Re: BufMgr cleanup

Your patch has been added to the PostgreSQL unapplied patches list at:

http://candle.pha.pa.us/cgi-bin/pgpatches

I will try to apply it within the next 48 hours.

---------------------------------------------------------------------------

Manfred Koizar wrote:
> Minor code cleanup in bufmgr.c and bufmgr.h, mainly by moving repeated
> lines of code into internal routines (drop_relfilenode_buffers,
> release_buffer) and by hiding unused routines (PrintBufferDescs,
> PrintPinnedBufs) behind #ifdef NOT_USED.
> Remove AbortBufferIO() declaration from bufmgr.c (already declared
> in bufmgr.h)
>
> diff -ru ../orig/src/backend/storage/buffer/bufmgr.c src/backend/storage/buffer/bufmgr.c
> --- ../orig/src/backend/storage/buffer/bufmgr.c 2002-06-13 09:32:40.000000000 +0200
> +++ src/backend/storage/buffer/bufmgr.c 2002-06-13 11:02:47.000000000 +0200
> @@ -71,7 +71,6 @@
> static void StartBufferIO(BufferDesc *buf, bool forInput);
> static void TerminateBufferIO(BufferDesc *buf);
> static void ContinueBufferIO(BufferDesc *buf, bool forInput);
> -extern void AbortBufferIO(void);
>
> /*
> * Macro : BUFFER_IS_BROKEN
> @@ -85,9 +84,14 @@
> bool *foundPtr);
> static int ReleaseBufferWithBufferLock(Buffer buffer);
> static int BufferReplace(BufferDesc *bufHdr);
> +#ifdef NOT_USED
> void PrintBufferDescs(void);
> +#endif
>
> static void write_buffer(Buffer buffer, bool unpin);
> +static void drop_relfilenode_buffers(RelFileNode rnode,
> + bool do_local, bool do_both);
> +static int release_buffer(Buffer buffer, bool havelock);
>
> /*
> * ReadBuffer -- returns a buffer containing the requested
> @@ -1097,34 +1101,26 @@
> return relation->rd_nblocks;
> }
>
> -/* ---------------------------------------------------------------------
> - * DropRelationBuffers
> - *
> - * This function removes all the buffered pages for a relation
> - * from the buffer pool. Dirty pages are simply dropped, without
> - * bothering to write them out first. This is NOT rollback-able,
> - * and so should be used only with extreme caution!
> - *
> - * We assume that the caller holds an exclusive lock on the relation,
> - * which should assure that no new buffers will be acquired for the rel
> - * meanwhile.
> +/*
> + * drop_relfilenode_buffers -- common functionality for
> + * DropRelationBuffers and
> + * DropRelFileNodeBuffers
> *
> * XXX currently it sequentially searches the buffer pool, should be
> * changed to more clever ways of searching.
> - * --------------------------------------------------------------------
> */
> -void
> -DropRelationBuffers(Relation rel)
> +static void
> +drop_relfilenode_buffers(RelFileNode rnode, bool do_local, bool do_both)
> {
> int i;
> BufferDesc *bufHdr;
>
> - if (rel->rd_myxactonly)
> + if (do_local)
> {
> for (i = 0; i < NLocBuffer; i++)
> {
> bufHdr = &LocalBufferDescriptors[i];
> - if (RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node))
> + if (RelFileNodeEquals(bufHdr->tag.rnode, rnode))
> {
> bufHdr->flags &= ~(BM_DIRTY | BM_JUST_DIRTIED);
> bufHdr->cntxDirty = false;
> @@ -1132,7 +1128,8 @@
> bufHdr->tag.rnode.relNode = InvalidOid;
> }
> }
> - return;
> + if (!do_both)
> + return;
> }
>
