From fad1f23c20e5bd0eb73cb8e124f063ac95cb307d Mon Sep 17 00:00:00 2001
From: Kevin Grittner <Kevin.Grittner@wicourts.gov>
Date: Sat, 24 Dec 2011 13:07:13 -0600
Subject: [PATCH] WIP on background hinting.

---
 src/backend/storage/buffer/bufmgr.c | 48 ++++++++++++++++++++++++++++-
 src/include/storage/bufmgr.h        |  1 +
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index bc9c2da427..46daa3c471 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -49,6 +49,10 @@
 #include "utils/resowner.h"
 #include "utils/timestamp.h"
 
+/* Is the buffer in a suitable state for backgroun hinting? */
+#define BufferNeedsHinting(bufHdr) (((BM_DIRTY | BM_VALID | BM_TAG_VALID | BM_IO_IN_PROGRESS) \
+  & ((bufHdr)->flags)) \
+  == (BM_DIRTY | BM_VALID | BM_TAG_VALID))
 
 /* Note: these two macros only work on shared buffers, not local ones! */
 #define BufHdrGetBlock(bufHdr)	((Block) (BufferBlocks + ((Size) (bufHdr)->buf_id) * BLCKSZ))
@@ -1304,12 +1308,54 @@ BufferSync(int flags)
 }
 
 /*
- * BgHintBuffers -- hint any dirty buffers that are ripe for it
+ * BgHintBuffers -- Hint any dirty buffers that are ripe for it.
  *
  * TODO: Fill this in.
  */
 void
 BgHintBuffers(void)
+{
+	int			buf_id;
+
+	/* Make sure we can handle the pin inside HintOneBuffer */
+	ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
+
+	for (buf_id = 0; buf_id < NBuffers; buf_id++)
+	{
+		volatile BufferDesc *bufHdr = &BufferDescriptors[buf_id];
+
+		/* TODO: Is anything special needed here regarding local buffers? */
+
+		if (!BufferNeedsHinting(bufHdr))
+			continue;
+
+		if (!PinBuffer(bufHdr))
+		{
+			/* Buffer was not valid on pin; move on with minimum work. */
+			UnpinBuffer(bufHdr, true);
+			continue;
+		}
+
+		if (BufferNeedsHinting(bufHdr))
+		{
+			LWLockAcquire(bufHdr->content_lock, LW_SHARED);
+			HintOneBuffer(BufferDescriptorGetBuffer(bufHdr));
+			LWLockRelease(bufHdr->content_lock);
+		}
+
+		UnpinBuffer(bufHdr, true);
+	}
+}
+
+/*
+ * BgHintBuffers -- Set hint bits where possible for a pinned and locked buffer.
+ *
+ * Buffer must be pinned and content-locked by caller.
+ *
+ * TODO: Fill this in.
+ */
+void
+HintOneBuffer(Buffer buffer)
 {
 	
 }
diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h
index ee52cbf4fd..fc3c0b177d 100644
--- a/src/include/storage/bufmgr.h
+++ b/src/include/storage/bufmgr.h
@@ -216,6 +216,7 @@ extern void BufmgrCommit(void);
 extern void BgBufferSync(void);
 
 extern void BgHintBuffers(void);
+extern void HintOneBuffer(Buffer buffer);
 
 extern void AtProcExit_LocalBuffers(void);
 
-- 
2.39.5