/*-------------------------------------------------------------------------
*
* freelist.c
- * routines for manipulating the buffer pool's replacement strategy.
+ * routines for manipulating the buffer pool's replacement strategy
+ * freelist.
*
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/storage/buffer/freelist.c,v 1.32 2003/11/13 00:40:01 wieck Exp $
+ * $Header: /cvsroot/pgsql/src/backend/storage/buffer/freelist.c,v 1.33 2003/11/13 05:34:58 wieck Exp $
*
*-------------------------------------------------------------------------
*/
#include "storage/bufmgr.h"
#include "storage/ipc.h"
#include "storage/proc.h"
-#include "access/xact.h"
-#define STRAT_LIST_UNUSED -1
-#define STRAT_LIST_B1 0
-#define STRAT_LIST_T1 1
-#define STRAT_LIST_T2 2
-#define STRAT_LIST_B2 3
-#define STRAT_NUM_LISTS 4
-
-#ifndef MAX
-#define MAX(a,b) (((a) > (b)) ? (a) : (b))
-#endif
-#ifndef MIN
-#define MIN(a,b) (((a) < (b)) ? (a) : (b))
-#endif
-
-/*
- * The Cache Directory Block (CDB) of the Adaptive Replacement Cache (ARC)
- */
-typedef struct bufstratcdb
-{
- int prev; /* links in the queue */
- int next;
- int list; /* current list */
- BufferTag buf_tag; /* buffer key */
- Buffer buf_id; /* currently assigned data buffer */
- TransactionId t1_xid; /* the xid this entry went onto T1 */
-} BufferStrategyCDB;
-
-/*
- * The shared ARC control information.
- */
-typedef struct bufstratcontrol
-{
-
- int target_T1_size; /* What T1 size are we aiming for */
- int listUnusedCDB; /* All unused StrategyCDB */
- int listHead[STRAT_NUM_LISTS]; /* ARC lists B1, T1, T2 and B2 */
- int listTail[STRAT_NUM_LISTS];
- int listSize[STRAT_NUM_LISTS];
- Buffer listFreeBuffers; /* List of unused buffers */
-
- long num_lookup; /* Some hit statistics */
- long num_hit[STRAT_NUM_LISTS];
- time_t stat_report;
-
- BufferStrategyCDB cdb[1]; /* The cache directory */
-} BufferStrategyControl;
-
-
-static BufferStrategyControl *StrategyControl = NULL;
-static BufferStrategyCDB *StrategyCDB = NULL;
-
-static int strategy_cdb_found;
-static int strategy_cdb_replace;
-static int strategy_get_from;
-
-int BufferStrategyStatInterval = 0;
-
-static bool strategy_hint_vacuum;
-static TransactionId strategy_vacuum_xid;
-
-
-#define T1_TARGET StrategyControl->target_T1_size
-#define B1_LENGTH StrategyControl->listSize[STRAT_LIST_B1]
-#define T1_LENGTH StrategyControl->listSize[STRAT_LIST_T1]
-#define T2_LENGTH StrategyControl->listSize[STRAT_LIST_T2]
-#define B2_LENGTH StrategyControl->listSize[STRAT_LIST_B2]
+static BufferDesc *SharedFreeList;
/*
- * Macro to remove a CDB from whichever list it currently is on
+ * State-checking macros
*/
-#define STRAT_LIST_REMOVE(cdb) \
-{ \
- AssertMacro((cdb)->list >= 0 && (cdb)->list < STRAT_NUM_LISTS); \
- if ((cdb)->prev < 0) \
- StrategyControl->listHead[(cdb)->list] = (cdb)->next; \
- else \
- StrategyCDB[(cdb)->prev].next = (cdb)->next; \
- if ((cdb)->next < 0) \
- StrategyControl->listTail[(cdb)->list] = (cdb)->prev; \
- else \
- StrategyCDB[(cdb)->next].prev = (cdb)->prev; \
- StrategyControl->listSize[(cdb)->list]--; \
- (cdb)->list = STRAT_LIST_UNUSED; \
