Line data    Source code

       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * sinval.c
       4             :  *    POSTGRES shared cache invalidation communication code.
       5             :  *
       6             :  * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
       7             :  * Portions Copyright (c) 1994, Regents of the University of California
       8             :  *
       9             :  *
      10             :  * IDENTIFICATION
      11             :  *    src/backend/storage/ipc/sinval.c
      12             :  *
      13             :  *-------------------------------------------------------------------------
      14             :  */
      15             : #include "postgres.h"
      16             : 
      17             : #include "access/xact.h"
      18             : #include "miscadmin.h"
      19             : #include "storage/latch.h"
      20             : #include "storage/sinvaladt.h"
      21             : #include "utils/inval.h"
      22             : 
      23             : 
      24             : uint64      SharedInvalidMessageCounter;
      25             : 
      26             : 
      27             : /*
      28             :  * Because backends sitting idle will not be reading sinval events, we
      29             :  * need a way to give an idle backend a swift kick in the rear and make
      30             :  * it catch up before the sinval queue overflows and forces it to go
      31             :  * through a cache reset exercise.  This is done by sending
      32             :  * PROCSIG_CATCHUP_INTERRUPT to any backend that gets too far behind.
      33             :  *
      34             :  * The signal handler will set an interrupt pending flag and will set the
      35             :  * processes latch. Whenever starting to read from the client, or when
      36             :  * interrupted while doing so, ProcessClientReadInterrupt() will call
      37             :  * ProcessCatchupEvent().
      38             :  */
      39             : volatile sig_atomic_t catchupInterruptPending = false;
      40             : 
      41             : 
      42             : /*
      43             :  * SendSharedInvalidMessages
      44             :  *  Add shared-cache-invalidation message(s) to the global SI message queue.
      45             :  */
      46             : void
      47      783312 : SendSharedInvalidMessages(const SharedInvalidationMessage *msgs, int n)
      48             : {
      49      783312 :     SIInsertDataEntries(msgs, n);
      50      783312 : }
      51             : 
      52             : /*
      53             :  * ReceiveSharedInvalidMessages
      54             :  *      Process shared-cache-invalidation messages waiting for this backend
      55             :  *
      56             :  * We guarantee to process all messages that had been queued before the
      57             :  * routine was entered.  It is of course possible for more messages to get
      58             :  * queued right after our last SIGetDataEntries call.
      59             :  *
      60             :  * NOTE: it is entirely possible for this routine to be invoked recursively
      61             :  * as a consequence of processing inside the invalFunction or resetFunction.
      62             :  * Furthermore, such a recursive call must guarantee that all outstanding
      63             :  * inval messages have been processed before it exits.  This is the reason
      64             :  * for the strange-looking choice to use a statically allocated buffer array
      65             :  * and counters; it's so that a recursive call can process messages already
      66             :  * sucked out of sinvaladt.c.
      67             :  */
      68             : void
      69    31514800 : ReceiveSharedInvalidMessages(void (*invalFunction) (SharedInvalidationMessage *msg),
      70             :                              void (*resetFunction) (void))
      71             : {
      72             : #define MAXINVALMSGS 32
      73             :     static SharedInvalidationMessage messages[MAXINVALMSGS];
      74             : 
      75             :     /*
      76             :      * We use volatile here to prevent bugs if a compiler doesn't realize that
      77             :      * recursion is a possibility ...
      78             :      */
      79             :     static volatile int nextmsg = 0;
      80             :     static volatile int nummsgs = 0;
      81             : 
      82             :     /* Deal with any messages still pending from an outer recursion */
      83    31516722 :     while (nextmsg < nummsgs)
      84             :     {
      85        1990 :         SharedInvalidationMessage msg = messages[nextmsg++];
      86             : 
      87        1990 :         SharedInvalidMessageCounter++;
      88        1990 :         invalFunction(&msg);
      89             :     }
      90             : 
      91             :     do
      92             :     {
      93             :         int         getResult;
      94             : 
      95    32240978 :         nextmsg = nummsgs = 0;
      96             : 
      97             :         /* Try to get some more messages */
      98    32240978 :         getResult = SIGetDataEntries(messages, MAXINVALMSGS);
      99             : 
     100    32240978 :         if (getResult < 0)
     101             :         {
     102             :             /* got a reset message */
     103         520 :             elog(DEBUG4, "cache state reset");
     104         520 :             SharedInvalidMessageCounter++;
     105         520 :             resetFunction();
     106         520 :             break;              /* nothing more to do */
     107             :         }
     108             : 
     109             :         /* Process them, being wary that a recursive call might eat some */
     110    32240458 :         nextmsg = 0;
     111    32240458 :         nummsgs = getResult;
     112             : 
     113    59459626 :         while (nextmsg < nummsgs)
     114             :         {
     115    27219172 :             SharedInvalidationMessage msg = messages[nextmsg++];
     116             : 
     117    27219172 :             SharedInvalidMessageCounter++;
     118    27219172 :             invalFunction(&msg);
     119             :         }
     120             : 
     121             :         /*
     122             :          * We only need to loop if the last SIGetDataEntries call (which might
     123             :          * have been within a recursive call) returned a full buffer.
