Horton

RE: Improve eviction algorithm in ReorderBuffer

Hayato Kuroda (Fujitsu) <kuroda.hayato@fujitsu.com>

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From: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
To: 'Heikki Linnakangas' <hlinnaka@iki.fi>, Masahiko Sawada <sawada.mshk@gmail.com>
Cc: Michael Paquier <michael@paquier.xyz>, Jeff Davis <pgsql@j-davis.com>, vignesh C <vignesh21@gmail.com>, Peter Smith <smithpb2250@gmail.com>, Tomas Vondra <tomas.vondra@enterprisedb.com>, Shubham Khanna <khannashubham1197@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Amit Kapila <amit.kapila16@gmail.com>
Date: 2024-04-11T01:46:37Z
Lists: pgsql-hackers

Attachments

Dear Heikki,

I also prototyped the idea, which has almost the same shape.
I attached just in case, but we may not have to see.

Few comments based on the experiment.

```
+	/* txn_heap is ordered by transaction size */
+	buffer->txn_heap = pairingheap_allocate(ReorderBufferTXNSizeCompare, NULL);
```

I think the pairing heap should be in the same MemoryContext with the buffer.
Can we add MemoryContextSwithTo()?

```
+		/* Update the max-heap */
+		if (oldsize != 0)
+			pairingheap_remove(rb->txn_heap, &txn->txn_node);
+		pairingheap_add(rb->txn_heap, &txn->txn_node);
...
+		/* Update the max-heap */
+		pairingheap_remove(rb->txn_heap, &txn->txn_node);
+		if (txn->size != 0)
+			pairingheap_add(rb->txn_heap, &txn->txn_node);
```

Since the number of stored transactions does not affect to the insert operation, we may able
to add the node while creating ReorederBufferTXN and remove while cleaning up it. This can
reduce branches in ReorderBufferChangeMemoryUpdate().

Best Regards,
Hayato Kuroda
FUJITSU LIMITED
https://www.fujitsu.com/

Commits

  1. Revert indexed and enlargable binary heap implementation.

  2. Replace binaryheap + index with pairingheap in reorderbuffer.c

  3. Improve eviction algorithm in ReorderBuffer using max-heap for many subtransactions.

  4. Add functions to binaryheap for efficient key removal and update.

  5. Make binaryheap enlargeable.