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Diffstat (limited to 'src/backend/storage/buffer/bufmgr.c')
-rw-r--r--src/backend/storage/buffer/bufmgr.c508
1 files changed, 334 insertions, 174 deletions
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index c664984d0a1..29f10e59568 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -436,11 +436,12 @@ static bool PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy);
static void PinBuffer_Locked(BufferDesc *buf);
static void UnpinBuffer(BufferDesc *buf, bool fixOwner);
static void BufferSync(int flags);
+static uint32 WaitBufHdrUnlocked(BufferDesc *buf);
static int SyncOneBuffer(int buf_id, bool skip_recently_used, WritebackContext *flush_context);
static void WaitIO(BufferDesc *buf);
static bool StartBufferIO(BufferDesc *buf, bool forInput);
static void TerminateBufferIO(BufferDesc *buf, bool clear_dirty,
- int set_flag_bits);
+ uint32 set_flag_bits);
static void shared_buffer_write_error_callback(void *arg);
static void local_buffer_write_error_callback(void *arg);
static BufferDesc *BufferAlloc(SMgrRelation smgr,
@@ -816,8 +817,11 @@ ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
if (isLocalBuf)
{
/* Only need to adjust flags */
- Assert(bufHdr->flags & BM_VALID);
- bufHdr->flags &= ~BM_VALID;
+ uint32 buf_state = pg_atomic_read_u32(&bufHdr->state);
+
+ Assert(buf_state & BM_VALID);
+ buf_state &= ~BM_VALID;
+ pg_atomic_write_u32(&bufHdr->state, buf_state);
}
else
{
@@ -828,10 +832,11 @@ ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
*/
do
{
- LockBufHdr(bufHdr);
- Assert(bufHdr->flags & BM_VALID);
- bufHdr->flags &= ~BM_VALID;
- UnlockBufHdr(bufHdr);
+ uint32 buf_state = LockBufHdr(bufHdr);
+
+ Assert(buf_state & BM_VALID);
+ buf_state &= ~BM_VALID;
+ UnlockBufHdr(bufHdr, buf_state);
} while (!StartBufferIO(bufHdr, true));
}
}
@@ -848,7 +853,7 @@ ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
* it's not been recycled) but come right back here to try smgrextend
* again.
*/
- Assert(!(bufHdr->flags & BM_VALID)); /* spinlock not needed */
+ Assert(!(pg_atomic_read_u32(&bufHdr->state) & BM_VALID)); /* spinlock not needed */
bufBlock = isLocalBuf ? LocalBufHdrGetBlock(bufHdr) : BufHdrGetBlock(bufHdr);
@@ -933,7 +938,10 @@ ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
if (isLocalBuf)
{
/* Only need to adjust flags */
- bufHdr->flags |= BM_VALID;
+ uint32 buf_state = pg_atomic_read_u32(&bufHdr->state);
+
+ buf_state |= BM_VALID;
+ pg_atomic_write_u32(&bufHdr->state, buf_state);
}
else
{
@@ -987,10 +995,11 @@ BufferAlloc(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
BufferTag oldTag; /* previous identity of selected buffer */
uint32 oldHash; /* hash value for oldTag */
LWLock *oldPartitionLock; /* buffer partition lock for it */
- BufFlags oldFlags;
+ uint32 oldFlags;
int buf_id;
BufferDesc *buf;
bool valid;
+ uint32 buf_state;
/* create a tag so we can lookup the buffer */
INIT_BUFFERTAG(newTag, smgr->smgr_rnode.node, forkNum, blockNum);
@@ -1059,12 +1068,12 @@ BufferAlloc(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
* Select a victim buffer. The buffer is returned with its header
* spinlock still held!
*/
- buf = StrategyGetBuffer(strategy);
+ buf = StrategyGetBuffer(strategy, &buf_state);
- Assert(buf->refcount == 0);
+ Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 0);
/* Must copy buffer flags while we still hold the spinlock */
- oldFlags = buf->flags;
+ oldFlags = buf_state & BUF_FLAG_MASK;
/* Pin the buffer and then release the buffer spinlock */
PinBuffer_Locked(buf);
@@ -1108,9 +1117,9 @@ BufferAlloc(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
XLogRecPtr lsn;
/* Read the LSN while holding buffer header lock */
- LockBufHdr(buf);
+ buf_state = LockBufHdr(buf);
lsn = BufferGetLSN(buf);
- UnlockBufHdr(buf);
+ UnlockBufHdr(buf, buf_state);
if (XLogNeedsFlush(lsn) &&
StrategyRejectBuffer(strategy, buf))
@@ -1254,7 +1263,7 @@ BufferAlloc(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
/*
* Need to lock the buffer header too in order to change its tag.
*/
- LockBufHdr(buf);
+ buf_state = LockBufHdr(buf);
/*
* Somebody could have pinned or re-dirtied the buffer while we were
@@ -1262,11 +1271,11 @@ BufferAlloc(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
* recycle this buffer; we must undo everything we've done and start
* over with a new victim buffer.
*/
- oldFlags = buf->flags;
- if (buf->refcount == 1 && !(oldFlags & BM_DIRTY))
+ oldFlags = buf_state & BUF_FLAG_MASK;
+ if (BUF_STATE_GET_REFCOUNT(buf_state) == 1 && !(oldFlags & BM_DIRTY))
break;
- UnlockBufHdr(buf);
+ UnlockBufHdr(buf, buf_state);
BufTableDelete(&newTag, newHash);
if ((oldFlags & BM_TAG_VALID) &&
oldPartitionLock != newPartitionLock)
@@ -1284,14 +1293,15 @@ BufferAlloc(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
* 1 so that the buffer can survive one clock-sweep pass.)
