void *) &bufHdr->tag,
                            HASH_REMOVE, NULL);
            if (!hresult)       /* shouldn't happen */
                elog(ERROR, "local buffer hash table corrupted");
            /* Mark buffer invalid */
            CLEAR_BUFFERTAG(bufHdr->tag);
            buf_state &= ~BUF_FLAG_MASK;
            buf_state &= ~BUF_USAGECOUNT_MASK;
            pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
        }
    }
}

DropRelFileNodeLocalBuffers()

void DropRelFileNodeLocalBuffers	(	RelFileNode	rnode,
		ForkNumber	forkNum,
		BlockNumber	firstDelBlock
	)

Definition at line 326 of file localbuf.c.

References buftag::blockNum, BM_TAG_VALID, BUF_FLAG_MASK, BUF_USAGECOUNT_MASK, CLEAR_BUFFERTAG, elog, ERROR, buftag::forkNum, GetLocalBufferDescriptor, HASH_REMOVE, hash_search(), i, LocalRefCount, MyBackendId, NLocBuffer, pg_atomic_read_u32(), pg_atomic_unlocked_write_u32(), RelFileNodeEquals, relpathbackend, buftag::rnode, BufferDesc::state, and BufferDesc::tag.

Referenced by DropRelFileNodeBuffers().

{
    int         i;

    for (i = 0; i < NLocBuffer; i++)
    {
        BufferDesc *bufHdr = GetLocalBufferDescriptor(i);
        LocalBufferLookupEnt *hresult;
        uint32      buf_state;

        buf_state = pg_atomic_read_u32(&bufHdr->state);

        if ((buf_state & BM_TAG_VALID) &&
            RelFileNodeEquals(bufHdr->tag.rnode, rnode) &&
            bufHdr->tag.forkNum == forkNum &&
            bufHdr->tag.blockNum >= firstDelBlock)
        {
            if (LocalRefCount[i] != 0)
                elog(ERROR, "block %u of %s is still referenced (local %u)",
                     bufHdr->tag.blockNum,
                     relpathbackend(bufHdr->tag.rnode, MyBackendId,
                                    bufHdr->tag.forkNum),
                     LocalRefCount[i]);
            /* Remove entry from hashtable */
            hresult = (LocalBufferLookupEnt *)
                hash_search(LocalBufHash, (void *) &bufHdr->tag,
                            HASH_REMOVE, NULL);
            if (!hresult)       /* shouldn't happen */
                elog(ERROR, "local buffer hash table corrupted");
            /* Mark buffer invalid */
            CLEAR_BUFFERTAG(bufHdr->tag);
            buf_state &= ~BUF_FLAG_MASK;
            buf_state &= ~BUF_USAGECOUNT_MASK;
            pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
        }
    }
}

GetLocalBufferStorage()

static Block GetLocalBufferStorage ( void  )

static

Definition at line 493 of file localbuf.c.

References ALLOCSET_DEFAULT_SIZES, AllocSetContextCreate, Assert, Max, MaxAllocSize, MemoryContextAlloc(), Min, NLocBuffer, and TopMemoryContext.

Referenced by LocalBufferAlloc().

{
    static char *cur_block = NULL;
    static int  next_buf_in_block = 0;
    static int  num_bufs_in_block = 0;
    static int  total_bufs_allocated = 0;
    static MemoryContext LocalBufferContext = NULL;

    char       *this_buf;

    Assert(total_bufs_allocated < NLocBuffer);

    if (next_buf_in_block >= num_bufs_in_block)
    {
        /* Need to make a new request to memmgr */
        int         num_bufs;

        /*
         * We allocate local buffers in a context of their own, so that the
         * space eaten for them is easily recognizable in MemoryContextStats
         * output.  Create the context on first use.
         */
        if (LocalBufferContext == NULL)
            LocalBufferContext =
                AllocSetContextCreate(TopMemoryContext,
                                      "LocalBufferContext",
                                      ALLOCSET_DEFAULT_SIZES);

