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Date:	Thu, 04 Apr 2013 08:17:08 +0800
From:	Simon Jeons <simon.jeons@...il.com>
To:	Cliff Wickman <cpw@....com>
CC:	linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
	wli@...omorphy.com
Subject: Re: [PATCH] mm, x86: no zeroing of hugetlbfs pages at boot

On 03/07/2013 05:50 AM, Cliff Wickman wrote:
> From: Cliff Wickman <cpw@....com>
>
> Allocating a large number of 1GB hugetlbfs pages at boot takes a
> very long time.
>
> Large system sites would at times like to allocate a very large amount of
> memory as 1GB pages.  They would put this on the kernel boot line:
>     default_hugepagesz=1G hugepagesz=1G hugepages=4096
> [Dynamic allocation of 1G pages is not an option, as zone pages only go
>   up to MAX_ORDER, and MAX_ORDER cannot exceed the section size.]
>
> Each page is zeroed as it is allocated, and all allocation is done by
> cpu 0, as this path is early in boot:

How you confirm they are done by cpu 0? just cpu 0 works during boot?

>        start_kernel
>          kernel_init
>            do_pre_smp_initcalls
>              hugetlb_init
>                hugetlb_init_hstates
>                  hugetlb_hstate_alloc_pages
>
> Zeroing remote (offnode) memory takes ~1GB/sec (and most memory is offnode
> on large numa systems).
> This estimate is approximate (it depends on core frequency & number of hops
> to remote memory) but should be within a factor of 2 on most systems.
> A benchmark attempting to reserve a TB for 1GB pages would thus require
> ~1000 seconds of boot time just for this allocating.  32TB would take 8 hours.
>
> I propose passing a flag to the early allocator to indicate that no zeroing
> of a page should be done.  The 'no zeroing' flag would have to be passed
> down this code path:
>
>    hugetlb_hstate_alloc_pages
>      alloc_bootmem_huge_page
>        __alloc_bootmem_node_nopanic NO_ZERO  (nobootmem.c)
>          __alloc_memory_core_early  NO_ZERO
> 	  if (!(flags & NO_ZERO))
>              memset(ptr, 0, size);
>
> Or this path if CONFIG_NO_BOOTMEM is not set:
>
>    hugetlb_hstate_alloc_pages
>      alloc_bootmem_huge_page
>        __alloc_bootmem_node_nopanic  NO_ZERO  (bootmem.c)
>          alloc_bootmem_core          NO_ZERO
> 	  if (!(flags & NO_ZERO))
>              memset(region, 0, size);
>          __alloc_bootmem_nopanic     NO_ZERO
>            ___alloc_bootmem_nopanic  NO_ZERO
>              alloc_bootmem_core      NO_ZERO
> 	      if (!(flags & NO_ZERO))
>                  memset(region, 0, size);
>
> Signed-off-by: Cliff Wickman <cpw@....com>
>
> ---
>   arch/x86/kernel/setup_percpu.c |    4 ++--
>   include/linux/bootmem.h        |   23 ++++++++++++++++-------
>   mm/bootmem.c                   |   12 +++++++-----
>   mm/hugetlb.c                   |    3 ++-
>   mm/nobootmem.c                 |   41 +++++++++++++++++++++++------------------
>   mm/page_cgroup.c               |    2 +-
>   mm/sparse.c                    |    2 +-
>   7 files changed, 52 insertions(+), 35 deletions(-)
>
> Index: linux/include/linux/bootmem.h
> ===================================================================
> --- linux.orig/include/linux/bootmem.h
> +++ linux/include/linux/bootmem.h
> @@ -8,6 +8,11 @@
>   #include <asm/dma.h>
>   
>   /*
> + * allocation flags
> + */
> +#define NO_ZERO		0x00000001
> +
> +/*
>    *  simple boot-time physical memory area allocator.
>    */
>   
> @@ -79,7 +84,8 @@ extern void *__alloc_bootmem(unsigned lo
