sinvaladt.h File Reference

#include "storage/sinval.h"

Include dependency graph for sinvaladt.h:

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Go to the source code of this file.

Functions
void	SharedInvalBackendInit (bool sendOnly)
void	SIInsertDataEntries (const SharedInvalidationMessage *data, int n)
int	SIGetDataEntries (SharedInvalidationMessage *data, int datasize)
void	SICleanupQueue (bool callerHasWriteLock, int minFree)
LocalTransactionId	GetNextLocalTransactionId (void)

Function Documentation

GetNextLocalTransactionId()

LocalTransactionId GetNextLocalTransactionId ( void  )

extern

Definition at line 703 of file sinvaladt.c.

{
    LocalTransactionId result;
 
    /* loop to avoid returning InvalidLocalTransactionId at wraparound */
    do
    {
        result = nextLocalTransactionId++;
    } while (!LocalTransactionIdIsValid(result));
 
    return result;
}

References LocalTransactionIdIsValid, nextLocalTransactionId, and result.

Referenced by InitRecoveryTransactionEnvironment(), and StartTransaction().

SharedInvalBackendInit()

void SharedInvalBackendInit ( bool  sendOnly )

extern

Definition at line 274 of file sinvaladt.c.

{
    ProcState  *stateP;
    pid_t       oldPid;
    SISeg      *segP = shmInvalBuffer;
 
    if (MyProcNumber < 0)
        elog(ERROR, "MyProcNumber not set");
    if (MyProcNumber >= NumProcStateSlots)
        elog(PANIC, "unexpected MyProcNumber %d in SharedInvalBackendInit (max %d)",
             MyProcNumber, NumProcStateSlots);
    stateP = &segP->procState[MyProcNumber];
 
    /*
     * This can run in parallel with read operations, but not with write
     * operations, since SIInsertDataEntries relies on the pgprocnos array to
     * set hasMessages appropriately.
     */
    LWLockAcquire(SInvalWriteLock, LW_EXCLUSIVE);
 
    oldPid = stateP->procPid;
    if (oldPid != 0)
    {
        LWLockRelease(SInvalWriteLock);
        elog(ERROR, "sinval slot for backend %d is already in use by process %d",
             MyProcNumber, (int) oldPid);
    }
 
    shmInvalBuffer->pgprocnos[shmInvalBuffer->numProcs++] = MyProcNumber;
 
    /* Fetch next local transaction ID into local memory */
    nextLocalTransactionId = stateP->nextLXID;
 
    /* mark myself active, with all extant messages already read */
    stateP->procPid = MyProcPid;
    stateP->nextMsgNum = segP->maxMsgNum;
    stateP->resetState = false;
    stateP->signaled = false;
    stateP->hasMessages = false;
    stateP->sendOnly = sendOnly;
 
    LWLockRelease(SInvalWriteLock);
 
    /* register exit routine to mark my entry inactive at exit */
    on_shmem_exit(CleanupInvalidationState, PointerGetDatum(segP));
}

References CleanupInvalidationState(), elog, ERROR, fb(), LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MyProcNumber, MyProcPid, nextLocalTransactionId, SISeg::numProcs, NumProcStateSlots, on_shmem_exit(), PANIC, SISeg::pgprocnos, PointerGetDatum(), and shmInvalBuffer.

Referenced by InitPostgres(), and InitRecoveryTransactionEnvironment().

SICleanupQueue()

void SICleanupQueue ( bool  callerHasWriteLock, int  minFree  )

extern

Definition at line 579 of file sinvaladt.c.

{
    SISeg      *segP = shmInvalBuffer;
    int         min,
                minsig,
                lowbound,
                numMsgs,
                i;
    ProcState  *needSig = NULL;
 
    /* Lock out all writers and readers */
    if (!callerHasWriteLock)
        LWLockAcquire(SInvalWriteLock, LW_EXCLUSIVE);
    LWLockAcquire(SInvalReadLock, LW_EXCLUSIVE);
 
    /*
     * Recompute minMsgNum = minimum of all backends' nextMsgNum, identify the
     * furthest-back backend that needs signaling (if any), and reset any
     * backends that are too far back.  Note that because we ignore sendOnly
     * backends here it is possible for them to keep sending messages without
     * a problem even when they are the only active backend.
     */
    min = segP->maxMsgNum;
    minsig = min - SIG_THRESHOLD;
    lowbound = min - MAXNUMMESSAGES + minFree;
 
    for (i = 0; i < segP->numProcs; i++)
    {
        ProcState  *stateP = &segP->procState[segP->pgprocnos[i]];
        int         n = stateP->nextMsgNum;
 