-}
-/*
- * Macro to add a CDB to the tail of a list (MRU position)
- */
-#define STRAT_MRU_INSERT(cdb,l) \
-{ \
- AssertMacro((cdb)->list == STRAT_LIST_UNUSED); \
- if (StrategyControl->listTail[(l)] < 0) \
- { \
- (cdb)->prev = (cdb)->next = -1; \
- StrategyControl->listHead[(l)] = \
- StrategyControl->listTail[(l)] = \
- ((cdb) - StrategyCDB); \
- } \
- else \
- { \
- (cdb)->next = -1; \
- (cdb)->prev = StrategyControl->listTail[(l)]; \
- StrategyCDB[StrategyControl->listTail[(l)]].next = \
- ((cdb) - StrategyCDB); \
- StrategyControl->listTail[(l)] = \
- ((cdb) - StrategyCDB); \
- } \
- StrategyControl->listSize[(l)]++; \
- (cdb)->list = (l); \
-}
+#define IsInQueue(bf) \
+( \
+ AssertMacro((bf->freeNext != INVALID_DESCRIPTOR)), \
+ AssertMacro((bf->freePrev != INVALID_DESCRIPTOR)), \
+ AssertMacro((bf->flags & BM_FREE)) \
+)
-/*
- * Macro to add a CDB to the head of a list (LRU position)
- */
-#define STRAT_LRU_INSERT(cdb,l) \
-{ \
- AssertMacro((cdb)->list == STRAT_LIST_UNUSED); \
- if (StrategyControl->listHead[(l)] < 0) \
- { \
- (cdb)->prev = (cdb)->next = -1; \
- StrategyControl->listHead[(l)] = \
- StrategyControl->listTail[(l)] = \
- ((cdb) - StrategyCDB); \
- } \
- else \
- { \
- (cdb)->prev = -1; \
- (cdb)->next = StrategyControl->listHead[(l)]; \
- StrategyCDB[StrategyControl->listHead[(l)]].prev = \
- ((cdb) - StrategyCDB); \
- StrategyControl->listHead[(l)] = \
- ((cdb) - StrategyCDB); \
- } \
- StrategyControl->listSize[(l)]++; \
- (cdb)->list = (l); \
-}
+#define IsNotInQueue(bf) \
+( \
+ AssertMacro((bf->freeNext == INVALID_DESCRIPTOR)), \
+ AssertMacro((bf->freePrev == INVALID_DESCRIPTOR)), \
+ AssertMacro(! (bf->flags & BM_FREE)) \
+)
/*
- * StrategyBufferLookup
+ * AddBufferToFreelist
*
- * Lookup a page request in the cache directory. A buffer is only
- * returned for a T1 or T2 cache hit. B1 and B2 hits are only
- * remembered here to later affect the behaviour.
+ * In theory, this is the only routine that needs to be changed
+ * if the buffer replacement strategy changes. Just change
+ * the manner in which buffers are added to the freelist queue.
+ * Currently, they are added on an LRU basis.
*/
-BufferDesc *
-StrategyBufferLookup(BufferTag *tagPtr, bool recheck)
-{
- BufferStrategyCDB *cdb;
- time_t now;
-
- if (BufferStrategyStatInterval > 0)
- {
- time(&now);
- if (StrategyControl->stat_report + BufferStrategyStatInterval < now)
- {
- long all_hit, b1_hit, t1_hit, t2_hit, b2_hit;
- ErrorContextCallback *errcxtold;
-
- if (StrategyControl->num_lookup == 0)
- {
- all_hit = b1_hit = t1_hit = t2_hit = b2_hit = 0;
- }
- else
- {
- b1_hit = (StrategyControl->num_hit[STRAT_LIST_B1] * 100 /
- StrategyControl->num_lookup);
- t1_hit = (StrategyControl->num_hit[STRAT_LIST_T1] * 100 /
- StrategyControl->num_lookup);
- t2_hit = (StrategyControl->num_hit[STRAT_LIST_T2] * 100 /
- StrategyControl->num_lookup);
- b2_hit = (StrategyControl->num_hit[STRAT_LIST_B2] * 100 /
- StrategyControl->num_lookup);
- all_hit = b1_hit + t1_hit + t2_hit + b2_hit;
- }
-
- errcxtold = error_context_stack;
- error_context_stack = NULL;
