alloc_tag: skip pgalloc_tag_swap if profiling is disabled

When memory allocation profiling is disabled, there is no need to swap
allocation tags during migration.  Skip it to avoid unnecessary overhead.

Once I added these checks, the overhead of the mode when memory profiling
is enabled but turned off went down by about 50%.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: e0a955b ("mm/codetag: add pgalloc_tag_copy()")
Signed-off-by: Suren Baghdasaryan <[email protected]>
Cc: David Wang <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: Yu Zhao <[email protected]>
Cc: Zhenhua Huang <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: surenbaghdasaryan

lib/alloc_tag.c

@@ -195,6 +195,9 @@ void pgalloc_tag_swap(struct folio *new, struct folio *old)
 	union codetag_ref ref_old, ref_new;
 	struct alloc_tag *tag_old, *tag_new;
 
+	if (!mem_alloc_profiling_enabled())
+		return;
+
 	tag_old = pgalloc_tag_get(&old->page);
 	if (!tag_old)
 		return;