Avoid function call overhead of pg_popcount() in syslogger.c.

nathan-bossart · nathan-bossart · commit 4133c1f45c54 · 2024-04-02T10:32:49.000-05:00
Instead of calling the pg_popcount() function for a single byte, we can look up the value in the pg_number_of_ones array. Discussion: https://postgr.es/m/20240401221117.GB2362108%40nathanxps13
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
@@ -898,7 +898,7 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 		if (p.nuls[0] == '\0' && p.nuls[1] == '\0' &&
 			p.len > 0 && p.len <= PIPE_MAX_PAYLOAD &&
 			p.pid != 0 &&
-			pg_popcount((char *) &dest_flags, 1) == 1)
+			pg_number_of_ones[dest_flags] == 1)
 		{
 			List	   *buffer_list;
 			ListCell   *cell;

Original file line number	Diff line number	Diff line change
`@@ -898,7 +898,7 @@ process_pipe_input(char logbuffer, int bytes_in_logbuffer)`
`898`	`898`	`if (p.nuls[0] == '\0' && p.nuls[1] == '\0' &&`
`899`	`899`	`p.len > 0 && p.len <= PIPE_MAX_PAYLOAD &&`
`900`	`900`	`p.pid != 0 &&`
`901`		`- pg_popcount((char *) &dest_flags, 1) == 1)`
	`901`	`+ pg_number_of_ones[dest_flags] == 1)`
`902`	`902`	`{`
`903`	`903`	`List *buffer_list;`
`904`	`904`	`ListCell *cell;`