- elog(DEBUG1, "ARC T1target=%5d B1len=%5d T1len=%5d T2len=%5d B2len=%5d",
- T1_TARGET, B1_LENGTH, T1_LENGTH, T2_LENGTH, B2_LENGTH);
- elog(DEBUG1, "ARC total =%4ld%% B1hit=%4ld%% T1hit=%4ld%% T2hit=%4ld%% B2hit=%4ld%%",
- all_hit, b1_hit, t1_hit, t2_hit, b2_hit);
- error_context_stack = errcxtold;
-
- StrategyControl->num_lookup = 0;
- StrategyControl->num_hit[STRAT_LIST_B1] = 0;
- StrategyControl->num_hit[STRAT_LIST_T1] = 0;
- StrategyControl->num_hit[STRAT_LIST_T2] = 0;
- StrategyControl->num_hit[STRAT_LIST_B2] = 0;
- StrategyControl->stat_report = now;
- }
- }
-
- /*
- * Count lookups
- */
- StrategyControl->num_lookup++;
-
- /*
- * Lookup the block in the shared hash table
- */
- strategy_cdb_found = BufTableLookup(tagPtr);
-
- /*
- * Handle CDB lookup miss
- */
- if (strategy_cdb_found < 0)
- {
- if (!recheck)
- {
- /*
- * This is an initial lookup and we have a complete
- * cache miss (block found nowhere). This means we
- * remember according to the current T1 size and the
- * target T1 size from where we take a block if we
- * need one later.
- */
- if (T1_LENGTH >= MAX(1, T1_TARGET))
- strategy_get_from = STRAT_LIST_T1;
- else
- strategy_get_from = STRAT_LIST_T2;
- }
-
- /* report cache miss */
- return NULL;
- }
-
- /*
- * We found a CDB
- */
- cdb = &StrategyCDB[strategy_cdb_found];
-
- /*
- * Count hits
- */
- StrategyControl->num_hit[cdb->list]++;
-
- /*
- * If this is a T2 hit, we simply move the CDB to the
- * T2 MRU position and return the found buffer.
- */
- if (cdb->list == STRAT_LIST_T2)
- {
- STRAT_LIST_REMOVE(cdb);
- STRAT_MRU_INSERT(cdb, STRAT_LIST_T2);
-
- return &BufferDescriptors[cdb->buf_id];
- }
-
- /*
- * If this is a T1 hit, we move the buffer to the T2 MRU
- * only if another transaction had read it into T1. This is
- * required because any UPDATE or DELETE in PostgreSQL does
- * multiple ReadBuffer(), first during the scan, later during
- * the heap_update() or heap_delete().
- */
- if (cdb->list == STRAT_LIST_T1)
- {
- if (!TransactionIdIsCurrentTransactionId(cdb->t1_xid))
- {
- STRAT_LIST_REMOVE(cdb);
- STRAT_MRU_INSERT(cdb, STRAT_LIST_T2);
- }
-
- return &BufferDescriptors[cdb->buf_id];
- }
-
- /*
- * In the case of a recheck we don't care about B1 or B2 hits here.
- * The bufmgr does this call only to make sure noone faulted in the
- * block while we where busy flushing another. Now for this really
- * to end up as a B1 or B2 cache hit, we must have been flushing for
- * quite some time as the block not only must have been read, but
- * also traveled through the queue and evicted from the T cache again
- * already.
- */
- if (recheck)
- return NULL;
-
- /*
- * Adjust the target size of the T1 cache depending on if this is
- * a B1 or B2 hit.
- */
- switch (cdb->list)
- {
- case STRAT_LIST_B1:
- /*
- * B1 hit means that the T1 cache is probably too
- * small. Adjust the T1 target size and continue
- * below.
- */
- T1_TARGET = MIN(T1_TARGET + MAX(B2_LENGTH / B1_LENGTH, 1),
- Data_Descriptors);
- break;
-
- case STRAT_LIST_B2:
- /*
- * B2 hit means that the T2 cache is probably too
- * small. Adjust the T1 target size and continue
- * below.