*/
buf->tag = newTag;
- buf->flags &= ~(BM_VALID | BM_DIRTY | BM_JUST_DIRTIED | BM_CHECKPOINT_NEEDED | BM_IO_ERROR | BM_PERMANENT);
+ buf_state &= ~(BM_VALID | BM_DIRTY | BM_JUST_DIRTIED |
+ BM_CHECKPOINT_NEEDED | BM_IO_ERROR | BM_PERMANENT |
+ BUF_USAGECOUNT_MASK);
if (relpersistence == RELPERSISTENCE_PERMANENT)
- buf->flags |= BM_TAG_VALID | BM_PERMANENT;
+ buf_state |= BM_TAG_VALID | BM_PERMANENT | BUF_USAGECOUNT_ONE;
else
- buf->flags |= BM_TAG_VALID;
- buf->usage_count = 1;
+ buf_state |= BM_TAG_VALID | BUF_USAGECOUNT_ONE;
- UnlockBufHdr(buf);
+ UnlockBufHdr(buf, buf_state);
if (oldFlags & BM_TAG_VALID)
{
@@ -1338,12 +1348,15 @@ InvalidateBuffer(BufferDesc *buf)
BufferTag oldTag;
uint32 oldHash; /* hash value for oldTag */
LWLock *oldPartitionLock; /* buffer partition lock for it */
- BufFlags oldFlags;
+ uint32 oldFlags;
+ uint32 buf_state;
/* Save the original buffer tag before dropping the spinlock */
oldTag = buf->tag;
- UnlockBufHdr(buf);
+ buf_state = pg_atomic_read_u32(&buf->state);
+ Assert(buf_state & BM_LOCKED);
+ UnlockBufHdr(buf, buf_state);
/*
* Need to compute the old tag's hashcode and partition lock ID. XXX is it
@@ -1362,12 +1375,12 @@ retry:
LWLockAcquire(oldPartitionLock, LW_EXCLUSIVE);
/* Re-lock the buffer header */
- LockBufHdr(buf);
+ buf_state = LockBufHdr(buf);
/* If it's changed while we were waiting for lock, do nothing */
if (!BUFFERTAGS_EQUAL(buf->tag, oldTag))
{
- UnlockBufHdr(buf);
+ UnlockBufHdr(buf, buf_state);
LWLockRelease(oldPartitionLock);
return;
}
@@ -1381,9 +1394,9 @@ retry:
* yet done StartBufferIO, WaitIO will fall through and we'll effectively
* be busy-looping here.)
*/
- if (buf->refcount != 0)
+ if (BUF_STATE_GET_REFCOUNT(buf_state) != 0)
{
- UnlockBufHdr(buf);
+ UnlockBufHdr(buf, buf_state);
LWLockRelease(oldPartitionLock);
/* safety check: should definitely not be our *own* pin */
if (GetPrivateRefCount(BufferDescriptorGetBuffer(buf)) > 0)
@@ -1396,12 +1409,10 @@ retry:
* Clear out the buffer's tag and flags. We must do this to ensure that
* linear scans of the buffer array don't think the buffer is valid.
*/
- oldFlags = buf->flags;
+ oldFlags = buf_state & BUF_FLAG_MASK;
CLEAR_BUFFERTAG(buf->tag);
- buf->flags = 0;
- buf->usage_count = 0;
-
- UnlockBufHdr(buf);
+ buf_state &= ~(BUF_FLAG_MASK | BUF_USAGECOUNT_MASK);
+ UnlockBufHdr(buf, buf_state);
/*
* Remove the buffer from the lookup hashtable, if it was in there.
@@ -1433,6 +1444,8 @@ void
MarkBufferDirty(Buffer buffer)
{
BufferDesc *bufHdr;
+ uint32 buf_state;
+ uint32 old_buf_state;
if (!BufferIsValid(buffer))
elog(ERROR, "bad buffer ID: %d", buffer);
@@ -1449,24 +1462,32 @@ MarkBufferDirty(Buffer buffer)
/* unfortunately we can't check if the lock is held exclusively */
Assert(LWLockHeldByMe(BufferDescriptorGetContentLock(bufHdr)));
- LockBufHdr(bufHdr);
+ old_buf_state = pg_atomic_read_u32(&bufHdr->state);
+ for (;;)
+ {
+ if (old_buf_state & BM_LOCKED)
+ old_buf_state = WaitBufHdrUnlocked(bufHdr);
- Assert(bufHdr->refcount > 0);
+ buf_state = old_buf_state;
+
+ Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
+ buf_state |= BM_DIRTY | BM_JUST_DIRTIED;
+
+ if (pg_atomic_compare_exchange_u32(&bufHdr->state, &old_buf_state,
+ buf_state))
+ break;
+ }
/*
* If the buffer was not dirty already, do vacuum accounting.
*/
- if (!(bufHdr->flags & BM_DIRTY))
+ if (!(old_buf_state & BM_DIRTY))
{
VacuumPageDirty++;
pgBufferUsage.shared_blks_dirtied++;
if (VacuumCostActive)
VacuumCostBalance += VacuumCostPageDirty;
}
-
- bufHdr->flags |= (BM_DIRTY | BM_JUST_DIRTIED);
-
- UnlockBufHdr(bufHdr);
}
/*
@@ -1531,6 +1552,10 @@ ReleaseAndReadBuffer(Buffer buffer,
*
* This should be applied only to shared buffers, never local ones.
