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Subject[PATCH 1/4] mm: Provide kernel parameter to allow disabling page init poisoning
From
Date
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.

In order to work around a kernel that might have CONFIG_DEBUG_VM enabled on
a system that has a large amount of memory I have added a new kernel
parameter named "page_init_poison" that can be set to "off" in order to
disable it.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
---
Documentation/admin-guide/kernel-parameters.txt | 8 ++++++++
include/linux/page-flags.h | 8 ++++++++
mm/debug.c | 16 ++++++++++++++++
mm/memblock.c | 5 ++---
mm/sparse.c | 4 +---
5 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 64a3bf54b974..7b21e0b9c394 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3047,6 +3047,14 @@
off: turn off poisoning (default)
on: turn on poisoning

+ page_init_poison= [KNL] Boot-time parameter changing the
+ state of poisoning of page structures during early
+ boot. Used to verify page metadata is not accessed
+ prior to initialization. Available with
+ CONFIG_DEBUG_VM=y.
+ off: turn off poisoning
+ on: turn on poisoning (default)
+
panic= [KNL] Kernel behaviour on panic: delay <timeout>
timeout > 0: seconds before rebooting
timeout = 0: wait forever
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 74bee8cecf4c..d00216cf00f8 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -162,6 +162,14 @@ static inline int PagePoisoned(const struct page *page)
return page->flags == PAGE_POISON_PATTERN;
}

+#ifdef CONFIG_DEBUG_VM
+void page_init_poison(struct page *page, size_t size);
+#else
+static inline void page_init_poison(struct page *page, size_t size)
+{
+}
+#endif
+
/*
* Page flags policies wrt compound pages
*
diff --git a/mm/debug.c b/mm/debug.c
index 38c926520c97..c5420422c0b5 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -175,4 +175,20 @@ void dump_mm(const struct mm_struct *mm)
);
}

+static bool page_init_poisoning __read_mostly = true;
+
+static int __init page_init_poison_param(char *buf)
+{
+ if (!buf)
+ return -EINVAL;
+ return strtobool(buf, &page_init_poisoning);
+}
+early_param("page_init_poison", page_init_poison_param);
+
+void page_init_poison(struct page *page, size_t size)
+{
+ if (page_init_poisoning)
+ memset(page, PAGE_POISON_PATTERN, size);
+}
+EXPORT_SYMBOL_GPL(page_init_poison);
#endif /* CONFIG_DEBUG_VM */
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);
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