postgres/src/backend/storage/buffer/buf_init.c

/*-------------------------------------------------------------------------
 *
 * buf_init.c--
 *    buffer manager initialization routines
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    $Header: /cvsroot/pgsql/src/backend/storage/buffer/buf_init.c,v 1.10 1997/07/28 00:54:33 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#include <sys/types.h>
#include <sys/file.h>
#include <stdio.h>
#include <math.h>
#include <signal.h>

#include "postgres.h"

/* declarations split between these three files */
#include "storage/buf.h"
#include "storage/buf_internals.h"
#include "storage/bufmgr.h"

#include "storage/fd.h"
#include "storage/ipc.h"
#include "storage/shmem.h"
#include "storage/spin.h"
#include "storage/smgr.h"
#include "storage/lmgr.h"
#include "miscadmin.h"
#include "utils/builtins.h"
#include "utils/dynahash.h"
#include "utils/hsearch.h"
#include "utils/memutils.h"
#include "executor/execdebug.h"	/* for NDirectFileRead */
#include "catalog/catalog.h"

/*
 *  if BMTRACE is defined, we trace the last 200 buffer allocations and
 *  deallocations in a circular buffer in shared memory.
 */
#ifdef	BMTRACE
bmtrace	*TraceBuf;
long	*CurTraceBuf;
#define	BMT_LIMIT	200
#endif /* BMTRACE */
int ShowPinTrace = 0;

int		NBuffers = NDBUFS;  /* NDBUFS defined in miscadmin.h */
int		Data_Descriptors;
int		Free_List_Descriptor;
int		Lookup_List_Descriptor;
int		Num_Descriptors;

BufferDesc 	*BufferDescriptors;
BufferBlock 	BufferBlocks;
#ifndef HAS_TEST_AND_SET
long	*NWaitIOBackendP;
#endif

extern IpcSemaphoreId      WaitIOSemId;

long	*PrivateRefCount;	/* also used in freelist.c */
long	*LastRefCount;  /* refcounts of last ExecMain level */
long    *CommitInfoNeedsSave;  /* to write buffers where we have filled in */
                               /* t_tmin (or t_tmax)                       */

/*
 * Data Structures:
 *      buffers live in a freelist and a lookup data structure.
 *	
 *
 * Buffer Lookup:
 *	Two important notes.  First, the buffer has to be
 *	available for lookup BEFORE an IO begins.  Otherwise
 *	a second process trying to read the buffer will 
 *	allocate its own copy and the buffeer pool will 
 *	become inconsistent.
 *
 * Buffer Replacement:
 *	see freelist.c.  A buffer cannot be replaced while in
 *	use either by data manager or during IO.
 *
 * WriteBufferBack:
 *	currently, a buffer is only written back at the time
 *	it is selected for replacement.  It should 
 *	be done sooner if possible to reduce latency of 
 *	BufferAlloc().  Maybe there should be a daemon process.
 *
 * Synchronization/Locking:
 *
 * BufMgrLock lock -- must be acquired before manipulating the 
 * 	buffer queues (lookup/freelist).  Must be released 
 * 	before exit and before doing any IO.  
 *
 * IO_IN_PROGRESS -- this is a flag in the buffer descriptor.
 *      It must be set when an IO is initiated and cleared at
 *      the end of  the IO.  It is there to make sure that one
 *	process doesn't start to use a buffer while another is
 *	faulting it in.  see IOWait/IOSignal.
 *
 * refcount --  A buffer is pinned during IO and immediately
 *	after a BufferAlloc().  A buffer is always either pinned
 *	or on the freelist but never both.  The buffer must be
 *	released, written, or flushed before the end of 
 * 	transaction.
 *
 * PrivateRefCount -- Each buffer also has a private refcount the keeps
 *	track of the number of times the buffer is pinned in the current
 *	processes.  This is used for two purposes, first, if we pin a
 *	a buffer more than once, we only need to change the shared refcount
 *	once, thus only lock the buffer pool once, second, when a transaction
 *	aborts, it should only unpin the buffers exactly the number of times it
 *	has pinned them, so that it will not blow away buffers of another
 *	backend.
 *
 */

SPINLOCK BufMgrLock;

long int ReadBufferCount;
long int ReadLocalBufferCount;
long int BufferHitCount;
long int LocalBufferHitCount;
long int BufferFlushCount;
long int LocalBufferFlushCount;


/*
 * Initialize module:
 *
 * should calculate size of pool dynamically based on the
 * amount of available memory.
 */
void
InitBufferPool(IPCKey key)
{
    bool foundBufs,foundDescs;
    int i;
    
    /* check padding of BufferDesc and BufferHdr */
    /* we need both checks because a sbufdesc_padded > PADDED_SBUFDESC_SIZE
       will shrink sbufdesc to the required size, which is bad */
    if (sizeof(struct sbufdesc) != PADDED_SBUFDESC_SIZE ||
	sizeof(struct sbufdesc_unpadded) > PADDED_SBUFDESC_SIZE)
    	elog(WARN,"Internal error:  sbufdesc does not have the proper size, "
				"contact the Postgres developers");
    if (sizeof(struct sbufdesc_unpadded) <= PADDED_SBUFDESC_SIZE/2)
    	elog(WARN,"Internal error:  sbufdesc is greatly over-sized, "
				"contact the Postgres developers");

    Data_Descriptors = NBuffers;
    Free_List_Descriptor = Data_Descriptors;
    Lookup_List_Descriptor = Data_Descriptors + 1;
    Num_Descriptors = Data_Descriptors + 1;
    