*
+ * Since buffers are pinned/unpinned very frequently, pin buffers without
+ * taking the buffer header lock; instead update the state variable in loop of
+ * CAS operations. Hopefully it's just a single CAS.
+ *
* Note that ResourceOwnerEnlargeBuffers must have been done already.
*
* Returns TRUE if buffer is BM_VALID, else FALSE. This provision allows
@@ -1547,23 +1572,34 @@ PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy)
if (ref == NULL)
{
+ uint32 buf_state;
+ uint32 old_buf_state;
+
ReservePrivateRefCountEntry();
ref = NewPrivateRefCountEntry(b);
- LockBufHdr(buf);
- buf->refcount++;
- if (strategy == NULL)
- {
- if (buf->usage_count < BM_MAX_USAGE_COUNT)
- buf->usage_count++;
- }
- else
+ old_buf_state = pg_atomic_read_u32(&buf->state);
+ for (;;)
{
- if (buf->usage_count == 0)
- buf->usage_count = 1;
+ if (old_buf_state & BM_LOCKED)
+ old_buf_state = WaitBufHdrUnlocked(buf);
+
+ buf_state = old_buf_state;
+
+ /* increase refcount */
+ buf_state += BUF_REFCOUNT_ONE;
+
+ /* increase usagecount unless already max */
+ if (BUF_STATE_GET_USAGECOUNT(buf_state) != BM_MAX_USAGE_COUNT)
+ buf_state += BUF_USAGECOUNT_ONE;
+
+ if (pg_atomic_compare_exchange_u32(&buf->state, &old_buf_state,
+ buf_state))
+ {
+ result = (buf_state & BM_VALID) != 0;
+ break;
+ }
}
- result = (buf->flags & BM_VALID) != 0;
- UnlockBufHdr(buf);
}
else
{
@@ -1603,6 +1639,7 @@ PinBuffer_Locked(BufferDesc *buf)
{
Buffer b;
PrivateRefCountEntry *ref;
+ uint32 buf_state;
/*
* As explained, We don't expect any preexisting pins. That allows us to
@@ -1610,8 +1647,14 @@ PinBuffer_Locked(BufferDesc *buf)
*/
Assert(GetPrivateRefCountEntry(BufferDescriptorGetBuffer(buf), false) == NULL);
- buf->refcount++;
- UnlockBufHdr(buf);
+ /*
+ * Since we hold the buffer spinlock, we can update the buffer state and
+ * release the lock in one operation.
+ */
+ buf_state = pg_atomic_read_u32(&buf->state);
+ Assert(buf_state & BM_LOCKED);
+ buf_state += BUF_REFCOUNT_ONE;
+ UnlockBufHdr(buf, buf_state);
b = BufferDescriptorGetBuffer(buf);
@@ -1646,30 +1689,59 @@ UnpinBuffer(BufferDesc *buf, bool fixOwner)
ref->refcount--;
if (ref->refcount == 0)
{
+ uint32 buf_state;
+ uint32 old_buf_state;
+
/* I'd better not still hold any locks on the buffer */
Assert(!LWLockHeldByMe(BufferDescriptorGetContentLock(buf)));
Assert(!LWLockHeldByMe(BufferDescriptorGetIOLock(buf)));
- LockBufHdr(buf);
+ /*
+ * Decrement the shared reference count.
+ *
+ * Since buffer spinlock holder can update status using just write,
+ * it's not safe to use atomic decrement here; thus use a CAS loop.
+ */
+ old_buf_state = pg_atomic_read_u32(&buf->state);
+ for (;;)
+ {
+ if (old_buf_state & BM_LOCKED)
+ old_buf_state = WaitBufHdrUnlocked(buf);
+
+ buf_state = old_buf_state;
+
+ buf_state -= BUF_REFCOUNT_ONE;
- /* Decrement the shared reference count */
- Assert(buf->refcount > 0);
- buf->refcount--;
+ if (pg_atomic_compare_exchange_u32(&buf->state, &old_buf_state,
+ buf_state))
+ break;
+ }
/* Support LockBufferForCleanup() */
- if ((buf->flags & BM_PIN_COUNT_WAITER) &&
- buf->refcount == 1)
+ if (buf_state & BM_PIN_COUNT_WAITER)
{
- /* we just released the last pin other than the waiter's */
- int wait_backend_pid = buf->wait_backend_pid;
+ /*
+ * Acquire the buffer header lock, re-check that there's a waiter.
+ * Another backend could have unpinned this buffer, and already
+ * woken up the waiter. There's no danger of the buffer being
+ * replaced after we unpinned it above, as it's pinned by the
+ * waiter.
+ */
+ buf_state = LockBufHdr(buf);
- buf->flags &= ~BM_PIN_COUNT_WAITER;
- UnlockBufHdr(buf);
- ProcSendSignal(wait_backend_pid);
- }
- else
- UnlockBufHdr(buf);
+ if ((buf_state & BM_PIN_COUNT_WAITER) &&
+ BUF_STATE_GET_REFCOUNT(buf_state) == 1)
+ {
+ /* we just released the last pin other than the waiter's */
+ int wait_backend_pid = buf->wait_backend_pid;
+ buf_state &= ~BM_PIN_COUNT_WAITER;
+ UnlockBufHdr(buf, buf_state);
+ ProcSendSignal(wait_backend_pid);
+ }
+ else
+ UnlockBufHdr(buf, buf_state);
+ }
ForgetPrivateRefCountEntry(ref);
}
}
@@ -1687,6 +1759,7 @@ UnpinBuffer(BufferDesc *buf, bool fixOwner)
static void
BufferSync(int flags)
{
+ uint32 buf_state;
int buf_id;
int num_to_scan;
int num_spaces;
@@ -1736,13 +1809,13 @@ BufferSync(int flags)
* Header spinlock is enough to examine BM_DIRTY, see comment in
* SyncOneBuffer.
