2 files changed, 21 insertions, 3 deletions

diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index 957d3da53ddd..a0c136af9c91 100644
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -16,8 +16,8 @@ config DEBUG_PAGEALLOC
         select PAGE_POISONING if !ARCH_SUPPORTS_DEBUG_PAGEALLOC
         ---help---
           Unmap pages from the kernel linear mapping after free_pages().
-          This results in a large slowdown, but helps to find certain types
-          of memory corruption.
+          Depending on runtime enablement, this results in a small or large
+          slowdown, but helps to find certain types of memory corruption.
 
           For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC,
           fill the pages with poison patterns after free_pages() and verify
@@ -26,5 +26,19 @@ config DEBUG_PAGEALLOC
           that would result in incorrect warnings of memory corruption after
           a resume because free pages are not saved to the suspend image.
 
+          By default this option will have a small overhead, e.g. by not
+          allowing the kernel mapping to be backed by large pages on some
+          architectures. Even bigger overhead comes when the debugging is
+          enabled by DEBUG_PAGEALLOC_ENABLE_DEFAULT or the debug_pagealloc
+          command line parameter.
+
+config DEBUG_PAGEALLOC_ENABLE_DEFAULT
+        bool "Enable debug page memory allocations by default?"
+        default n
+        depends on DEBUG_PAGEALLOC
+        ---help---
+          Enable debug page memory allocations by default? This value
+          can be overridden by debug_pagealloc=off|on.
+
 config PAGE_POISONING
         bool
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index fe4378fc0ab6..36a0a792f4f8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -478,7 +478,8 @@ void prep_compound_page(struct page *page, unsigned int order)
 
 #ifdef CONFIG_DEBUG_PAGEALLOC
 unsigned int _debug_guardpage_minorder;
-bool _debug_pagealloc_enabled __read_mostly;
+bool _debug_pagealloc_enabled __read_mostly
+                        = IS_ENABLED(CONFIG_DEBUG_PAGEALLOC_ENABLE_DEFAULT);
 bool _debug_guardpage_enabled __read_mostly;
 
 static int __init early_debug_pagealloc(char *buf)
@@ -489,6 +490,9 @@ static int __init early_debug_pagealloc(char *buf)
         if (strcmp(buf, "on") == 0)
                 _debug_pagealloc_enabled = true;
 
+        if (strcmp(buf, "off") == 0)
+                _debug_pagealloc_enabled = false;
+
         return 0;
 }
 early_param("debug_pagealloc", early_debug_pagealloc);