Fine tune PTRACK_BUF_SIZE used for ptrack checkpoints.

8k of 64 bit LSNs is 64 KB, which looks like a reasonable buffer size for disk writes. On fast NVMe SSD it gives around 20% increase in ptrack checkpoint speed compared to PTRACK_BUF_SIZE == 1000, i.e. 8 KB writes. Also use proper types for writesz and PTRACK_BUF_SIZE while on it
postgrespro · Mar 31, 2021 · a8828ef · a8828ef
1 parent d16e84b
commit a8828ef
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Showing 2 changed files with 11 additions and 5 deletions.
diff --git a/engine.c b/engine.c
@@ -430,7 +430,7 @@ ptrackCheckpoint(void)
 
 		if (j == PTRACK_BUF_SIZE)
 		{
-			int			writesz = sizeof(buf); /* Up to ~2 GB for buffer size seems
+			size_t		writesz = sizeof(buf); /* Up to ~2 GB for buffer size seems
 												* to be more than enough, so never
 												* going to overflow. */
 
@@ -439,7 +439,7 @@ ptrackCheckpoint(void)
 			 * takes into account all paddings for us.
 			 */
 			ptrack_write_chunk(ptrack_tmp_fd, &crc, (char *) buf, writesz);
-			elog(DEBUG5, "ptrack checkpoint: i " UINT64_FORMAT ", j " UINT64_FORMAT ", writesz %d PtrackContentNblocks " UINT64_FORMAT,
+			elog(DEBUG5, "ptrack checkpoint: i " UINT64_FORMAT ", j " UINT64_FORMAT ", writesz %zu PtrackContentNblocks " UINT64_FORMAT,
 				 i, j, writesz, (uint64) PtrackContentNblocks);
 
 			j = 0;
@@ -449,10 +449,10 @@ ptrackCheckpoint(void)
 	/* Write if anythig left */
 	if ((i + 1) % PTRACK_BUF_SIZE != 0)
 	{
-		int			writesz = sizeof(pg_atomic_uint64) * j;
+		size_t		writesz = sizeof(pg_atomic_uint64) * j;
 
 		ptrack_write_chunk(ptrack_tmp_fd, &crc, (char *) buf, writesz);
-		elog(DEBUG5, "ptrack checkpoint: final i " UINT64_FORMAT ", j " UINT64_FORMAT ", writesz %d PtrackContentNblocks " UINT64_FORMAT,
+		elog(DEBUG5, "ptrack checkpoint: final i " UINT64_FORMAT ", j " UINT64_FORMAT ", writesz %zu PtrackContentNblocks " UINT64_FORMAT,
 			 i, j, writesz, (uint64) PtrackContentNblocks);
 	}
 

diff --git a/engine.h b/engine.h
@@ -31,7 +31,13 @@
 /* Used for atomical crash-safe update of ptrack.map */
 #define PTRACK_PATH_TMP "global/ptrack.map.tmp"
 
-#define PTRACK_BUF_SIZE 1000
+/*
+ * 8k of 64 bit LSNs is 64 KB, which looks like a reasonable
+ * buffer size for disk writes.  On fast NVMe SSD it gives
+ * around 20% increase in ptrack checkpoint speed compared
+ * to PTRACK_BUF_SIZE == 1000, i.e. 8 KB writes.
+ */
+#define PTRACK_BUF_SIZE ((uint64) 8000)
 
 /* Ptrack magic bytes */
 #define PTRACK_MAGIC "ptk"