*/
- LockBufHdr(bufHdr);
+ buf_state = LockBufHdr(bufHdr);
- if ((bufHdr->flags & mask) == mask)
+ if ((buf_state & mask) == mask)
{
CkptSortItem *item;
- bufHdr->flags |= BM_CHECKPOINT_NEEDED;
+ buf_state |= BM_CHECKPOINT_NEEDED;
item = &CkptBufferIds[num_to_scan++];
item->buf_id = buf_id;
@@ -1752,7 +1825,7 @@ BufferSync(int flags)
item->blockNum = bufHdr->tag.blockNum;
}
- UnlockBufHdr(bufHdr);
+ UnlockBufHdr(bufHdr, buf_state);
}
if (num_to_scan == 0)
@@ -1888,7 +1961,7 @@ BufferSync(int flags)
* write the buffer though we didn't need to. It doesn't seem worth
* guarding against this, though.
*/
- if (bufHdr->flags & BM_CHECKPOINT_NEEDED)
+ if (pg_atomic_read_u32(&bufHdr->state) & BM_CHECKPOINT_NEEDED)
{
if (SyncOneBuffer(buf_id, false, &wb_context) & BUF_WRITTEN)
{
@@ -2176,8 +2249,8 @@ BgBufferSync(WritebackContext *wb_context)
/* Execute the LRU scan */
while (num_to_scan > 0 && reusable_buffers < upcoming_alloc_est)
{
- int buffer_state = SyncOneBuffer(next_to_clean, true,
- wb_context);
+ int sync_state = SyncOneBuffer(next_to_clean, true,
+ wb_context);
if (++next_to_clean >= NBuffers)
{
@@ -2186,7 +2259,7 @@ BgBufferSync(WritebackContext *wb_context)
}
num_to_scan--;
- if (buffer_state & BUF_WRITTEN)
+ if (sync_state & BUF_WRITTEN)
{
reusable_buffers++;
if (++num_written >= bgwriter_lru_maxpages)
@@ -2195,7 +2268,7 @@ BgBufferSync(WritebackContext *wb_context)
break;
}
}
- else if (buffer_state & BUF_REUSABLE)
+ else if (sync_state & BUF_REUSABLE)
reusable_buffers++;
}
@@ -2258,6 +2331,7 @@ SyncOneBuffer(int buf_id, bool skip_recently_used, WritebackContext *wb_context)
{
BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
int result = 0;
+ uint32 buf_state;
BufferTag tag;
ReservePrivateRefCountEntry();
@@ -2271,21 +2345,24 @@ SyncOneBuffer(int buf_id, bool skip_recently_used, WritebackContext *wb_context)
* don't worry because our checkpoint.redo points before log record for
* upcoming changes and so we are not required to write such dirty buffer.
*/
- LockBufHdr(bufHdr);
+ buf_state = LockBufHdr(bufHdr);
- if (bufHdr->refcount == 0 && bufHdr->usage_count == 0)
+ if (BUF_STATE_GET_REFCOUNT(buf_state) == 0 &&
+ BUF_STATE_GET_USAGECOUNT(buf_state) == 0)
+ {
result |= BUF_REUSABLE;
+ }
else if (skip_recently_used)
{
/* Caller told us not to write recently-used buffers */
- UnlockBufHdr(bufHdr);
+ UnlockBufHdr(bufHdr, buf_state);
return result;
}
- if (!(bufHdr->flags & BM_VALID) || !(bufHdr->flags & BM_DIRTY))
+ if (!(buf_state & BM_VALID) || !(buf_state & BM_DIRTY))
{
/* It's clean, so nothing to do */
- UnlockBufHdr(bufHdr);
+ UnlockBufHdr(bufHdr, buf_state);
return result;
}
@@ -2439,6 +2516,7 @@ PrintBufferLeakWarning(Buffer buffer)
int32 loccount;
char *path;
BackendId backend;
+ uint32 buf_state;
Assert(BufferIsValid(buffer));
if (BufferIsLocal(buffer))
@@ -2456,12 +2534,13 @@ PrintBufferLeakWarning(Buffer buffer)
/* theoretically we should lock the bufhdr here */
path = relpathbackend(buf->tag.rnode, backend, buf->tag.forkNum);
+ buf_state = pg_atomic_read_u32(&buf->state);
elog(WARNING,
"buffer refcount leak: [%03d] "
"(rel=%s, blockNum=%u, flags=0x%x, refcount=%u %d)",
buffer, path,
- buf->tag.blockNum, buf->flags,
- buf->refcount, loccount);
+ buf->tag.blockNum, buf_state & BUF_FLAG_MASK,
+ BUF_STATE_GET_REFCOUNT(buf_state), loccount);
pfree(path);
}
@@ -2573,6 +2652,7 @@ FlushBuffer(BufferDesc *buf, SMgrRelation reln)
io_time;
Block bufBlock;
char *bufToWrite;
+ uint32 buf_state;
/*
* Acquire the buffer's io_in_progress lock. If StartBufferIO returns
@@ -2598,7 +2678,7 @@ FlushBuffer(BufferDesc *buf, SMgrRelation reln)
reln->smgr_rnode.node.dbNode,
reln->smgr_rnode.node.relNode);
- LockBufHdr(buf);
+ buf_state = LockBufHdr(buf);
/*
* Run PageGetLSN while holding header lock, since we don't have the
@@ -2607,8 +2687,8 @@ FlushBuffer(BufferDesc *buf, SMgrRelation reln)
recptr = BufferGetLSN(buf);
/* To check if block content changes while flushing. - vadim 01/17/97 */
- buf->flags &= ~BM_JUST_DIRTIED;
- UnlockBufHdr(buf);
+ buf_state &= ~BM_JUST_DIRTIED;
+ UnlockBufHdr(buf, buf_state);
/*
* Force XLOG flush up to buffer's LSN. This implements the basic WAL
@@ -2627,7 +2707,7 @@ FlushBuffer(BufferDesc *buf, SMgrRelation reln)
* disastrous system-wide consequences. To make sure that can't happen,
* skip the flush if the buffer isn't permanent.
