Function BufferSync

src/backend/storage/buffer/bufmgr.c:2059–2326

* BufferSync -- Write out all dirty buffers in the pool. * * This is called at checkpoint time to write out all dirty shared buffers. * The checkpoint request flags should be passed in. If CHECKPOINT_IMMEDIATE * is set, we disable delays between writes; if CHECKPOINT_IS_SHUTDOWN, * CHECKPOINT_END_OF_RECOVERY or CHECKPOINT_FLUSH_ALL is set, we write even * unlogged buffers, which are otherwi

 * currently have no effect here.
 */
static void
BufferSync(int flags)
{
	uint32		buf_state;
	int			buf_id;
	int			num_to_scan;
	int			num_spaces;
	int			num_processed;
	int			num_written;
	CkptTsStatus *per_ts_stat = NULL;
	Oid			last_tsid;
	binaryheap *ts_heap;
	int			i;
	int			mask = BM_DIRTY;
	WritebackContext wb_context;

	/* Make sure we can handle the pin inside SyncOneBuffer */
	ResourceOwnerEnlargeBuffers(CurrentResourceOwner);

	/*
	 * Unless this is a shutdown checkpoint or we have been explicitly told,
	 * we write only permanent, dirty buffers.  But at shutdown or end of
	 * recovery, we write all dirty buffers.
	 */
	if (!((flags & (CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_END_OF_RECOVERY |
					CHECKPOINT_FLUSH_ALL))))
		mask |= BM_PERMANENT;

	/*
	 * Loop over all buffers, and mark the ones that need to be written with
	 * BM_CHECKPOINT_NEEDED.  Count them as we go (num_to_scan), so that we
	 * can estimate how much work needs to be done.
	 *
	 * This allows us to write only those pages that were dirty when the
	 * checkpoint began, and not those that get dirtied while it proceeds.
	 * Whenever a page with BM_CHECKPOINT_NEEDED is written out, either by us
	 * later in this function, or by normal backends or the bgwriter cleaning
	 * scan, the flag is cleared.  Any buffer dirtied after this point won't
	 * have the flag set.
	 *
	 * Note that if we fail to write some buffer, we may leave buffers with
	 * BM_CHECKPOINT_NEEDED still set.  This is OK since any such buffer would
	 * certainly need to be written for the next checkpoint attempt, too.
	 */
	num_to_scan = 0;
	for (buf_id = 0; buf_id < NBuffers; buf_id++)
	{
		BufferDesc *bufHdr = GetBufferDescriptor(buf_id);

		/*
		 * Header spinlock is enough to examine BM_DIRTY, see comment in
		 * SyncOneBuffer.
		 */
		buf_state = LockBufHdr(bufHdr);

		/*
		 * Temp tables in Cloudberry use shared buffers.  Filter buffers
		 * belonging to temp tables out during checkpoint.