Speedup and increase usability of set proc title functions

The setting of the process title could be seen on profiles of very
fast-to-execute queries.  In many locations where we call
set_ps_display() we pass along a string constant, the length of which is
known during compilation.  Here we effectively rename set_ps_display() to
set_ps_display_with_len() and then add a static inline function named
set_ps_display() which calls strlen() on the given string.  This allows
the compiler to optimize away the strlen() call when dealing with
call sites passing a string constant.  We can then also use memcpy()
instead of strlcpy() to copy the string into the destination buffer.
That's significantly faster than strlcpy's byte-at-a-time way of
copying.

Here we also take measures to improve some code which was adjusting the
process title to add a " waiting" suffix to it.  Call sites which require
this can now just call set_ps_display_suffix() to add or adjust the suffix
and call set_ps_display_remove_suffix() to remove it again.

Reviewed-by: Andres Freund
Discussion: https://postgr.es/m/CAApHDvocBvvk-0gWNA2Gohe+sv9fMcv+fK_G+siBKJrgDG4O7g@mail.gmail.com

1 files changed, 9 insertions, 16 deletions

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 2d6dbc65612..98904a7c05a 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -4302,8 +4302,8 @@ void
 LockBufferForCleanup(Buffer buffer)
 {
 	BufferDesc *bufHdr;
-	char	   *new_status = NULL;
 	TimestampTz waitStart = 0;
+	bool		waiting = false;
 	bool		logged_recovery_conflict = false;
 
 	Assert(BufferIsPinned(buffer));
@@ -4350,11 +4350,11 @@ LockBufferForCleanup(Buffer buffer)
 									waitStart, GetCurrentTimestamp(),
 									NULL, false);
 
-			/* Report change to non-waiting status */
-			if (new_status)
+			if (waiting)
 			{
-				set_ps_display(new_status);
-				pfree(new_status);
+				/* reset ps display to remove the suffix if we added one */
+				set_ps_display_remove_suffix();
+				waiting = false;
 			}
 			return;
 		}
@@ -4374,18 +4374,11 @@ LockBufferForCleanup(Buffer buffer)
 		/* Wait to be signaled by UnpinBuffer() */
 		if (InHotStandby)
 		{
-			/* Report change to waiting status */
-			if (update_process_title && new_status == NULL)
+			if (!waiting)
 			{
-				const char *old_status;
-				int			len;
-
-				old_status = get_ps_display(&len);
-				new_status = (char *) palloc(len + 8 + 1);
-				memcpy(new_status, old_status, len);
-				strcpy(new_status + len, " waiting");
-				set_ps_display(new_status);
-				new_status[len] = '\0'; /* truncate off " waiting" */
+				/* adjust the process title to indicate that it's waiting */
+				set_ps_display_suffix("waiting");
+				waiting = true;
 			}
 
 			/*