*/
- if (buf->flags & BM_PERMANENT)
+ if (buf_state & BM_PERMANENT)
XLogFlush(recptr);
/*
@@ -2716,12 +2796,12 @@ BufferIsPermanent(Buffer buffer)
/*
* BM_PERMANENT can't be changed while we hold a pin on the buffer, so we
* need not bother with the buffer header spinlock. Even if someone else
- * changes the buffer header flags while we're doing this, we assume that
- * changing an aligned 2-byte BufFlags value is atomic, so we'll read the
- * old value or the new value, but not random garbage.
+ * changes the buffer header state while we're doing this, the state is
+ * changed atomically, so we'll read the old value or the new value, but
+ * not random garbage.
*/
bufHdr = GetBufferDescriptor(buffer - 1);
- return (bufHdr->flags & BM_PERMANENT) != 0;
+ return (pg_atomic_read_u32(&bufHdr->state) & BM_PERMANENT) != 0;
}
/*
@@ -2736,6 +2816,7 @@ BufferGetLSNAtomic(Buffer buffer)
BufferDesc *bufHdr = GetBufferDescriptor(buffer - 1);
char *page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
XLogRecPtr lsn;
+ uint32 buf_state;
/*
* If we don't need locking for correctness, fastpath out.
@@ -2747,9 +2828,9 @@ BufferGetLSNAtomic(Buffer buffer)
Assert(BufferIsValid(buffer));
Assert(BufferIsPinned(buffer));
- LockBufHdr(bufHdr);
+ buf_state = LockBufHdr(bufHdr);
lsn = PageGetLSN(page);
- UnlockBufHdr(bufHdr);
+ UnlockBufHdr(bufHdr, buf_state);
return lsn;
}
@@ -2797,6 +2878,7 @@ DropRelFileNodeBuffers(RelFileNodeBackend rnode, ForkNumber forkNum,
for (i = 0; i < NBuffers; i++)
{
BufferDesc *bufHdr = GetBufferDescriptor(i);
+ uint32 buf_state;
/*
* We can make this a tad faster by prechecking the buffer tag before
@@ -2817,13 +2899,13 @@ DropRelFileNodeBuffers(RelFileNodeBackend rnode, ForkNumber forkNum,
if (!RelFileNodeEquals(bufHdr->tag.rnode, rnode.node))
continue;
- LockBufHdr(bufHdr);
+ buf_state = LockBufHdr(bufHdr);
if (RelFileNodeEquals(bufHdr->tag.rnode, rnode.node) &&
bufHdr->tag.forkNum == forkNum &&
bufHdr->tag.blockNum >= firstDelBlock)
InvalidateBuffer(bufHdr); /* releases spinlock */
else
- UnlockBufHdr(bufHdr);
+ UnlockBufHdr(bufHdr, buf_state);
}
}
@@ -2887,6 +2969,7 @@ DropRelFileNodesAllBuffers(RelFileNodeBackend *rnodes, int nnodes)
{
RelFileNode *rnode = NULL;
BufferDesc *bufHdr = GetBufferDescriptor(i);
+ uint32 buf_state;
/*
* As in DropRelFileNodeBuffers, an unlocked precheck should be safe
@@ -2917,11 +3000,11 @@ DropRelFileNodesAllBuffers(RelFileNodeBackend *rnodes, int nnodes)
if (rnode == NULL)
continue;
- LockBufHdr(bufHdr);
+ buf_state = LockBufHdr(bufHdr);
if (RelFileNodeEquals(bufHdr->tag.rnode, (*rnode)))
InvalidateBuffer(bufHdr); /* releases spinlock */
else
- UnlockBufHdr(bufHdr);
+ UnlockBufHdr(bufHdr, buf_state);
}
pfree(nodes);
@@ -2951,6 +3034,7 @@ DropDatabaseBuffers(Oid dbid)
for (i = 0; i < NBuffers; i++)
{
BufferDesc *bufHdr = GetBufferDescriptor(i);
+ uint32 buf_state;
/*
* As in DropRelFileNodeBuffers, an unlocked precheck should be safe
@@ -2959,11 +3043,11 @@ DropDatabaseBuffers(Oid dbid)
if (bufHdr->tag.rnode.dbNode != dbid)
continue;
- LockBufHdr(bufHdr);
+ buf_state = LockBufHdr(bufHdr);
if (bufHdr->tag.rnode.dbNode == dbid)
InvalidateBuffer(bufHdr); /* releases spinlock */
else
- UnlockBufHdr(bufHdr);
+ UnlockBufHdr(bufHdr, buf_state);
}
}
@@ -3055,9 +3139,12 @@ FlushRelationBuffers(Relation rel)
{
for (i = 0; i < NLocBuffer; i++)
{
+ uint32 buf_state;
+
bufHdr = GetLocalBufferDescriptor(i);
if (RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node) &&
- (bufHdr->flags & BM_VALID) && (bufHdr->flags & BM_DIRTY))
+ ((buf_state = pg_atomic_read_u32(&bufHdr->state)) &
+ (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
{
ErrorContextCallback errcallback;
