linux-kernel - [PATCH v2 1/2] mm: Move page struct poisoning to CONFIG_DEBUG_VM_PAGE_INIT

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Date:   Wed, 05 Sep 2018 14:13:28 -0700
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     alexander.h.duyck@...el.com, pavel.tatashin@...rosoft.com,
        mhocko@...e.com, dave.hansen@...el.com, akpm@...ux-foundation.org,
        mingo@...nel.org, kirill.shutemov@...ux.intel.com
Subject: [PATCH v2 1/2] mm: Move page struct poisoning to
 CONFIG_DEBUG_VM_PAGE_INIT_POISON

From: Alexander Duyck <alexander.h.duyck@...el.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@...el.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);