diff options
Diffstat (limited to 'src/backend/storage/buffer/freelist.c')
| -rw-r--r-- | src/backend/storage/buffer/freelist.c | 44 |
1 files changed, 27 insertions, 17 deletions
diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 551d15205ca..88b90dc5276 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -98,7 +98,8 @@ typedef struct BufferAccessStrategyData /* Prototypes for internal functions */ -static BufferDesc *GetBufferFromRing(BufferAccessStrategy strategy); +static BufferDesc *GetBufferFromRing(BufferAccessStrategy strategy, + uint32 *buf_state); static void AddBufferToRing(BufferAccessStrategy strategy, BufferDesc *buf); @@ -180,11 +181,12 @@ ClockSweepTick(void) * return the buffer with the buffer header spinlock still held. */ BufferDesc * -StrategyGetBuffer(BufferAccessStrategy strategy) +StrategyGetBuffer(BufferAccessStrategy strategy, uint32 *buf_state) { BufferDesc *buf; int bgwprocno; int trycounter; + uint32 local_buf_state; /* to avoid repeated (de-)referencing */ /* * If given a strategy object, see whether it can select a buffer. We @@ -192,7 +194,7 @@ StrategyGetBuffer(BufferAccessStrategy strategy) */ if (strategy != NULL) { - buf = GetBufferFromRing(strategy); + buf = GetBufferFromRing(strategy, buf_state); if (buf != NULL) return buf; } @@ -279,14 +281,16 @@ StrategyGetBuffer(BufferAccessStrategy strategy) * it before we got to it. It's probably impossible altogether as * of 8.3, but we'd better check anyway.) */ - LockBufHdr(buf); - if (buf->refcount == 0 && buf->usage_count == 0) + local_buf_state = LockBufHdr(buf); + if (BUF_STATE_GET_REFCOUNT(local_buf_state) == 0 + && BUF_STATE_GET_USAGECOUNT(local_buf_state) == 0) { if (strategy != NULL) AddBufferToRing(strategy, buf); + *buf_state = local_buf_state; return buf; } - UnlockBufHdr(buf); + UnlockBufHdr(buf, local_buf_state); } } @@ -295,19 +299,20 @@ StrategyGetBuffer(BufferAccessStrategy strategy) trycounter = NBuffers; for (;;) { - buf = GetBufferDescriptor(ClockSweepTick()); /* * If the buffer is pinned or has a nonzero usage_count, we cannot use * it; decrement the usage_count (unless pinned) and keep scanning. */ - LockBufHdr(buf); - if (buf->refcount == 0) + local_buf_state = LockBufHdr(buf); + + if (BUF_STATE_GET_REFCOUNT(local_buf_state) == 0) { - if (buf->usage_count > 0) + if (BUF_STATE_GET_USAGECOUNT(local_buf_state) != 0) { - buf->usage_count--; + local_buf_state -= BUF_USAGECOUNT_ONE; + trycounter = NBuffers; } else @@ -315,6 +320,7 @@ StrategyGetBuffer(BufferAccessStrategy strategy) /* Found a usable buffer */ if (strategy != NULL) AddBufferToRing(strategy, buf); + *buf_state = local_buf_state; return buf; } } @@ -327,10 +333,10 @@ StrategyGetBuffer(BufferAccessStrategy strategy) * probably better to fail than to risk getting stuck in an * infinite loop. */ - UnlockBufHdr(buf); + UnlockBufHdr(buf, local_buf_state); elog(ERROR, "no unpinned buffers available"); } - UnlockBufHdr(buf); + UnlockBufHdr(buf, local_buf_state); } } @@ -585,10 +591,12 @@ FreeAccessStrategy(BufferAccessStrategy strategy) * The bufhdr spin lock is held on the returned buffer. */ static BufferDesc * -GetBufferFromRing(BufferAccessStrategy strategy) +GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state) { BufferDesc *buf; Buffer bufnum; + uint32 local_buf_state; /* to avoid repeated (de-)referencing */ + /* Advance to next ring slot */ if (++strategy->current >= strategy->ring_size) @@ -616,13 +624,15 @@ GetBufferFromRing(BufferAccessStrategy strategy) * shouldn't re-use it. */ buf = GetBufferDescriptor(bufnum - 1); - LockBufHdr(buf); - if (buf->refcount == 0 && buf->usage_count <= 1) + local_buf_state = LockBufHdr(buf); + if (BUF_STATE_GET_REFCOUNT(local_buf_state) == 0 + && BUF_STATE_GET_USAGECOUNT(local_buf_state) <= 1) { strategy->current_was_in_ring = true; + *buf_state = local_buf_state; return buf; } - UnlockBufHdr(buf); + UnlockBufHdr(buf, local_buf_state); /* * Tell caller to allocate a new buffer with the normal allocation |