Page localpage;
@@ -3078,7 +3165,8 @@ FlushRelationBuffers(Relation rel)
localpage,
false);
- bufHdr->flags &= ~(BM_DIRTY | BM_JUST_DIRTIED);
+ buf_state &= ~(BM_DIRTY | BM_JUST_DIRTIED);
+ pg_atomic_write_u32(&bufHdr->state, buf_state);
/* Pop the error context stack */
error_context_stack = errcallback.previous;
@@ -3093,6 +3181,8 @@ FlushRelationBuffers(Relation rel)
for (i = 0; i < NBuffers; i++)
{
+ uint32 buf_state;
+
bufHdr = GetBufferDescriptor(i);
/*
@@ -3104,9 +3194,9 @@ FlushRelationBuffers(Relation rel)
ReservePrivateRefCountEntry();
- LockBufHdr(bufHdr);
+ buf_state = LockBufHdr(bufHdr);
if (RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node) &&
- (bufHdr->flags & BM_VALID) && (bufHdr->flags & BM_DIRTY))
+ (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
{
PinBuffer_Locked(bufHdr);
LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
@@ -3115,7 +3205,7 @@ FlushRelationBuffers(Relation rel)
UnpinBuffer(bufHdr, true);
}
else
- UnlockBufHdr(bufHdr);
+ UnlockBufHdr(bufHdr, buf_state);
}
}
@@ -3145,6 +3235,8 @@ FlushDatabaseBuffers(Oid dbid)
for (i = 0; i < NBuffers; i++)
{
+ uint32 buf_state;
+
bufHdr = GetBufferDescriptor(i);
/*
@@ -3156,9 +3248,9 @@ FlushDatabaseBuffers(Oid dbid)
ReservePrivateRefCountEntry();
- LockBufHdr(bufHdr);
+ buf_state = LockBufHdr(bufHdr);
if (bufHdr->tag.rnode.dbNode == dbid &&
- (bufHdr->flags & BM_VALID) && (bufHdr->flags & BM_DIRTY))
+ (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
{
PinBuffer_Locked(bufHdr);
LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
@@ -3167,7 +3259,7 @@ FlushDatabaseBuffers(Oid dbid)
UnpinBuffer(bufHdr, true);
}
else
- UnlockBufHdr(bufHdr);
+ UnlockBufHdr(bufHdr, buf_state);
}
}
@@ -3297,12 +3389,13 @@ MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
* is only intended to be used in cases where failing to write out the
* data would be harmless anyway, it doesn't really matter.
*/
- if ((bufHdr->flags & (BM_DIRTY | BM_JUST_DIRTIED)) !=
+ if ((pg_atomic_read_u32(&bufHdr->state) & (BM_DIRTY | BM_JUST_DIRTIED)) !=
(BM_DIRTY | BM_JUST_DIRTIED))
{
XLogRecPtr lsn = InvalidXLogRecPtr;
bool dirtied = false;
bool delayChkpt = false;
+ uint32 buf_state;
/*
* If we need to protect hint bit updates from torn writes, WAL-log a
@@ -3313,7 +3406,8 @@ MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
* We don't check full_page_writes here because that logic is included
* when we call XLogInsert() since the value changes dynamically.
*/
- if (XLogHintBitIsNeeded() && (bufHdr->flags & BM_PERMANENT))
+ if (XLogHintBitIsNeeded() &&
+ (pg_atomic_read_u32(&bufHdr->state) & BM_PERMANENT))
{
/*
* If we're in recovery we cannot dirty a page because of a hint.
@@ -3352,9 +3446,11 @@ MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
lsn = XLogSaveBufferForHint(buffer, buffer_std);
}
- LockBufHdr(bufHdr);
- Assert(bufHdr->refcount > 0);
- if (!(bufHdr->flags & BM_DIRTY))
+ buf_state = LockBufHdr(bufHdr);
+
+ Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
+
+ if (!(buf_state & BM_DIRTY))
{
dirtied = true; /* Means "will be dirtied by this action" */
@@ -3374,8 +3470,9 @@ MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
if (!XLogRecPtrIsInvalid(lsn))
PageSetLSN(page, lsn);
}
- bufHdr->flags |= (BM_DIRTY | BM_JUST_DIRTIED);
- UnlockBufHdr(bufHdr);
+
+ buf_state |= BM_DIRTY | BM_JUST_DIRTIED;
+ UnlockBufHdr(bufHdr, buf_state);
if (delayChkpt)
MyPgXact->delayChkpt = false;
@@ -3406,17 +3503,19 @@ UnlockBuffers(void)
if (buf)
{
- LockBufHdr(buf);
+ uint32 buf_state;
+
+ buf_state = LockBufHdr(buf);
/*
* Don't complain if flag bit not set; it could have been reset but we
* got a cancel/die interrupt before getting the signal.
