On Tue, Aug 30, 2022 at 03:22:43PM -0700, Nathan Bossart wrote:
> Okay, will do.
v2 attached.
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
>From df1556c6da69f8c0aae9f8878f24e21907cf4d89 Mon Sep 17 00:00:00 2001
From: Nathan Bossart <nathandboss...@gmail.com>
Date: Thu, 11 Aug 2022 16:24:26 -0700
Subject: [PATCH v2 1/1] Introduce bufmgr hooks.
These hooks can be used for maintaining a secondary buffer cache
outside of the regular shared buffers. In theory, there are many
other potential uses.
---
src/backend/storage/buffer/bufmgr.c | 35 +++++++++++++++++++++--------
src/include/storage/buf_internals.h | 14 ++++++++++++
2 files changed, 40 insertions(+), 9 deletions(-)
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index e898ffad7b..5448716a1d 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -166,6 +166,15 @@ static bool IsForInput;
/* local state for LockBufferForCleanup */
static BufferDesc *PinCountWaitBuf = NULL;
+/* hook for plugins to get control when reading in a page */
+bufmgr_read_hook_type bufmgr_read_hook = NULL;
+
+/* hook for plugins to get control when writing a page */
+bufmgr_write_hook_type bufmgr_write_hook = NULL;
+
+/* hook for plugins to get control when invalidating a page */
+bufmgr_invalidate_hook_type bufmgr_invalidate_hook = NULL;
+
/*
* Backend-Private refcount management:
*
@@ -482,7 +491,7 @@ static BufferDesc *BufferAlloc(SMgrRelation smgr,
BlockNumber blockNum,
BufferAccessStrategy strategy,
bool *foundPtr);
-static void FlushBuffer(BufferDesc *buf, SMgrRelation reln);
+static void FlushBuffer(BufferDesc *buf, SMgrRelation reln, bool for_eviction);
static void FindAndDropRelationBuffers(RelFileLocator rlocator,
ForkNumber forkNum,
BlockNumber nForkBlock,
@@ -1018,7 +1027,9 @@ ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
if (track_io_timing)
INSTR_TIME_SET_CURRENT(io_start);
- smgrread(smgr, forkNum, blockNum, (char *) bufBlock);
+ if (!bufmgr_read_hook ||
+ !(*bufmgr_read_hook) (smgr, forkNum, blockNum, (char *) bufBlock))
+ smgrread(smgr, forkNum, blockNum, (char *) bufBlock);
if (track_io_timing)
{
@@ -1269,7 +1280,7 @@ BufferAlloc(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
smgr->smgr_rlocator.locator.dbOid,
smgr->smgr_rlocator.locator.relNumber);
- FlushBuffer(buf, NULL);
+ FlushBuffer(buf, NULL, true);
LWLockRelease(BufferDescriptorGetContentLock(buf));
ScheduleBufferTagForWriteback(&BackendWritebackContext,
@@ -1544,6 +1555,9 @@ retry:
goto retry;
}
+ if (bufmgr_invalidate_hook)
+ (*bufmgr_invalidate_hook) (buf);
+
/*
* 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.
@@ -2573,7 +2587,7 @@ SyncOneBuffer(int buf_id, bool skip_recently_used, WritebackContext *wb_context)
PinBuffer_Locked(bufHdr);
LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
- FlushBuffer(bufHdr, NULL);
+ FlushBuffer(bufHdr, NULL, false);
LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
@@ -2823,7 +2837,7 @@ BufferGetTag(Buffer buffer, RelFileLocator *rlocator, ForkNumber *forknum,
* as the second parameter. If not, pass NULL.
*/
static void
-FlushBuffer(BufferDesc *buf, SMgrRelation reln)
+FlushBuffer(BufferDesc *buf, SMgrRelation reln, bool for_eviction)
{
XLogRecPtr recptr;
ErrorContextCallback errcallback;
@@ -2903,6 +2917,9 @@ FlushBuffer(BufferDesc *buf, SMgrRelation reln)
*/
bufToWrite = PageSetChecksumCopy((Page) bufBlock, buf->tag.blockNum);
+ if (bufmgr_write_hook)
+ (*bufmgr_write_hook) (reln, buf, bufToWrite, for_eviction);
+
if (track_io_timing)
INSTR_TIME_SET_CURRENT(io_start);
@@ -3589,7 +3606,7 @@ FlushRelationBuffers(Relation rel)
{
PinBuffer_Locked(bufHdr);
LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
- FlushBuffer(bufHdr, RelationGetSmgr(rel));
+ FlushBuffer(bufHdr, RelationGetSmgr(rel), false);
LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
UnpinBuffer(bufHdr, true);
}
@@ -3687,7 +3704,7 @@ FlushRelationsAllBuffers(SMgrRelation *smgrs, int nrels)
{
PinBuffer_Locked(bufHdr);
LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
- FlushBuffer(bufHdr, srelent->srel);
+ FlushBuffer(bufHdr, srelent->srel, false);
LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
UnpinBuffer(bufHdr, true);
}
@@ -3897,7 +3914,7 @@ FlushDatabaseBuffers(Oid dbid)
{
PinBuffer_Locked(bufHdr);
LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
- FlushBuffer(bufHdr, NULL);
+ FlushBuffer(bufHdr, NULL, false);
LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
UnpinBuffer(bufHdr, true);
}
@@ -3924,7 +3941,7 @@ FlushOneBuffer(Buffer buffer)
Assert(LWLockHeldByMe(BufferDescriptorGetContentLock(bufHdr)));
- FlushBuffer(bufHdr, NULL);
+ FlushBuffer(bufHdr, NULL, false);
}
/*
diff --git a/src/include/storage/buf_internals.h b/src/include/storage/buf_internals.h
index 406db6be78..ef8b683da3 100644
--- a/src/include/storage/buf_internals.h
+++ b/src/include/storage/buf_internals.h
@@ -382,6 +382,20 @@ typedef struct CkptSortItem
extern PGDLLIMPORT CkptSortItem *CkptBufferIds;
+/* hook for plugins to get control when reading in a page */
+typedef bool (*bufmgr_read_hook_type) (SMgrRelation smgr, ForkNumber forknum,
+ BlockNumber blocknum, char *buffer);
+extern PGDLLIMPORT bufmgr_read_hook_type bufmgr_read_hook;
+
+/* hook for plugins to get control when writing a page */
+typedef void (*bufmgr_write_hook_type) (SMgrRelation smgr, BufferDesc *buf,
+ char *buffer, bool for_eviction);
+extern PGDLLIMPORT bufmgr_write_hook_type bufmgr_write_hook;
+
+/* hook for plugins to get control when invalidating a page */
+typedef void (*bufmgr_invalidate_hook_type) (BufferDesc *buf);
+extern PGDLLIMPORT bufmgr_invalidate_hook_type bufmgr_invalidate_hook;
+
/*
* Internal buffer management routines
*/
--
2.25.1