        /* Start with a 16-buffer request; subsequent ones double each time */
        num_bufs = Max(num_bufs_in_block * 2, 16);
        /* But not more than what we need for all remaining local bufs */
        num_bufs = Min(num_bufs, NLocBuffer - total_bufs_allocated);
        /* And don't overflow MaxAllocSize, either */
        num_bufs = Min(num_bufs, MaxAllocSize / BLCKSZ);

        cur_block = (char *) MemoryContextAlloc(LocalBufferContext,
                                                num_bufs * BLCKSZ);
        next_buf_in_block = 0;
        num_bufs_in_block = num_bufs;
    }

    /* Allocate next buffer in current memory block */
    this_buf = cur_block + next_buf_in_block * BLCKSZ;
    next_buf_in_block++;
    total_bufs_allocated++;

    return (Block) this_buf;
}

InitLocalBuffers()

static void InitLocalBuffers ( void  )

static

Definition at line 416 of file localbuf.c.

References buf, BufferDesc::buf_id, calloc, elog, HASHCTL::entrysize, ereport, errcode(), errmsg(), ERROR, FATAL, GetLocalBufferDescriptor, HASH_BLOBS, hash_create(), HASH_ELEM, i, IsParallelWorker, HASHCTL::keysize, LocalBufferBlockPointers, LocalRefCount, nextFreeLocalBuf, NLocBuffer, and num_temp_buffers.

Referenced by LocalBufferAlloc(), and PrefetchLocalBuffer().

{
    int         nbufs = num_temp_buffers;
    HASHCTL     info;
    int         i;

    /*
     * Parallel workers can't access data in temporary tables, because they
     * have no visibility into the local buffers of their leader.  This is a
     * convenient, low-cost place to provide a backstop check for that.  Note
     * that we don't wish to prevent a parallel worker from accessing catalog
     * metadata about a temp table, so checks at higher levels would be
     * inappropriate.
     */
    if (IsParallelWorker())
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_TRANSACTION_STATE),
                 errmsg("cannot access temporary tables during a parallel operation")));

    /* Allocate and zero buffer headers and auxiliary arrays */
    LocalBufferDescriptors = (BufferDesc *) calloc(nbufs, sizeof(BufferDesc));
    LocalBufferBlockPointers = (Block *) calloc(nbufs, sizeof(Block));
    LocalRefCount = (int32 *) calloc(nbufs, sizeof(int32));
    if (!LocalBufferDescriptors || !LocalBufferBlockPointers || !LocalRefCount)
        ereport(FATAL,
                (errcode(ERRCODE_OUT_OF_MEMORY),
                 errmsg("out of memory")));

    nextFreeLocalBuf = 0;

    /* initialize fields that need to start off nonzero */
    for (i = 0; i < nbufs; i++)
    {
        BufferDesc *buf = GetLocalBufferDescriptor(i);

        /*
         * negative to indicate local buffer. This is tricky: shared buffers
         * start with 0. We have to start with -2. (Note that the routine
         * BufferDescriptorGetBuffer adds 1 to buf_id so our first buffer id
         * is -1.)
         */
        buf->buf_id = -i - 2;

        /*
         * Intentionally do not initialize the buffer's atomic variable
         * (besides zeroing the underlying memory above). That way we get
         * errors on platforms without atomics, if somebody (re-)introduces
         * atomic operations for local buffers.
         */
    }

    /* Create the lookup hash table */
    info.keysize = sizeof(BufferTag);
    info.entrysize = sizeof(LocalBufferLookupEnt);

    LocalBufHash = hash_create("Local Buffer Lookup Table",
                               nbufs,
                               &info,
                               HASH_ELEM | HASH_BLOBS);

    if (!LocalBufHash)
        elog(ERROR, "could not initialize local buffer hash table");

    /* Initialization done, mark buffers allocated */
    NLocBuffer = nbufs;
}

LocalBufferAlloc()

BufferDesc* LocalBufferAlloc	(	SMgrRelation	smgr,
		ForkNumber	forkNum,
		BlockNumber	blockNum,
		bool *	foundPtr
	)

Definition at line 109 of file localbuf.c.

