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


On 9/10/18 7:43 PM, Alexander Duyck wrote:
> 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>

Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com>

Thank you,
Pavel

> ---
> 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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