- */
- T1_TARGET = MAX(T1_TARGET - MAX(B1_LENGTH / B2_LENGTH, 1), 0);
- break;
-
- default:
- elog(ERROR, "Buffer hash table corrupted - CDB on list %d found",
- cdb->list);
- }
-
- /*
- * Decide where to take from if we will be out of
- * free blocks later in StrategyGetBuffer().
- */
- if (T1_LENGTH >= MAX(1, T1_TARGET))
- strategy_get_from = STRAT_LIST_T1;
- else
- strategy_get_from = STRAT_LIST_T2;
-
- /*
- * Even if we had seen the block in the past, it's data is
- * not currently in memory ... cache miss to the bufmgr.
- */
- return NULL;
-}
-
-
-/*
- * StrategyGetBuffer
- *
- * Called by the bufmgr to get the next candidate buffer to use in
- * BufferAlloc(). The only hard requirement BufferAlloc() has is that
- * this buffer must not currently be pinned.
- */
-BufferDesc *
-StrategyGetBuffer(void)
-{
- int cdb_id;
- BufferDesc *buf;
-
- if (StrategyControl->listFreeBuffers < 0)
- {
- /* We don't have a free buffer, must take one from T1 or T2 */
-
- if (strategy_get_from == STRAT_LIST_T1)
- {
- /*
- * We should take the first unpinned buffer from T1.
- */
- cdb_id = StrategyControl->listHead[STRAT_LIST_T1];
- while (cdb_id >= 0)
- {
- buf = &BufferDescriptors[StrategyCDB[cdb_id].buf_id];
- if (buf->refcount == 0)
- {
- strategy_cdb_replace = cdb_id;
- Assert(StrategyCDB[cdb_id].list == STRAT_LIST_T1);
- return buf;
- }
- cdb_id = StrategyCDB[cdb_id].next;
- }
-
- /*
- * No unpinned T1 buffer found - pardon T2 cache.
- */
- cdb_id = StrategyControl->listHead[STRAT_LIST_T2];
- while (cdb_id >= 0)
- {
- buf = &BufferDescriptors[StrategyCDB[cdb_id].buf_id];
- if (buf->refcount == 0)
- {
- strategy_cdb_replace = cdb_id;
- Assert(StrategyCDB[cdb_id].list == STRAT_LIST_T2);
- return buf;
- }
- cdb_id = StrategyCDB[cdb_id].next;
- }
-
- /*
- * No unpinned buffers at all!!!
- */
- elog(ERROR, "StrategyGetBuffer(): Out of unpinned buffers");
- }
- else
- {
- /*
- * We should take the first unpinned buffer from T2.
- */
- cdb_id = StrategyControl->listHead[STRAT_LIST_T2];
- while (cdb_id >= 0)
- {
- buf = &BufferDescriptors[StrategyCDB[cdb_id].buf_id];
- if (buf->refcount == 0)
- {
- strategy_cdb_replace = cdb_id;
- Assert(StrategyCDB[cdb_id].list == STRAT_LIST_T2);
- return buf;
- }
- cdb_id = StrategyCDB[cdb_id].next;
- }
-
- /*
- * No unpinned T2 buffer found - pardon T1 cache.
- */
- cdb_id = StrategyControl->listHead[STRAT_LIST_T1];
- while (cdb_id >= 0)
- {
- buf = &BufferDescriptors[StrategyCDB[cdb_id].buf_id];
- if (buf->refcount == 0)
- {
- strategy_cdb_replace = cdb_id;
- Assert(StrategyCDB[cdb_id].list == STRAT_LIST_T1);
- return buf;
- }
- cdb_id = StrategyCDB[cdb_id].next;
- }
-
- /*
- * No unpinned buffers at all!!!
- */
- elog(ERROR, "StrategyGetBuffer(): Out of unpinned buffers");
- }
- }
- else
- {
- /* There is a completely free buffer available - take it */
-
- /*
- * Note: This code uses the side effect that a free buffer
- * can never be pinned or dirty and therefore the call to
- * StrategyReplaceBuffer() will happen without the bufmgr
- * releasing the bufmgr-lock in the meantime. That means,
- * that there will never be any reason to recheck. Otherwise
- * we would leak shared buffers here!