*/
- if ((buf->flags & BM_PIN_COUNT_WAITER) != 0 &&
+ if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
buf->wait_backend_pid == MyProcPid)
- buf->flags &= ~BM_PIN_COUNT_WAITER;
+ buf_state &= ~BM_PIN_COUNT_WAITER;
- UnlockBufHdr(buf);
+ UnlockBufHdr(buf, buf_state);
PinCountWaitBuf = NULL;
}
@@ -3509,27 +3608,30 @@ LockBufferForCleanup(Buffer buffer)
for (;;)
{
+ uint32 buf_state;
+
/* Try to acquire lock */
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
- LockBufHdr(bufHdr);
- Assert(bufHdr->refcount > 0);
- if (bufHdr->refcount == 1)
+ buf_state = LockBufHdr(bufHdr);
+
+ Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
+ if (BUF_STATE_GET_REFCOUNT(buf_state) == 1)
{
/* Successfully acquired exclusive lock with pincount 1 */
- UnlockBufHdr(bufHdr);
+ UnlockBufHdr(bufHdr, buf_state);
return;
}
/* Failed, so mark myself as waiting for pincount 1 */
- if (bufHdr->flags & BM_PIN_COUNT_WAITER)
+ if (buf_state & BM_PIN_COUNT_WAITER)
{
- UnlockBufHdr(bufHdr);
+ UnlockBufHdr(bufHdr, buf_state);
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
elog(ERROR, "multiple backends attempting to wait for pincount 1");
}
bufHdr->wait_backend_pid = MyProcPid;
- bufHdr->flags |= BM_PIN_COUNT_WAITER;
PinCountWaitBuf = bufHdr;
- UnlockBufHdr(bufHdr);
+ buf_state |= BM_PIN_COUNT_WAITER;
+ UnlockBufHdr(bufHdr, buf_state);
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
/* Report the wait */
@@ -3558,11 +3660,11 @@ LockBufferForCleanup(Buffer buffer)
* impossible with the current usages due to table level locking, but
* better be safe.
*/
- LockBufHdr(bufHdr);
- if ((bufHdr->flags & BM_PIN_COUNT_WAITER) != 0 &&
+ buf_state = LockBufHdr(bufHdr);
+ if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
bufHdr->wait_backend_pid == MyProcPid)
- bufHdr->flags &= ~BM_PIN_COUNT_WAITER;
- UnlockBufHdr(bufHdr);
+ buf_state &= ~BM_PIN_COUNT_WAITER;
+ UnlockBufHdr(bufHdr, buf_state);
PinCountWaitBuf = NULL;
/* Loop back and try again */
@@ -3603,22 +3705,26 @@ bool
ConditionalLockBufferForCleanup(Buffer buffer)
{
BufferDesc *bufHdr;
+ uint32 buf_state,
+ refcount;
Assert(BufferIsValid(buffer));
if (BufferIsLocal(buffer))
{
+ refcount = LocalRefCount[-buffer - 1];
/* There should be exactly one pin */
- Assert(LocalRefCount[-buffer - 1] > 0);
- if (LocalRefCount[-buffer - 1] != 1)
+ Assert(refcount > 0);
+ if (refcount != 1)
return false;
/* Nobody else to wait for */
return true;
}
/* There should be exactly one local pin */
- Assert(GetPrivateRefCount(buffer) > 0);
- if (GetPrivateRefCount(buffer) != 1)
+ refcount = GetPrivateRefCount(buffer);
+ Assert(refcount);
+ if (refcount != 1)
return false;
/* Try to acquire lock */
@@ -3626,17 +3732,19 @@ ConditionalLockBufferForCleanup(Buffer buffer)
return false;
bufHdr = GetBufferDescriptor(buffer - 1);
- LockBufHdr(bufHdr);
- Assert(bufHdr->refcount > 0);
- if (bufHdr->refcount == 1)
+ buf_state = LockBufHdr(bufHdr);
+ refcount = BUF_STATE_GET_REFCOUNT(buf_state);
+
+ Assert(refcount > 0);
+ if (refcount == 1)
{
/* Successfully acquired exclusive lock with pincount 1 */
- UnlockBufHdr(bufHdr);
+ UnlockBufHdr(bufHdr, buf_state);
return true;
}
/* Failed, so release the lock */
- UnlockBufHdr(bufHdr);
+ UnlockBufHdr(bufHdr, buf_state);
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
return false;
}
@@ -3666,17 +3774,17 @@ WaitIO(BufferDesc *buf)
*/
for (;;)
{
- BufFlags sv_flags;
+ uint32 buf_state;
/*
* It may not be necessary to acquire the spinlock to check the flag
* here, but since this test is essential for correctness, we'd better
* play it safe.
*/
- LockBufHdr(buf);
- sv_flags = buf->flags;
- UnlockBufHdr(buf);
- if (!(sv_flags & BM_IO_IN_PROGRESS))
+ buf_state = LockBufHdr(buf);
+ UnlockBufHdr(buf, buf_state);
+
+ if (!(buf_state & BM_IO_IN_PROGRESS))
break;
LWLockAcquire(BufferDescriptorGetIOLock(buf), LW_SHARED);
LWLockRelease(BufferDescriptorGetIOLock(buf));
@@ -3704,6 +3812,8 @@ WaitIO(BufferDesc *buf)
static bool
StartBufferIO(BufferDesc *buf, bool forInput)
{
+ uint32 buf_state;
+
Assert(!InProgressBuf);
for (;;)
@@ -3714,9 +3824,9 @@ StartBufferIO(BufferDesc *buf, bool forInput)
*/
LWLockAcquire(BufferDescriptorGetIOLock(buf), LW_EXCLUSIVE);
- LockBufHdr(buf);
+ buf_state = LockBufHdr(buf);
- if (!(buf->flags & BM_IO_IN_PROGRESS))
+ if (!(buf_state & BM_IO_IN_PROGRESS))
break;
/*
@@ -3725,24 +3835,23 @@ StartBufferIO(BufferDesc *buf, bool forInput)
* an error (see AbortBufferIO). If that's the case, we must wait for
* him to get unwedged.
