[PATCH v2 1/2] mm: Move page struct poisoning to CONFIG_DEBUG_VM_PAGE_INIT_POISON

Alexander Duyck
2018-09-05T21:13:32Z

From: Alexander Duyck <alexander.h.duyck@intel.com>

On systems with a large amount of memory it can take a significant amount
of time to initialize all of the page structs with the PAGE_POISON_PATTERN
value. I have seen it take over 2 minutes to initialize a system with
over 12GB of RAM.

In order to work around the issue I had to disable CONFIG_DEBUG_VM and then
the boot time returned to something much more reasonable as the
arch_add_memory call completed in milliseconds versus seconds. However in
doing that I had to disable all of the other VM debugging on the system.

Instead of keeping the value in CONFIG_DEBUG_VM I am adding a new CONFIG
value called CONFIG_DEBUG_VM_PAGE_INIT_POISON that will control the page
poisoning independent of the CONFIG_DEBUG_VM option.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
---
include/linux/page-flags.h | 8 ++++++++
lib/Kconfig.debug | 14 ++++++++++++++
mm/memblock.c | 5 ++---
mm/sparse.c | 4 +---
4 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 74bee8cecf4c..0e95ca63375a 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -13,6 +13,7 @@
#include <linux/mm_types.h>
#include <generated/bounds.h>
#endif /* !__GENERATING_BOUNDS_H */
+#include <linux/string.h>

/*
* Various page->flags bits:
@@ -162,6 +163,13 @@ static inline int PagePoisoned(const struct page *page)
return page->flags == PAGE_POISON_PATTERN;
}

+static inline void page_init_poison(struct page *page, size_t size)
+{
+#ifdef CONFIG_DEBUG_VM_PAGE_INIT_POISON
+ memset(page, PAGE_POISON_PATTERN, size);
+#endif
+}
+
/*
* Page flags policies wrt compound pages
*
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 613316724c6a..3b1277c52fed 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -637,6 +637,20 @@ config DEBUG_VM_PGFLAGS

If unsure, say N.

+config DEBUG_VM_PAGE_INIT_POISON
+ bool "Enable early page metadata poisoning"
+ default y
+ depends on DEBUG_VM
+ help
+ Seed the page metadata with a poison pattern to improve the
+ likelihood of detecting attempts to access the page prior to
+ initialization by the memory subsystem.
+
+ This initialization can result in a longer boot time for systems
+ with a large amount of memory.
+
+ If unsure, say Y.
+
config ARCH_HAS_DEBUG_VIRTUAL
bool

diff --git a/mm/memblock.c b/mm/memblock.c
index 237944479d25..a85315083b5a 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1444,10 +1444,9 @@ void * __init memblock_virt_alloc_try_nid_raw(

ptr = memblock_virt_alloc_internal(size, align,
min_addr, max_addr, nid);
-#ifdef CONFIG_DEBUG_VM
if (ptr && size > 0)
- memset(ptr, PAGE_POISON_PATTERN, size);
-#endif
+ page_init_poison(ptr, size);
+
return ptr;
}

diff --git a/mm/sparse.c b/mm/sparse.c
index 10b07eea9a6e..67ad061f7fb8 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -696,13 +696,11 @@ int __meminit sparse_add_one_section(struct pglist_data *pgdat,
goto out;
}

-#ifdef CONFIG_DEBUG_VM
/*
* Poison uninitialized struct pages in order to catch invalid flags
* combinations.
*/
- memset(memmap, PAGE_POISON_PATTERN, sizeof(struct page) * PAGES_PER_SECTION);
-#endif
+ page_init_poison(memmap, sizeof(struct page) * PAGES_PER_SECTION);

section_mark_present(ms);
sparse_init_one_section(ms, section_nr, memmap, usemap);