- */
- strategy_cdb_replace = -1;
- buf = &BufferDescriptors[StrategyControl->listFreeBuffers];
-
- StrategyControl->listFreeBuffers = buf->bufNext;
- buf->bufNext = -1;
-
- /* Buffer of freelist cannot be pinned */
- Assert(buf->refcount == 0);
-
- return buf;
- }
-
- /* not reached */
- return NULL;
-}
-
-
-/*
- * StrategyReplaceBuffer
- *
- * Called by the buffer manager to inform us that he possibly flushed
- * a buffer and is now about to replace the content. Prior to this call,
- * the cache algorithm still reports the buffer as in the cache. After
- * this call we report the new block, even if IO might still need to
- * start.
- */
-void
-StrategyReplaceBuffer(BufferDesc *buf, Relation rnode, BlockNumber blockNum)
-{
- BufferStrategyCDB *cdb_found;
- BufferStrategyCDB *cdb_replace;
-
- if (strategy_cdb_found >= 0)
- {
- /* This was a ghost buffer cache hit (B1 or B2) */
- cdb_found = &StrategyCDB[strategy_cdb_found];
-
- /* Assert that the buffer remembered in cdb_found is the one */
- /* the buffer manager is currently faulting in */
- Assert(BUFFERTAG_EQUALS(&(cdb_found->buf_tag), rnode, blockNum));
-
- if (strategy_cdb_replace >= 0)
- {
- /* We are satisfying it with an evicted T buffer */
- cdb_replace = &StrategyCDB[strategy_cdb_replace];
-
- /* Assert that the buffer remembered in cdb_replace is */
- /* the one the buffer manager has just evicted */
- Assert(cdb_replace->list == STRAT_LIST_T1 ||
- cdb_replace->list == STRAT_LIST_T2);
- Assert(cdb_replace->buf_id == buf->buf_id);
- Assert(BUFFERTAGS_EQUAL(&(cdb_replace->buf_tag), &(buf->tag)));
-
- /* If this was a T1 buffer faulted in by vacuum, just */
- /* do not cause the CDB end up in the B1 list, so that */
- /* the vacuum scan does not affect T1_target adjusting */
- if (strategy_hint_vacuum)
- {
- BufTableDelete(&(cdb_replace->buf_tag));
- STRAT_LIST_REMOVE(cdb_replace);
- cdb_replace->buf_id = -1;
- cdb_replace->next = StrategyControl->listUnusedCDB;
- StrategyControl->listUnusedCDB = strategy_cdb_replace;
- }
- else
- {
- /* Under normal circumstances move the evicted */
- /* T list entry to it's corresponding B list */
- if (cdb_replace->list == STRAT_LIST_T1)
- {
- STRAT_LIST_REMOVE(cdb_replace);
- STRAT_MRU_INSERT(cdb_replace, STRAT_LIST_B1);
- }
- else
- {
- STRAT_LIST_REMOVE(cdb_replace);
- STRAT_MRU_INSERT(cdb_replace, STRAT_LIST_B2);
- }
- }
- /* And clear it's block reference */
- cdb_replace->buf_id = -1;
- }
- else
- {
- /* or we satisfy it with an unused buffer */
- }
-
- /* Now the found B CDB get's the buffer and is moved to T2 */
- cdb_found->buf_id = buf->buf_id;
- STRAT_LIST_REMOVE(cdb_found);
- STRAT_MRU_INSERT(cdb_found, STRAT_LIST_T2);
- }
- else
- {
- /* This was a complete cache miss, so we need to create */
- /* a new CDB. The goal is to keep T1len+B1len <= c */
-
- if (B1_LENGTH > 0 && (T1_LENGTH + B1_LENGTH) >= Data_Descriptors)
- {
- /* So if B1 isn't empty and T1len+B1len >= c we take B1-LRU */
- cdb_found = &StrategyCDB[StrategyControl->listHead[STRAT_LIST_B1]];
-
- BufTableDelete(&(cdb_found->buf_tag));
- STRAT_LIST_REMOVE(cdb_found);
- }
- else
- {
- /* Otherwise, we try to use a free one */
- if (StrategyControl->listUnusedCDB >= 0)
- {
- cdb_found = &StrategyCDB[StrategyControl->listUnusedCDB];
- StrategyControl->listUnusedCDB = cdb_found->next;
- }
- else
- {
- /* If there isn't, we take B2-LRU ... except if */