*/
- UnlockBufHdr(buf);
+ UnlockBufHdr(buf, buf_state);
LWLockRelease(BufferDescriptorGetIOLock(buf));
WaitIO(buf);
}
/* Once we get here, there is definitely no I/O active on this buffer */
- if (forInput ? (buf->flags & BM_VALID) : !(buf->flags & BM_DIRTY))
+ if (forInput ? (buf_state & BM_VALID) : !(buf_state & BM_DIRTY))
{
/* someone else already did the I/O */
- UnlockBufHdr(buf);
+ UnlockBufHdr(buf, buf_state);
LWLockRelease(BufferDescriptorGetIOLock(buf));
return false;
}
- buf->flags |= BM_IO_IN_PROGRESS;
-
- UnlockBufHdr(buf);
+ buf_state |= BM_IO_IN_PROGRESS;
+ UnlockBufHdr(buf, buf_state);
InProgressBuf = buf;
IsForInput = forInput;
@@ -3768,19 +3877,22 @@ StartBufferIO(BufferDesc *buf, bool forInput)
* be 0, or BM_VALID if we just finished reading in the page.
*/
static void
-TerminateBufferIO(BufferDesc *buf, bool clear_dirty, int set_flag_bits)
+TerminateBufferIO(BufferDesc *buf, bool clear_dirty, uint32 set_flag_bits)
{
+ uint32 buf_state;
+
Assert(buf == InProgressBuf);
- LockBufHdr(buf);
+ buf_state = LockBufHdr(buf);
+
+ Assert(buf_state & BM_IO_IN_PROGRESS);
- Assert(buf->flags & BM_IO_IN_PROGRESS);
- buf->flags &= ~(BM_IO_IN_PROGRESS | BM_IO_ERROR);
- if (clear_dirty && !(buf->flags & BM_JUST_DIRTIED))
- buf->flags &= ~(BM_DIRTY | BM_CHECKPOINT_NEEDED);
- buf->flags |= set_flag_bits;
+ buf_state &= ~(BM_IO_IN_PROGRESS | BM_IO_ERROR);
+ if (clear_dirty && !(buf_state & BM_JUST_DIRTIED))
+ buf_state &= ~(BM_DIRTY | BM_CHECKPOINT_NEEDED);
- UnlockBufHdr(buf);
+ buf_state |= set_flag_bits;
+ UnlockBufHdr(buf, buf_state);
InProgressBuf = NULL;
@@ -3803,6 +3915,8 @@ AbortBufferIO(void)
if (buf)
{
+ uint32 buf_state;
+
/*
* Since LWLockReleaseAll has already been called, we're not holding
* the buffer's io_in_progress_lock. We have to re-acquire it so that
@@ -3811,24 +3925,22 @@ AbortBufferIO(void)
*/
LWLockAcquire(BufferDescriptorGetIOLock(buf), LW_EXCLUSIVE);
- LockBufHdr(buf);
- Assert(buf->flags & BM_IO_IN_PROGRESS);
+ buf_state = LockBufHdr(buf);
+ Assert(buf_state & BM_IO_IN_PROGRESS);
if (IsForInput)
{
- Assert(!(buf->flags & BM_DIRTY));
+ Assert(!(buf_state & BM_DIRTY));
+
/* We'd better not think buffer is valid yet */
- Assert(!(buf->flags & BM_VALID));
- UnlockBufHdr(buf);
+ Assert(!(buf_state & BM_VALID));
+ UnlockBufHdr(buf, buf_state);
}
else
{
- BufFlags sv_flags;
-
- sv_flags = buf->flags;
- Assert(sv_flags & BM_DIRTY);
- UnlockBufHdr(buf);
+ Assert(buf_state & BM_DIRTY);
+ UnlockBufHdr(buf, buf_state);
/* Issue notice if this is not the first failure... */
- if (sv_flags & BM_IO_ERROR)
+ if (buf_state & BM_IO_ERROR)
{
/* Buffer is pinned, so we can read tag without spinlock */
char *path;
@@ -3912,6 +4024,54 @@ rnode_comparator(const void *p1, const void *p2)
}
/*
+ * Lock buffer header - set BM_LOCKED in buffer state.
+ */
+uint32
+LockBufHdr(BufferDesc *desc)
+{
+ SpinDelayStatus delayStatus = init_spin_delay(desc);
+ uint32 old_buf_state;
+
+ while (true)
+ {
+ /* set BM_LOCKED flag */
+ old_buf_state = pg_atomic_fetch_or_u32(&desc->state, BM_LOCKED);
+ /* if it wasn't set before we're OK */
+ if (!(old_buf_state & BM_LOCKED))
+ break;
+ perform_spin_delay(&delayStatus);
+ }
+ finish_spin_delay(&delayStatus);
+ return old_buf_state | BM_LOCKED;
+}
+
+/*
+ * Wait until the BM_LOCKED flag isn't set anymore and return the buffer's
+ * state at that point.
+ *
+ * Obviously the buffer could be locked by the time the value is returned, so
+ * this is primarily useful in CAS style loops.
+ */
+static uint32
+WaitBufHdrUnlocked(BufferDesc *buf)
+{
+ SpinDelayStatus delayStatus = init_spin_delay(buf);
+ uint32 buf_state;
+
+ buf_state = pg_atomic_read_u32(&buf->state);
+
+ while (buf_state & BM_LOCKED)
+ {
+ perform_spin_delay(&delayStatus);
+ buf_state = pg_atomic_read_u32(&buf->state);
+ }
+
+ finish_spin_delay(&delayStatus);
+
+ return buf_state;
+}
+
+/*
* BufferTag comparator.
*/
static int
generated by cgit v1.2.3 (git 2.25.1) at 2025-05-23 12:14:22 +0000