> LWLockAcquire(BufMgrLock, LW_EXCLUSIVE);
> @@ -1141,7 +1138,7 @@
> {
> bufHdr = &BufferDescriptors[i - 1];
> recheck:
> - if (RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node))
> + if (RelFileNodeEquals(bufHdr->tag.rnode, rnode))
> {
> /*
> * If there is I/O in progress, better wait till it's done;
> @@ -1188,6 +1185,25 @@
> }
>
> /* ---------------------------------------------------------------------
> + * DropRelationBuffers
> + *
> + * This function removes all the buffered pages for a relation
> + * from the buffer pool. Dirty pages are simply dropped, without
> + * bothering to write them out first. This is NOT rollback-able,
> + * and so should be used only with extreme caution!
> + *
> + * We assume that the caller holds an exclusive lock on the relation,
> + * which should assure that no new buffers will be acquired for the rel
> + * meanwhile.
> + * --------------------------------------------------------------------
> + */
> +void
> +DropRelationBuffers(Relation rel)
> +{
> + drop_relfilenode_buffers(rel->rd_node, rel->rd_myxactonly, false);
> +}
> +
> +/* ---------------------------------------------------------------------
> * DropRelFileNodeBuffers
> *
> * This is the same as DropRelationBuffers, except that the target
> @@ -1201,73 +1217,8 @@
> void
> DropRelFileNodeBuffers(RelFileNode rnode)
> {
> - int i;
> - BufferDesc *bufHdr;
> -
> /* We have to search both local and shared buffers... */
> -
> - for (i = 0; i < NLocBuffer; i++)
> - {
> - bufHdr = &LocalBufferDescriptors[i];
> - if (RelFileNodeEquals(bufHdr->tag.rnode, rnode))
> - {
> - bufHdr->flags &= ~(BM_DIRTY | BM_JUST_DIRTIED);
> - bufHdr->cntxDirty = false;
> - LocalRefCount[i] = 0;
> - bufHdr->tag.rnode.relNode = InvalidOid;
> - }
> - }
> -
> - LWLockAcquire(BufMgrLock, LW_EXCLUSIVE);
> -
> - for (i = 1; i <= NBuffers; i++)
> - {
> - bufHdr = &BufferDescriptors[i - 1];
> -recheck:
> - if (RelFileNodeEquals(bufHdr->tag.rnode, rnode))
> - {
> - /*
> - * If there is I/O in progress, better wait till it's done;
> - * don't want to delete the relation out from under someone
> - * who's just trying to flush the buffer!
> - */
> - if (bufHdr->flags & BM_IO_IN_PROGRESS)
> - {
> - WaitIO(bufHdr);
> -
> - /*
> - * By now, the buffer very possibly belongs to some other
> - * rel, so check again before proceeding.
> - */
> - goto recheck;
> - }
> - /* Now we can do what we came for */
> - bufHdr->flags &= ~(BM_DIRTY | BM_JUST_DIRTIED);
> - bufHdr->cntxDirty = false;
> -
> - /*
> - * Release any refcount we may have.
> - *
> - * This is very probably dead code, and if it isn't then it's
> - * probably wrong. I added the Assert to find out --- tgl
> - * 11/99.
> - */
> - if (!(bufHdr->flags & BM_FREE))
> - {
> - /* Assert checks that buffer will actually get freed! */
> - Assert(PrivateRefCount[i - 1] == 1 &&
> - bufHdr->refcount == 1);
> - ReleaseBufferWithBufferLock(i);
> - }
> -
> - /*
> - * And mark the buffer as no longer occupied by this rel.
> - */
> - BufTableDelete(bufHdr);
> - }
> - }
> -
> - LWLockRelease(BufMgrLock);
> + drop_relfilenode_buffers(rnode, true, true);
> }
>
> /* ---------------------------------------------------------------------