    SpinAcquire(BufMgrLock);
    
#ifdef BMTRACE
    CurTraceBuf = (long *) ShmemInitStruct("Buffer trace",
					   (BMT_LIMIT * sizeof(bmtrace)) + sizeof(long),
					   &foundDescs);
    if (!foundDescs)
	memset(CurTraceBuf, 0, (BMT_LIMIT * sizeof(bmtrace)) + sizeof(long));
    
    TraceBuf = (bmtrace *) &(CurTraceBuf[1]);
#endif
    
    BufferDescriptors = (BufferDesc *)
	ShmemInitStruct("Buffer Descriptors",
			Num_Descriptors*sizeof(BufferDesc),&foundDescs);
    
    BufferBlocks = (BufferBlock)
	ShmemInitStruct("Buffer Blocks",
			NBuffers*BLCKSZ,&foundBufs);
    
#ifndef HAS_TEST_AND_SET
    {
	bool foundNWaitIO;
	
	NWaitIOBackendP = (long *)ShmemInitStruct("#Backends Waiting IO",
						  sizeof(long),
						  &foundNWaitIO);
	if (!foundNWaitIO)
	    *NWaitIOBackendP = 0;
    }
#endif
    
    if (foundDescs || foundBufs) {
	
	/* both should be present or neither */
	Assert(foundDescs && foundBufs);
	
    } else {
	BufferDesc *buf;
	unsigned long block;
	
	buf = BufferDescriptors;
	block = (unsigned long) BufferBlocks;
	
	/*
	 * link the buffers into a circular, doubly-linked list to
	 * initialize free list.  Still don't know anything about
	 * replacement strategy in this file.
	 */
	for (i = 0; i < Data_Descriptors; block+=BLCKSZ,buf++,i++) {
	    Assert(ShmemIsValid((unsigned long)block));
	    
	    buf->freeNext = i+1;
	    buf->freePrev = i-1;
	    
	    CLEAR_BUFFERTAG(&(buf->tag));
	    buf->data = MAKE_OFFSET(block);
	    buf->flags = (BM_DELETED | BM_FREE | BM_VALID);
	    buf->refcount = 0;
	    buf->buf_id = i;
#ifdef HAS_TEST_AND_SET
	    S_INIT_LOCK(&(buf->io_in_progress_lock));
#endif
	}
	
	/* close the circular queue */
	BufferDescriptors[0].freePrev = Data_Descriptors-1;
	BufferDescriptors[Data_Descriptors-1].freeNext = 0;
    }
    
    /* Init the rest of the module */
    InitBufTable();
    InitFreeList(!foundDescs);
    
    SpinRelease(BufMgrLock);
    
#ifndef HAS_TEST_AND_SET
    {
	int status;
	WaitIOSemId = IpcSemaphoreCreate(IPCKeyGetWaitIOSemaphoreKey(key),
					 1, IPCProtection, 0, 1, &status);
    }
#endif
    PrivateRefCount = (long *) calloc(NBuffers, sizeof(long));
    LastRefCount = (long *) calloc(NBuffers, sizeof(long));
    CommitInfoNeedsSave = (long *) calloc(NBuffers, sizeof(long));
}

/* -----------------------------------------------------
 * BufferShmemSize
 *
 * compute the size of shared memory for the buffer pool including
 * data pages, buffer descriptors, hash tables, etc.
 * ----------------------------------------------------
 */
int
BufferShmemSize()
{
    int size = 0;
    int nbuckets;
    int nsegs;
    int tmp;
    
    nbuckets = 1 << (int)my_log2((NBuffers - 1) / DEF_FFACTOR + 1);
    nsegs = 1 << (int)my_log2((nbuckets - 1) / DEF_SEGSIZE + 1);
    
    /* size of shmem binding table */
    size += MAXALIGN(my_log2(BTABLE_SIZE) * sizeof(void *)); /* HTAB->dir */
    size += MAXALIGN(sizeof(HHDR));			     /* HTAB->hctl */
    size += MAXALIGN(DEF_SEGSIZE * sizeof(SEGMENT));
    size += BUCKET_ALLOC_INCR * 
	(MAXALIGN(sizeof(BUCKET_INDEX)) +
	 MAXALIGN(BTABLE_KEYSIZE) +
	 MAXALIGN(BTABLE_DATASIZE));
    
    /* size of buffer descriptors */
    size += MAXALIGN((NBuffers + 1) * sizeof(BufferDesc));
    
    /* size of data pages */
    size += NBuffers * MAXALIGN(BLCKSZ);
    
    /* size of buffer hash table */
    size += MAXALIGN(my_log2(NBuffers) * sizeof(void *)); /* HTAB->dir */
    size += MAXALIGN(sizeof(HHDR));			  /* HTAB->hctl */
    size += nsegs * MAXALIGN(DEF_SEGSIZE * sizeof(SEGMENT));
    tmp = (int)ceil((double)NBuffers/BUCKET_ALLOC_INCR);
    size += tmp * BUCKET_ALLOC_INCR * 
	(MAXALIGN(sizeof(BUCKET_INDEX)) +
	 MAXALIGN(sizeof(BufferTag)) +
	 MAXALIGN(sizeof(Buffer)));
    
#ifdef BMTRACE
    size += (BMT_LIMIT * sizeof(bmtrace)) + sizeof(long);
#endif
    return size;
}