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

[Pasha Tatashin <Pavel.Tatashin@microsoft.com>]

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);
>