- /* T1len+B1len+T2len = c ... oh my */
- if (B2_LENGTH > 0)
- cdb_found = &StrategyCDB[StrategyControl->listHead[STRAT_LIST_B2]];
- else
- cdb_found = &StrategyCDB[StrategyControl->listHead[STRAT_LIST_B1]];
-
- BufTableDelete(&(cdb_found->buf_tag));
- STRAT_LIST_REMOVE(cdb_found);
- }
- }
-
- /* Set the CDB's buf_tag and insert the hash key */
- INIT_BUFFERTAG(&(cdb_found->buf_tag), rnode, blockNum);
- BufTableInsert(&(cdb_found->buf_tag), (cdb_found - StrategyCDB));
-
- if (strategy_cdb_replace >= 0)
- {
- /* The buffer was formerly in a T list, move it's CDB
- * to the corresponding B list */
- cdb_replace = &StrategyCDB[strategy_cdb_replace];
-
- Assert(cdb_replace->list == STRAT_LIST_T1 ||
- cdb_replace->list == STRAT_LIST_T2);
- Assert(cdb_replace->buf_id == buf->buf_id);
- Assert(BUFFERTAGS_EQUAL(&(cdb_replace->buf_tag), &(buf->tag)));
-
- if (cdb_replace->list == STRAT_LIST_T1)
- {
- STRAT_LIST_REMOVE(cdb_replace);
- STRAT_MRU_INSERT(cdb_replace, STRAT_LIST_B1);
- }
- else
- {
- STRAT_LIST_REMOVE(cdb_replace);
- STRAT_MRU_INSERT(cdb_replace, STRAT_LIST_B2);
- }
- /* And clear it's block reference */
- cdb_replace->buf_id = -1;
- }
- else
- {
- /* or we satisfy it with an unused buffer */
- }
-
- /* Assign the buffer id to the new CDB */
- cdb_found->buf_id = buf->buf_id;
-
- /*
- * Specialized VACUUM optimization. If this "complete cache miss"
- * happened because vacuum needed the page, we want it later on
- * to be placed at the LRU instead of the MRU position of T1.
- */
- if (strategy_hint_vacuum)
- {
- if (strategy_vacuum_xid != GetCurrentTransactionId())
- {
- strategy_hint_vacuum = false;
- STRAT_MRU_INSERT(cdb_found, STRAT_LIST_T1);
- }
- else
- STRAT_LRU_INSERT(cdb_found, STRAT_LIST_T1);
-
- }
- else
- STRAT_MRU_INSERT(cdb_found, STRAT_LIST_T1);
-
- /*
- * Remember the Xid when this buffer went onto T1 to avoid
- * a single UPDATE promoting a newcomer straight into T2.
- */
- cdb_found->t1_xid = GetCurrentTransactionId();
- }
-}
-
-
-/*
- * StrategyInvalidateBuffer
- *
- * Called by the buffer manager to inform us that a buffer content
- * is no longer valid. We simply throw away any eventual existing
- * buffer hash entry and move the CDB and buffer to the free lists.
- */
-void
-StrategyInvalidateBuffer(BufferDesc *buf)
-{
- int cdb_id;
- BufferStrategyCDB *cdb;
-
- cdb_id = BufTableLookup(&(buf->tag));
-
- /* If we have the buffer somewhere in the directory, remove it
- * and add the CDB to the list of unused CDB's. */
- if (cdb_id >= 0)
- {
- cdb = &StrategyCDB[cdb_id];
- BufTableDelete(&(cdb->buf_tag));
- STRAT_LIST_REMOVE(cdb);
- cdb->buf_id = -1;
- cdb->next = StrategyControl->listUnusedCDB;
- StrategyControl->listUnusedCDB = cdb_id;
- }
-
- /* Buffer is unreferenced now and should not contain any valid data
- * so add it to the list of free buffers */
- buf->bufNext = StrategyControl->listFreeBuffers;
- StrategyControl->listFreeBuffers = buf->buf_id;
-}
-
-
-void
-StrategyHintVacuum(bool vacuum_active)
-{
- strategy_hint_vacuum = vacuum_active;
- strategy_vacuum_xid = GetCurrentTransactionId();
-}
-
-
-int
-StrategyDirtyBufferList(int *buffer_list, int max_buffers)
-{
- int num_buffer_dirty = 0;
- int cdb_id_t1;
- int cdb_id_t2;
- int buf_id;
- BufferDesc *buf;
-
- /*
- * Traverse the T1 and T2 list LRU to MRU in "parallel"
- * and add all dirty buffers found in that order to the list.
