mm/swapfile.c: put_swap_page: share more between huge/normal code path

yhuang-intel · torvalds · commit c2343d2761f8 · 2018-08-22T10:52:44.000-07:00
In this patch, locking related code is shared between huge/normal code path in put_swap_page() to reduce code duplication. The `free_entries == 0` case is merged into the more general `free_entries != SWAPFILE_CLUSTER` case, because the new locking method makes it easy. The added lines is same as the removed lines. But the code size is increased when CONFIG_TRANSPARENT_HUGEPAGE=n. text data bss dec hex filename base: 24123 2004 340 26467 6763 mm/swapfile.o unified: 24485 2004 340 26829 68cd mm/swapfile.o Dig on step deeper with `size -A mm/swapfile.o` for base and unified kernel and compare the result, yields, -.text 17723 0 +.text 17835 0 -.orc_unwind_ip 1380 0 +.orc_unwind_ip 1480 0 -.orc_unwind 2070 0 +.orc_unwind 2220 0 -Total 26686 +Total 27048 The total difference is the same. The text segment difference is much smaller: 112. More difference comes from the ORC unwinder segments: (1480 + 2220) - (1380 + 2070) = 250. If the frame pointer unwinder is used, this costs nothing. Link: http://lkml.kernel.org/r/20180720071845.17920-9-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com> Acked-by: Dave Hansen <dave.hansen@linux.intel.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Shaohua Li <shli@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Matthew Wilcox <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/swapfile.c b/mm/swapfile.c
@@ -1223,8 +1223,8 @@ void put_swap_page(struct page *page, swp_entry_t entry)
 	if (!si)
 		return;
 
+	ci = lock_cluster_or_swap_info(si, offset);
 	if (size == SWAPFILE_CLUSTER) {
-		ci = lock_cluster(si, offset);
 		VM_BUG_ON(!cluster_is_huge(ci));
 		map = si->swap_map + offset;
 		for (i = 0; i < SWAPFILE_CLUSTER; i++) {
@@ -1233,13 +1233,9 @@ void put_swap_page(struct page *page, swp_entry_t entry)
 			if (val == SWAP_HAS_CACHE)
 				free_entries++;
 		}
-		if (!free_entries) {
-			for (i = 0; i < SWAPFILE_CLUSTER; i++)
-				map[i] &= ~SWAP_HAS_CACHE;
-		}
 		cluster_clear_huge(ci);
-		unlock_cluster(ci);
 		if (free_entries == SWAPFILE_CLUSTER) {
+			unlock_cluster_or_swap_info(si, ci);
 			spin_lock(&si->lock);
 			ci = lock_cluster(si, offset);
 			memset(map, 0, SWAPFILE_CLUSTER);
@@ -1250,12 +1246,16 @@ void put_swap_page(struct page *page, swp_entry_t entry)
 			return;
 		}
 	}
-	if (size == 1 || free_entries) {
-		for (i = 0; i < size; i++, entry.val++) {
-			if (!__swap_entry_free(si, entry, SWAP_HAS_CACHE))
-				free_swap_slot(entry);
+	for (i = 0; i < size; i++, entry.val++) {
+		if (!__swap_entry_free_locked(si, offset + i, SWAP_HAS_CACHE)) {
+			unlock_cluster_or_swap_info(si, ci);
+			free_swap_slot(entry);
+			if (i == size - 1)
+				return;
+			lock_cluster_or_swap_info(si, offset);
 		}
 	}
+	unlock_cluster_or_swap_info(si, ci);
 }
 
 #ifdef CONFIG_THP_SWAP
