On Wed, Jan 4, 2012 at 11:14 AM, Simon Riggs <si...@2ndquadrant.com> wrote:
> Not having a freelist at all is probably a simpler way of avoiding the
> lock contention, so I'll happily back that suggestion instead. Patch
> attached, previous patch revoked.
v2 attached with cleanup of some random stuff that crept onto patch.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c
index 94cefba..9332a74 100644
--- a/src/backend/storage/buffer/buf_init.c
+++ b/src/backend/storage/buffer/buf_init.c
@@ -115,7 +115,7 @@ InitBufferPool(void)
* Initially link all the buffers together as unused. Subsequent
* management of this list is done by freelist.c.
*/
- buf->freeNext = i + 1;
+ StrategyInitFreelistBuffer(buf);
buf->io_in_progress_lock = LWLockAssign();
buf->content_lock = LWLockAssign();
diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 3e62448..6b49cae 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -27,6 +27,7 @@ typedef struct
/* Clock sweep hand: index of next buffer to consider grabbing */
int nextVictimBuffer;
+#ifdef USE_BUFMGR_FREELIST
int firstFreeBuffer; /* Head of list of unused buffers */
int lastFreeBuffer; /* Tail of list of unused buffers */
@@ -34,7 +35,7 @@ typedef struct
* NOTE: lastFreeBuffer is undefined when firstFreeBuffer is -1 (that is,
* when the list is empty)
*/
-
+#endif
/*
* Statistics. These counters should be wide enough that they can't
* overflow during a single bgwriter cycle.
@@ -134,6 +135,7 @@ StrategyGetBuffer(BufferAccessStrategy strategy, bool *lock_held)
*/
StrategyControl->numBufferAllocs++;
+#ifdef USE_BUFMGR_FREELIST
/*
* Try to get a buffer from the freelist. Note that the freeNext fields
* are considered to be protected by the BufFreelistLock not the
@@ -165,8 +167,9 @@ StrategyGetBuffer(BufferAccessStrategy strategy, bool *lock_held)
}
UnlockBufHdr(buf);
}
+#endif
- /* Nothing on the freelist, so run the "clock sweep" algorithm */
+ /* Run the "clock sweep" algorithm */
trycounter = NBuffers;
for (;;)
{
@@ -223,6 +229,7 @@ StrategyGetBuffer(BufferAccessStrategy strategy, bool *lock_held)
void
StrategyFreeBuffer(volatile BufferDesc *buf)
{
+#ifdef USE_BUFMGR_FREELIST
LWLockAcquire(BufFreelistLock, LW_EXCLUSIVE);
/*
@@ -238,6 +245,24 @@ StrategyFreeBuffer(volatile BufferDesc *buf)
}
LWLockRelease(BufFreelistLock);
+#endif
+}
+
+/*
+ * StrategyInitFreelist: put a buffer on the freelist during InitBufferPool
+ */
+void
+StrategyInitFreelistBuffer(volatile BufferDesc *buf)
+{
+#ifdef USE_BUFMGR_FREELIST
+ /*
+ * Initially link all the buffers together as unused. Subsequent
+ * management of this list is done by freelist.c.
+ */
+ buf->freeNext = i + 1;
+#else
+ buf->freeNext = FREENEXT_NOT_IN_LIST;
+#endif
}
/*
@@ -331,12 +356,14 @@ StrategyInitialize(bool init)
*/
Assert(init);
+#ifdef USE_BUFMGR_FREELIST
/*
* Grab the whole linked list of free buffers for our strategy. We
* assume it was previously set up by InitBufferPool().
*/
StrategyControl->firstFreeBuffer = 0;
StrategyControl->lastFreeBuffer = NBuffers - 1;
+#endif
/* Initialize the clock sweep pointer */
StrategyControl->nextVictimBuffer = 0;
diff --git a/src/include/storage/buf_internals.h b/src/include/storage/buf_internals.h
index e43719e..6a03d5d 100644
--- a/src/include/storage/buf_internals.h
+++ b/src/include/storage/buf_internals.h
@@ -190,6 +190,8 @@ extern bool StrategyRejectBuffer(BufferAccessStrategy strategy,
extern int StrategySyncStart(uint32 *complete_passes, uint32 *num_buf_alloc);
extern Size StrategyShmemSize(void);
extern void StrategyInitialize(bool init);
+extern void StrategyInitFreelistBuffer(volatile BufferDesc *buf);
+
/* buf_table.c */
extern Size BufTableShmemSize(int size);
--
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