References Assert, buftag::blockNum, BM_DIRTY, BM_IO_ERROR, BM_JUST_DIRTIED, BM_MAX_USAGE_COUNT, BM_TAG_VALID, BM_VALID, BUF_STATE_GET_USAGECOUNT, BUF_USAGECOUNT_MASK, BUF_USAGECOUNT_ONE, BufferDescriptorGetBuffer, BUFFERTAGS_EQUAL, CLEAR_BUFFERTAG, CurrentResourceOwner, elog, ereport, errcode(), errmsg(), ERROR, buftag::forkNum, fprintf, GetLocalBufferDescriptor, GetLocalBufferStorage(), HASH_ENTER, HASH_FIND, HASH_REMOVE, hash_search(), LocalBufferLookupEnt::id, INIT_BUFFERTAG, InitLocalBuffers(), BufferUsage::local_blks_written, LocalBufHdrGetBlock, LocalRefCount, MyBackendId, nextFreeLocalBuf, NLocBuffer, RelFileNodeBackend::node, PageSetChecksumInplace(), pg_atomic_read_u32(), pg_atomic_unlocked_write_u32(), pgBufferUsage, RelFileNode::relNode, ResourceOwnerRememberBuffer(), buftag::rnode, SMgrRelationData::smgr_rnode, smgropen(), smgrwrite(), BufferDesc::state, and BufferDesc::tag.

Referenced by ReadBuffer_common().

{
    BufferTag   newTag;         /* identity of requested block */
    LocalBufferLookupEnt *hresult;
    BufferDesc *bufHdr;
    int         b;
    int         trycounter;
    bool        found;
    uint32      buf_state;

    INIT_BUFFERTAG(newTag, smgr->smgr_rnode.node, forkNum, blockNum);

    /* Initialize local buffers if first request in this session */
    if (LocalBufHash == NULL)
        InitLocalBuffers();

    /* See if the desired buffer already exists */
    hresult = (LocalBufferLookupEnt *)
        hash_search(LocalBufHash, (void *) &newTag, HASH_FIND, NULL);

    if (hresult)
    {
        b = hresult->id;
        bufHdr = GetLocalBufferDescriptor(b);
        Assert(BUFFERTAGS_EQUAL(bufHdr->tag, newTag));
#ifdef LBDEBUG
        fprintf(stderr, "LB ALLOC (%u,%d,%d) %d\n",
                smgr->smgr_rnode.node.relNode, forkNum, blockNum, -b - 1);
#endif
        buf_state = pg_atomic_read_u32(&bufHdr->state);

        /* this part is equivalent to PinBuffer for a shared buffer */
        if (LocalRefCount[b] == 0)
        {
            if (BUF_STATE_GET_USAGECOUNT(buf_state) < BM_MAX_USAGE_COUNT)
            {
                buf_state += BUF_USAGECOUNT_ONE;
                pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
            }
        }
        LocalRefCount[b]++;
        ResourceOwnerRememberBuffer(CurrentResourceOwner,
                                    BufferDescriptorGetBuffer(bufHdr));
        if (buf_state & BM_VALID)
            *foundPtr = true;
        else
        {
            /* Previous read attempt must have failed; try again */
            *foundPtr = false;
        }
        return bufHdr;
    }

#ifdef LBDEBUG
    fprintf(stderr, "LB ALLOC (%u,%d,%d) %d\n",
            smgr->smgr_rnode.node.relNode, forkNum, blockNum,
            -nextFreeLocalBuf - 1);
#endif