> @@ -1343,6 +1294,7 @@
> * use only.
> * -----------------------------------------------------------------
> */
> +#ifdef NOT_USED
> void
> PrintBufferDescs()
> {
> @@ -1375,7 +1327,9 @@
> }
> }
> }
> +#endif
>
> +#ifdef NOT_USED
> void
> PrintPinnedBufs()
> {
> @@ -1395,6 +1349,7 @@
> }
> LWLockRelease(BufMgrLock);
> }
> +#endif
>
> /*
> * BufferPoolBlowaway
> @@ -1589,14 +1544,12 @@
> return 0;
> }
>
> -#undef ReleaseBuffer
> -
> /*
> - * ReleaseBuffer -- remove the pin on a buffer without
> - * marking it dirty.
> + * release_buffer -- common functionality for
> + * ReleaseBuffer and ReleaseBufferWithBufferLock
> */
> -int
> -ReleaseBuffer(Buffer buffer)
> +static int
> +release_buffer(Buffer buffer, bool havelock)
> {
> BufferDesc *bufHdr;
>
> @@ -1617,14 +1570,30 @@
> PrivateRefCount[buffer - 1]--;
> else
> {
> - LWLockAcquire(BufMgrLock, LW_EXCLUSIVE);
> + if (!havelock)
> + LWLockAcquire(BufMgrLock, LW_EXCLUSIVE);
> +
> UnpinBuffer(bufHdr);
> - LWLockRelease(BufMgrLock);
> +
> + if (!havelock)
> + LWLockRelease(BufMgrLock);
> }
>
> return STATUS_OK;
> }
>
> +#undef ReleaseBuffer
> +
> +/*
> + * ReleaseBuffer -- remove the pin on a buffer without
> + * marking it dirty.
> + */
> +int
> +ReleaseBuffer(Buffer buffer)
> +{
> + return release_buffer(buffer, false);
> +}
> +
> /*
> * ReleaseBufferWithBufferLock
> * Same as ReleaseBuffer except we hold the bufmgr lock
> @@ -1632,27 +1601,7 @@
> static int
> ReleaseBufferWithBufferLock(Buffer buffer)
> {
> - BufferDesc *bufHdr;
> -
> - if (BufferIsLocal(buffer))
> - {
> - Assert(LocalRefCount[-buffer - 1] > 0);
> - LocalRefCount[-buffer - 1]--;
> - return STATUS_OK;
> - }
> -
> - if (BAD_BUFFER_ID(buffer))
> - return STATUS_ERROR;
> -
> - bufHdr = &BufferDescriptors[buffer - 1];
> -
> - Assert(PrivateRefCount[buffer - 1] > 0);
> - if (PrivateRefCount[buffer - 1] > 1)
> - PrivateRefCount[buffer - 1]--;
> - else
> - UnpinBuffer(bufHdr);
> -
> - return STATUS_OK;
> + return release_buffer(buffer, true);
> }
>
>
> @@ -1695,7 +1644,7 @@
> #endif
>
> #ifdef NOT_USED
> -int
> +Buffer
> ReleaseAndReadBuffer_Debug(char *file,
> int line,
> Buffer buffer,
> @@ -2117,7 +2066,7 @@
> {
> Assert(buf == InProgressBuf);
> LWLockRelease(buf->io_in_progress_lock);
> - InProgressBuf = (BufferDesc *) 0;
> + InProgressBuf = (BufferDesc *) NULL;
> }
>
> /*
> @@ -2142,7 +2091,7 @@
> void
> InitBufferIO(void)
> {
> - InProgressBuf = (BufferDesc *) 0;
> + InProgressBuf = (BufferDesc *) NULL;
> }
> #endif
>
> diff -ru ../orig/src/include/storage/bufmgr.h src/include/storage/bufmgr.h
> --- ../orig/src/include/storage/bufmgr.h 2002-06-13 09:22:59.000000000 +0200
> +++ src/include/storage/bufmgr.h 2002-06-13 10:57:22.000000000 +0200
> @@ -167,7 +167,9 @@
> extern void DropRelationBuffers(Relation rel);
> extern void DropRelFileNodeBuffers(RelFileNode rnode);
> extern void DropBuffers(Oid dbid);
> +#ifdef NOT_USED
> extern void PrintPinnedBufs(void);
> +#endif
> extern int BufferShmemSize(void);
> extern RelFileNode BufferGetFileNode(Buffer buffer);
>
>
>
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--
Bruce Momjian | http://candle.pha.pa.us
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