- * The ARC strategy keeps all used buffers including pinned ones
- * in the T1 or T2 list. So we cannot loose any dirty buffers.
- */
- cdb_id_t1 = StrategyControl->listHead[STRAT_LIST_T1];
- cdb_id_t2 = StrategyControl->listHead[STRAT_LIST_T2];
-
- while ((cdb_id_t1 >= 0 || cdb_id_t2 >= 0) &&
- num_buffer_dirty < max_buffers)
- {
- if (cdb_id_t1 >= 0)
- {
- buf_id = StrategyCDB[cdb_id_t1].buf_id;
- buf = &BufferDescriptors[buf_id];
-
- if (buf->flags & BM_VALID)
- {
- if ((buf->flags & BM_DIRTY) || (buf->cntxDirty))
- {
- buffer_list[num_buffer_dirty++] = buf_id;
- }
- }
-
- cdb_id_t1 = StrategyCDB[cdb_id_t1].next;
- }
-
- if (cdb_id_t2 >= 0)
- {
- buf_id = StrategyCDB[cdb_id_t2].buf_id;
- buf = &BufferDescriptors[buf_id];
-
- if (buf->flags & BM_VALID)
- {
- if ((buf->flags & BM_DIRTY) || (buf->cntxDirty))
- {
- buffer_list[num_buffer_dirty++] = buf_id;
- }
- }
-
- cdb_id_t2 = StrategyCDB[cdb_id_t2].next;
- }
- }
-
- return num_buffer_dirty;
-}
-
-
-/*
- * StrategyInitialize -- initialize the buffer cache replacement
- * strategy.
- *
- * Assume: All of the buffers are already building a linked list.
- * Only called by postmaster and only during initialization.
- */
-void
-StrategyInitialize(bool init)
+static void
+AddBufferToFreelist(BufferDesc *bf)
{
- bool found;
- int i;
-
- /*
- * Initialize the shared CDB lookup hashtable
- */
- InitBufTable(Data_Descriptors * 2);
-
- /*
- * Get or create the shared strategy control block and the CDB's
- */
- StrategyControl = (BufferStrategyControl *)
- ShmemInitStruct("Buffer Strategy Status",
- sizeof(BufferStrategyControl) +
- sizeof(BufferStrategyCDB) * (Data_Descriptors * 2 - 1),
- &found);
- StrategyCDB = &(StrategyControl->cdb[0]);
-
- if (!found)
- {
- /*
- * Only done once, usually in postmaster
- */
- Assert(init);
-
- /*
- * Grab the whole linked list of free buffers for our
- * strategy
- */
- StrategyControl->listFreeBuffers = 0;
-
- /*
- * We start off with a target T1 list size of
- * half the available cache blocks.