        /* Ignore if already in reset state */
        Assert(stateP->procPid != 0);
        if (stateP->resetState || stateP->sendOnly)
            continue;
 
        /*
         * If we must free some space and this backend is preventing it, force
         * him into reset state and then ignore until he catches up.
         */
        if (n < lowbound)
        {
            stateP->resetState = true;
            /* no point in signaling him ... */
            continue;
        }
 
        /* Track the global minimum nextMsgNum */
        if (n < min)
            min = n;
 
        /* Also see who's furthest back of the unsignaled backends */
        if (n < minsig && !stateP->signaled)
        {
            minsig = n;
            needSig = stateP;
        }
    }
    segP->minMsgNum = min;
 
    /*
     * When minMsgNum gets really large, decrement all message counters so as
     * to forestall overflow of the counters.  This happens seldom enough that
     * folding it into the previous loop would be a loser.
     */
    if (min >= MSGNUMWRAPAROUND)
    {
        segP->minMsgNum -= MSGNUMWRAPAROUND;
        segP->maxMsgNum -= MSGNUMWRAPAROUND;
        for (i = 0; i < segP->numProcs; i++)
            segP->procState[segP->pgprocnos[i]].nextMsgNum -= MSGNUMWRAPAROUND;
    }
 
    /*
     * Determine how many messages are still in the queue, and set the
     * threshold at which we should repeat SICleanupQueue().
     */
    numMsgs = segP->maxMsgNum - segP->minMsgNum;
    if (numMsgs < CLEANUP_MIN)
        segP->nextThreshold = CLEANUP_MIN;
    else
        segP->nextThreshold = (numMsgs / CLEANUP_QUANTUM + 1) * CLEANUP_QUANTUM;
 
    /*
     * Lastly, signal anyone who needs a catchup interrupt.  Since
     * SendProcSignal() might not be fast, we don't want to hold locks while
     * executing it.
     */
    if (needSig)
    {
        pid_t       his_pid = needSig->procPid;
        ProcNumber  his_procNumber = (needSig - &segP->procState[0]);
 
        needSig->signaled = true;
        LWLockRelease(SInvalReadLock);
        LWLockRelease(SInvalWriteLock);
        elog(DEBUG4, "sending sinval catchup signal to PID %d", (int) his_pid);
        SendProcSignal(his_pid, PROCSIG_CATCHUP_INTERRUPT, his_procNumber);
        if (callerHasWriteLock)
            LWLockAcquire(SInvalWriteLock, LW_EXCLUSIVE);
    }
    else
    {
        LWLockRelease(SInvalReadLock);
        if (!callerHasWriteLock)
            LWLockRelease(SInvalWriteLock);
    }
}

References Assert, CLEANUP_MIN, CLEANUP_QUANTUM, DEBUG4, elog, fb(), i, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MAXNUMMESSAGES, MSGNUMWRAPAROUND, ProcState::nextMsgNum, PROCSIG_CATCHUP_INTERRUPT, SendProcSignal(), shmInvalBuffer, and SIG_THRESHOLD.

Referenced by ReceiveSharedInvalidMessages(), and SIInsertDataEntries().

SIGetDataEntries()

int SIGetDataEntries ( SharedInvalidationMessage *  data, int  datasize  )

extern

Definition at line 475 of file sinvaladt.c.

{
    SISeg      *segP;
    ProcState  *stateP;
    int         max;
    int         n;
 
    segP = shmInvalBuffer;
    stateP = &segP->procState[MyProcNumber];
 
    /*
     * Before starting to take locks, do a quick, unlocked test to see whether
     * there can possibly be anything to read.  On a multiprocessor system,
     * it's possible that this load could migrate backwards and occur before
     * we actually enter this function, so we might miss a sinval message that
     * was just added by some other processor.  But they can't migrate
     * backwards over a preceding lock acquisition, so it should be OK.  If we
     * haven't acquired a lock preventing against further relevant
     * invalidations, any such occurrence is not much different than if the
     * invalidation had arrived slightly later in the first place.
     */
    if (!stateP->hasMessages)
        return 0;
 
    LWLockAcquire(SInvalReadLock, LW_SHARED);
 
    /*
     * We must reset hasMessages before determining how many messages we're
     * going to read.  That way, if new messages arrive after we have
     * determined how many we're reading, the flag will get reset and we'll
     * notice those messages part-way through.
     *
     * Note that, if we don't end up reading all of the messages, we had
     * better be certain to reset this flag before exiting!
     */
    stateP->hasMessages = false;
 