     124             :          */
     125    32240454 :     } while (nummsgs == MAXINVALMSGS);
     126             : 
     127             :     /*
     128             :      * We are now caught up.  If we received a catchup signal, reset that
     129             :      * flag, and call SICleanupQueue().  This is not so much because we need
     130             :      * to flush dead messages right now, as that we want to pass on the
     131             :      * catchup signal to the next slowest backend.  "Daisy chaining" the
     132             :      * catchup signal this way avoids creating spikes in system load for what
     133             :      * should be just a background maintenance activity.
     134             :      */
     135    31514728 :     if (catchupInterruptPending)
     136             :     {
     137        5304 :         catchupInterruptPending = false;
     138        5304 :         elog(DEBUG4, "sinval catchup complete, cleaning queue");
     139        5304 :         SICleanupQueue(false, 0);
     140             :     }
     141    31514728 : }
     142             : 
     143             : 
     144             : /*
     145             :  * HandleCatchupInterrupt
     146             :  *
     147             :  * This is called when PROCSIG_CATCHUP_INTERRUPT is received.
     148             :  *
     149             :  * We used to directly call ProcessCatchupEvent directly when idle. These days
     150             :  * we just set a flag to do it later and notify the process of that fact by
     151             :  * setting the process's latch.
     152             :  */
     153             : void
     154        5306 : HandleCatchupInterrupt(void)
     155             : {
     156             :     /*
     157             :      * Note: this is called by a SIGNAL HANDLER. You must be very wary what
     158             :      * you do here.
     159             :      */
     160             : 
     161        5306 :     catchupInterruptPending = true;
     162             : 
     163             :     /* make sure the event is processed in due course */
     164        5306 :     SetLatch(MyLatch);
     165        5306 : }
     166             : 
     167             : /*
     168             :  * ProcessCatchupInterrupt
     169             :  *
     170             :  * The portion of catchup interrupt handling that runs outside of the signal
     171             :  * handler, which allows it to actually process pending invalidations.
     172             :  */
     173             : void
     174        6762 : ProcessCatchupInterrupt(void)
     175             : {
     176        9508 :     while (catchupInterruptPending)
     177             :     {
     178             :         /*
     179             :          * What we need to do here is cause ReceiveSharedInvalidMessages() to
     180             :          * run, which will do the necessary work and also reset the
     181             :          * catchupInterruptPending flag.  If we are inside a transaction we
     182             :          * can just call AcceptInvalidationMessages() to do this.  If we
     183             :          * aren't, we start and immediately end a transaction; the call to
     184             :          * AcceptInvalidationMessages() happens down inside transaction start.
     185             :          *
     186             :          * It is awfully tempting to just call AcceptInvalidationMessages()
     187             :          * without the rest of the xact start/stop overhead, and I think that
     188             :          * would actually work in the normal case; but I am not sure that
     189             :          * things would clean up nicely if we got an error partway through.
     190             :          */
     191        2746 :         if (IsTransactionOrTransactionBlock())
     192             :         {
     193          40 :             elog(DEBUG4, "ProcessCatchupEvent inside transaction");
     194          40 :             AcceptInvalidationMessages();
     195             :         }
     196             :         else
     197             :         {
     198        2706 :             elog(DEBUG4, "ProcessCatchupEvent outside transaction");
     199        2706 :             StartTransactionCommand();
     200        2706 :             CommitTransactionCommand();
     201             :         }
     202             :     }
     203        6762 : }