    /*
     * Need to get a new buffer.  We use a clock sweep algorithm (essentially
     * the same as what freelist.c does now...)
     */
    trycounter = NLocBuffer;
    for (;;)
    {
        b = nextFreeLocalBuf;

        if (++nextFreeLocalBuf >= NLocBuffer)
            nextFreeLocalBuf = 0;

        bufHdr = GetLocalBufferDescriptor(b);

        if (LocalRefCount[b] == 0)
        {
            buf_state = pg_atomic_read_u32(&bufHdr->state);

            if (BUF_STATE_GET_USAGECOUNT(buf_state) > 0)
            {
                buf_state -= BUF_USAGECOUNT_ONE;
                pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
                trycounter = NLocBuffer;
            }
            else
            {
                /* Found a usable buffer */
                LocalRefCount[b]++;
                ResourceOwnerRememberBuffer(CurrentResourceOwner,
                                            BufferDescriptorGetBuffer(bufHdr));
                break;
            }
        }
        else if (--trycounter == 0)
            ereport(ERROR,
                    (errcode(ERRCODE_INSUFFICIENT_RESOURCES),
                     errmsg("no empty local buffer available")));
    }

    /*
     * this buffer is not referenced but it might still be dirty. if that's
     * the case, write it out before reusing it!
     */
    if (buf_state & BM_DIRTY)
    {
        SMgrRelation oreln;
        Page        localpage = (char *) LocalBufHdrGetBlock(bufHdr);

        /* Find smgr relation for buffer */
        oreln = smgropen(bufHdr->tag.rnode, MyBackendId);

        PageSetChecksumInplace(localpage, bufHdr->tag.blockNum);

        /* And write... */
        smgrwrite(oreln,
                  bufHdr->tag.forkNum,
                  bufHdr->tag.blockNum,
                  localpage,
                  false);

        /* Mark not-dirty now in case we error out below */
        buf_state &= ~BM_DIRTY;
        pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);

        pgBufferUsage.local_blks_written++;
    }

    /*
     * lazy memory allocation: allocate space on first use of a buffer.
     */
    if (LocalBufHdrGetBlock(bufHdr) == NULL)
    {
        /* Set pointer for use by BufferGetBlock() macro */
        LocalBufHdrGetBlock(bufHdr) = GetLocalBufferStorage();
    }

    /*
     * Update the hash table: remove old entry, if any, and make new one.
     */
    if (buf_state & BM_TAG_VALID)
    {
        hresult = (LocalBufferLookupEnt *)
            hash_search(LocalBufHash, (void *) &bufHdr->tag,
                        HASH_REMOVE, NULL);
        if (!hresult)           /* shouldn't happen */
            elog(ERROR, "local buffer hash table corrupted");
        /* mark buffer invalid just in case hash insert fails */
        CLEAR_BUFFERTAG(bufHdr->tag);
        buf_state &= ~(BM_VALID | BM_TAG_VALID);
        pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
    }

    hresult = (LocalBufferLookupEnt *)
        hash_search(LocalBufHash, (void *) &newTag, HASH_ENTER, &found);
    if (found)                  /* shouldn't happen */
        elog(ERROR, "local buffer hash table corrupted");
    hresult->id = b;

    /*
     * it's all ours now.
     */
    bufHdr->tag = newTag;
    buf_state &= ~(BM_VALID | BM_DIRTY | BM_JUST_DIRTIED | BM_IO_ERROR);
    buf_state |= BM_TAG_VALID;
    buf_state &= ~BUF_USAGECOUNT_MASK;
    buf_state += BUF_USAGECOUNT_ONE;
    pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);

    *foundPtr = false;
    return bufHdr;
}

MarkLocalBufferDirty()

void MarkLocalBufferDirty

(

Buffer

buffer

)

Definition at line 286 of file localbuf.c.

References Assert, BM_DIRTY, BufferIsLocal, fprintf, GetLocalBufferDescriptor, BufferUsage::local_blks_dirtied, LocalRefCount, pg_atomic_read_u32(), pg_atomic_unlocked_write_u32(), pgBufferUsage, and BufferDesc::state.