- */
- StrategyControl->target_T1_size = Data_Descriptors / 2;
-
- /*
- * Initialize B1, T1, T2 and B2 lists to be empty
- */
- for (i = 0; i < STRAT_NUM_LISTS; i++)
- {
- StrategyControl->listHead[i] = -1;
- StrategyControl->listTail[i] = -1;
- StrategyControl->listSize[i] = 0;
- StrategyControl->num_hit[i] = 0;
- }
- StrategyControl->num_lookup = 0;
- StrategyControl->stat_report = 0;
-
- /*
- * All CDB's are linked as the listUnusedCDB
- */
- for (i = 0; i < Data_Descriptors * 2; i++)
- {
- StrategyCDB[i].next = i + 1;
- StrategyCDB[i].list = STRAT_LIST_UNUSED;
- CLEAR_BUFFERTAG(&(StrategyCDB[i].buf_tag));
- StrategyCDB[i].buf_id = -1;
- }
- StrategyCDB[Data_Descriptors * 2 - 1].next = -1;
- StrategyControl->listUnusedCDB = 0;
- }
- else
- {
- Assert(!init);
- }
+#ifdef BMTRACE
+ _bm_trace(bf->tag.relId.dbId, bf->tag.relId.relId, bf->tag.blockNum,
+ BufferDescriptorGetBuffer(bf), BMT_DEALLOC);
+#endif /* BMTRACE */
+ IsNotInQueue(bf);
+
+ /* change bf so it points to inFrontOfNew and its successor */
+ bf->freePrev = SharedFreeList->freePrev;
+ bf->freeNext = Free_List_Descriptor;
+
+ /* insert new into chain */
+ BufferDescriptors[bf->freeNext].freePrev = bf->buf_id;
+ BufferDescriptors[bf->freePrev].freeNext = bf->buf_id;
}
-
#undef PinBuffer
/*
if (buf->refcount == 0)
{
+ IsInQueue(buf);
+
+ /* remove from freelist queue */
+ BufferDescriptors[buf->freeNext].freePrev = buf->freePrev;
+ BufferDescriptors[buf->freePrev].freeNext = buf->freeNext;
+ buf->freeNext = buf->freePrev = INVALID_DESCRIPTOR;
+
/* mark buffer as no longer free */
buf->flags &= ~BM_FREE;
}
+ else
+ IsNotInQueue(buf);
if (PrivateRefCount[b] == 0)
buf->refcount++;
{
int b = BufferDescriptorGetBuffer(buf) - 1;
+ IsNotInQueue(buf);
Assert(buf->refcount > 0);
Assert(PrivateRefCount[b] > 0);
PrivateRefCount[b]--;
if (buf->refcount == 0)
{
/* buffer is now unpinned */
+ AddBufferToFreelist(buf);
buf->flags |= BM_FREE;
}
else if ((buf->flags & BM_PIN_COUNT_WAITER) != 0 &&
}
#endif
+/*
+ * GetFreeBuffer() -- get the 'next' buffer from the freelist.
+ */
+BufferDesc *
+GetFreeBuffer(void)
+{
+ BufferDesc *buf;
+
+ if (Free_List_Descriptor == SharedFreeList->freeNext)
+ {
+ /* queue is empty. All buffers in the buffer pool are pinned. */
+ ereport(ERROR,
+ (errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ errmsg("out of free buffers")));
+ return NULL;
+ }
+ buf = &(BufferDescriptors[SharedFreeList->freeNext]);
+
+ /* remove from freelist queue */
+ BufferDescriptors[buf->freeNext].freePrev = buf->freePrev;
+ BufferDescriptors[buf->freePrev].freeNext = buf->freeNext;
+ buf->freeNext = buf->freePrev = INVALID_DESCRIPTOR;
+
+ buf->flags &= ~(BM_FREE);
+
+ return buf;
+}
+
+/*
+ * InitFreeList -- initialize the dummy buffer descriptor used
+ * as a freelist head.
+ *
+ * Assume: All of the buffers are already linked in a circular
+ * queue. Only called by postmaster and only during
+ * initialization.
+ */
+void
+InitFreeList(bool init)
+{
+ SharedFreeList = &(BufferDescriptors[Free_List_Descriptor]);
+
+ if (init)
+ {
+ /* we only do this once, normally in the postmaster */
+ SharedFreeList->data = INVALID_OFFSET;
+ SharedFreeList->flags = 0;
+ SharedFreeList->flags &= ~(BM_VALID | BM_DELETED | BM_FREE);
+ SharedFreeList->buf_id = Free_List_Descriptor;
+
+ /* insert it into a random spot in the circular queue */
+ SharedFreeList->freeNext = BufferDescriptors[0].freeNext;
+ SharedFreeList->freePrev = 0;
+ BufferDescriptors[SharedFreeList->freeNext].freePrev =
+ BufferDescriptors[SharedFreeList->freePrev].freeNext =
+ Free_List_Descriptor;
+ }
+}
+
/*
* print out the free list and check for breaks.
projects / postgresql / commitdiff