    /* Fetch current value of maxMsgNum using spinlock */
    SpinLockAcquire(&segP->msgnumLock);
    max = segP->maxMsgNum;
    SpinLockRelease(&segP->msgnumLock);
 
    if (stateP->resetState)
    {
        /*
         * Force reset.  We can say we have dealt with any messages added
         * since the reset, as well; and that means we should clear the
         * signaled flag, too.
         */
        stateP->nextMsgNum = max;
        stateP->resetState = false;
        stateP->signaled = false;
        LWLockRelease(SInvalReadLock);
        return -1;
    }
 
    /*
     * Retrieve messages and advance backend's counter, until data array is
     * full or there are no more messages.
     *
     * There may be other backends that haven't read the message(s), so we
     * cannot delete them here.  SICleanupQueue() will eventually remove them
     * from the queue.
     */
    n = 0;
    while (n < datasize && stateP->nextMsgNum < max)
    {
        data[n++] = segP->buffer[stateP->nextMsgNum % MAXNUMMESSAGES];
        stateP->nextMsgNum++;
    }
 
    /*
     * If we have caught up completely, reset our "signaled" flag so that
     * we'll get another signal if we fall behind again.
     *
     * If we haven't caught up completely, reset the hasMessages flag so that
     * we see the remaining messages next time.
     */
    if (stateP->nextMsgNum >= max)
        stateP->signaled = false;
    else
        stateP->hasMessages = true;
 
    LWLockRelease(SInvalReadLock);
    return n;
}

References data, fb(), LW_SHARED, LWLockAcquire(), LWLockRelease(), MAXNUMMESSAGES, MyProcNumber, SISeg::procState, shmInvalBuffer, SpinLockAcquire(), and SpinLockRelease().

Referenced by ReceiveSharedInvalidMessages().

SIInsertDataEntries()

void SIInsertDataEntries ( const SharedInvalidationMessage *  data, int  n  )

extern

Definition at line 372 of file sinvaladt.c.

{
    SISeg      *segP = shmInvalBuffer;
 
    /*
     * N can be arbitrarily large.  We divide the work into groups of no more
     * than WRITE_QUANTUM messages, to be sure that we don't hold the lock for
     * an unreasonably long time.  (This is not so much because we care about
     * letting in other writers, as that some just-caught-up backend might be
     * trying to do SICleanupQueue to pass on its signal, and we don't want it
     * to have to wait a long time.)  Also, we need to consider calling
     * SICleanupQueue every so often.
     */
    while (n > 0)
    {
        int         nthistime = Min(n, WRITE_QUANTUM);
        int         numMsgs;
        int         max;
        int         i;
 
        n -= nthistime;
 
        LWLockAcquire(SInvalWriteLock, LW_EXCLUSIVE);
 
        /*
         * If the buffer is full, we *must* acquire some space.  Clean the
         * queue and reset anyone who is preventing space from being freed.
         * Otherwise, clean the queue only when it's exceeded the next
         * fullness threshold.  We have to loop and recheck the buffer state
         * after any call of SICleanupQueue.
         */
        for (;;)
        {
            numMsgs = segP->maxMsgNum - segP->minMsgNum;
            if (numMsgs + nthistime > MAXNUMMESSAGES ||
                numMsgs >= segP->nextThreshold)
                SICleanupQueue(true, nthistime);
            else
                break;
        }
 
        /*
         * Insert new message(s) into proper slot of circular buffer
         */
        max = segP->maxMsgNum;
        while (nthistime-- > 0)
        {
            segP->buffer[max % MAXNUMMESSAGES] = *data++;
            max++;
        }
 
        /* Update current value of maxMsgNum using spinlock */
        SpinLockAcquire(&segP->msgnumLock);
        segP->maxMsgNum = max;
        SpinLockRelease(&segP->msgnumLock);
 
        /*
         * Now that the maxMsgNum change is globally visible, we give everyone
         * a swift kick to make sure they read the newly added messages.
         * Releasing SInvalWriteLock will enforce a full memory barrier, so
         * these (unlocked) changes will be committed to memory before we exit
         * the function.
         */
        for (i = 0; i < segP->numProcs; i++)
        {
            ProcState  *stateP = &segP->procState[segP->pgprocnos[i]];
 
            stateP->hasMessages = true;
        }
 
        LWLockRelease(SInvalWriteLock);
    }
}

References data, fb(), ProcState::hasMessages, i, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MAXNUMMESSAGES, Min, shmInvalBuffer, SICleanupQueue(), SpinLockAcquire(), SpinLockRelease(), and WRITE_QUANTUM.

Referenced by SendSharedInvalidMessages().