Referenced by MarkBufferDirty(), and MarkBufferDirtyHint().

{
    int         bufid;
    BufferDesc *bufHdr;
    uint32      buf_state;

    Assert(BufferIsLocal(buffer));

#ifdef LBDEBUG
    fprintf(stderr, "LB DIRTY %d\n", buffer);
#endif

    bufid = -(buffer + 1);

    Assert(LocalRefCount[bufid] > 0);

    bufHdr = GetLocalBufferDescriptor(bufid);

    buf_state = pg_atomic_read_u32(&bufHdr->state);

    if (!(buf_state & BM_DIRTY))
        pgBufferUsage.local_blks_dirtied++;

    buf_state |= BM_DIRTY;

    pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
}

PrefetchLocalBuffer()

PrefetchBufferResult PrefetchLocalBuffer	(	SMgrRelation	smgr,
		ForkNumber	forkNum,
		BlockNumber	blockNum
	)

Definition at line 64 of file localbuf.c.

References HASH_FIND, hash_search(), LocalBufferLookupEnt::id, INIT_BUFFERTAG, PrefetchBufferResult::initiated_io, InitLocalBuffers(), InvalidBuffer, RelFileNodeBackend::node, PrefetchBufferResult::recent_buffer, SMgrRelationData::smgr_rnode, and smgrprefetch().

Referenced by PrefetchBuffer().

{
    PrefetchBufferResult result = {InvalidBuffer, false};
    BufferTag   newTag;         /* identity of requested block */
    LocalBufferLookupEnt *hresult;

    INIT_BUFFERTAG(newTag, smgr->smgr_rnode.node, forkNum, blockNum);

    /* Initialize local buffers if first request in this session */
    if (LocalBufHash == NULL)
        InitLocalBuffers();

    /* See if the desired buffer already exists */
    hresult = (LocalBufferLookupEnt *)
        hash_search(LocalBufHash, (void *) &newTag, HASH_FIND, NULL);

    if (hresult)
    {
        /* Yes, so nothing to do */
        result.recent_buffer = -hresult->id - 1;
    }
    else
    {
#ifdef USE_PREFETCH
        /* Not in buffers, so initiate prefetch */
        smgrprefetch(smgr, forkNum, blockNum);
        result.initiated_io = true;
#endif                          /* USE_PREFETCH */
    }

    return result;
}

Variable Documentation

LocalBufferBlockPointers

Block* LocalBufferBlockPointers = NULL

Definition at line 44 of file localbuf.c.

Referenced by InitLocalBuffers().

LocalBufferDescriptors

BufferDesc* LocalBufferDescriptors = NULL

Definition at line 43 of file localbuf.c.

LocalBufHash

HTAB* LocalBufHash = NULL

static

Definition at line 49 of file localbuf.c.

LocalRefCount

int32* LocalRefCount = NULL

Definition at line 45 of file localbuf.c.

Referenced by CheckForLocalBufferLeaks(), ConditionalLockBufferForCleanup(), DropRelFileNodeAllLocalBuffers(), DropRelFileNodeLocalBuffers(), IncrBufferRefCount(), InitLocalBuffers(), IsBufferCleanupOK(), LocalBufferAlloc(), LockBufferForCleanup(), MarkLocalBufferDirty(), PrintBufferLeakWarning(), ReleaseAndReadBuffer(), and ReleaseBuffer().

nextFreeLocalBuf

int nextFreeLocalBuf = 0

static

Definition at line 47 of file localbuf.c.

Referenced by InitLocalBuffers(), and LocalBufferAlloc().

NLocBuffer

int NLocBuffer = 0

Definition at line 41 of file localbuf.c.

Referenced by check_temp_buffers(), CheckForLocalBufferLeaks(), DropRelFileNodeAllLocalBuffers(), DropRelFileNodeLocalBuffers(), FlushRelationBuffers(), GetLocalBufferStorage(), hashbuild(), InitLocalBuffers(), and LocalBufferAlloc().