>   			     unsigned long goal);
>   extern void *__alloc_bootmem_nopanic(unsigned long size,
>   				     unsigned long align,
> -				     unsigned long goal);
> +				     unsigned long goal,
> +				     u32 flags);
>   extern void *__alloc_bootmem_node(pg_data_t *pgdat,
>   				  unsigned long size,
>   				  unsigned long align,
> @@ -91,12 +97,14 @@ void *__alloc_bootmem_node_high(pg_data_
>   extern void *__alloc_bootmem_node_nopanic(pg_data_t *pgdat,
>   				  unsigned long size,
>   				  unsigned long align,
> -				  unsigned long goal);
> +				  unsigned long goal,
> +				  u32 flags);
>   void *___alloc_bootmem_node_nopanic(pg_data_t *pgdat,
>   				  unsigned long size,
>   				  unsigned long align,
>   				  unsigned long goal,
> -				  unsigned long limit);
> +				  unsigned long limit,
> +				  u32 flags);
>   extern void *__alloc_bootmem_low(unsigned long size,
>   				 unsigned long align,
>   				 unsigned long goal);
> @@ -120,19 +128,20 @@ extern void *__alloc_bootmem_low_node(pg
>   #define alloc_bootmem_align(x, align) \
>   	__alloc_bootmem(x, align, BOOTMEM_LOW_LIMIT)
>   #define alloc_bootmem_nopanic(x) \
> -	__alloc_bootmem_nopanic(x, SMP_CACHE_BYTES, BOOTMEM_LOW_LIMIT)
> +	__alloc_bootmem_nopanic(x, SMP_CACHE_BYTES, BOOTMEM_LOW_LIMIT, 0)
>   #define alloc_bootmem_pages(x) \
>   	__alloc_bootmem(x, PAGE_SIZE, BOOTMEM_LOW_LIMIT)
>   #define alloc_bootmem_pages_nopanic(x) \
> -	__alloc_bootmem_nopanic(x, PAGE_SIZE, BOOTMEM_LOW_LIMIT)
> +	__alloc_bootmem_nopanic(x, PAGE_SIZE, BOOTMEM_LOW_LIMIT, 0)
>   #define alloc_bootmem_node(pgdat, x) \
>   	__alloc_bootmem_node(pgdat, x, SMP_CACHE_BYTES, BOOTMEM_LOW_LIMIT)
>   #define alloc_bootmem_node_nopanic(pgdat, x) \
> -	__alloc_bootmem_node_nopanic(pgdat, x, SMP_CACHE_BYTES, BOOTMEM_LOW_LIMIT)
> +	__alloc_bootmem_node_nopanic(pgdat, x, SMP_CACHE_BYTES, \
> +				     BOOTMEM_LOW_LIMIT, 0)
>   #define alloc_bootmem_pages_node(pgdat, x) \
>   	__alloc_bootmem_node(pgdat, x, PAGE_SIZE, BOOTMEM_LOW_LIMIT)
>   #define alloc_bootmem_pages_node_nopanic(pgdat, x) \
> -	__alloc_bootmem_node_nopanic(pgdat, x, PAGE_SIZE, BOOTMEM_LOW_LIMIT)
> +	__alloc_bootmem_node_nopanic(pgdat, x, PAGE_SIZE, BOOTMEM_LOW_LIMIT, 0)
>   
>   #define alloc_bootmem_low(x) \
>   	__alloc_bootmem_low(x, SMP_CACHE_BYTES, 0)
> Index: linux/arch/x86/kernel/setup_percpu.c
> ===================================================================
> --- linux.orig/arch/x86/kernel/setup_percpu.c
> +++ linux/arch/x86/kernel/setup_percpu.c
> @@ -104,14 +104,14 @@ static void * __init pcpu_alloc_bootmem(
>   	void *ptr;
>   
>   	if (!node_online(node) || !NODE_DATA(node)) {
> -		ptr = __alloc_bootmem_nopanic(size, align, goal);
> +		ptr = __alloc_bootmem_nopanic(size, align, goal, 0);
>   		pr_info("cpu %d has no node %d or node-local memory\n",
>   			cpu, node);
>   		pr_debug("per cpu data for cpu%d %lu bytes at %016lx\n",
>   			 cpu, size, __pa(ptr));
>   	} else {
>   		ptr = __alloc_bootmem_node_nopanic(NODE_DATA(node),
> -						   size, align, goal);
> +						   size, align, goal, 0);
>   		pr_debug("per cpu data for cpu%d %lu bytes on node%d at %016lx\n",
>   			 cpu, size, node, __pa(ptr));
>   	}
> Index: linux/mm/nobootmem.c
> ===================================================================
> --- linux.orig/mm/nobootmem.c
> +++ linux/mm/nobootmem.c
> @@ -33,7 +33,7 @@ unsigned long min_low_pfn;
>   unsigned long max_pfn;
>   
>   static void * __init __alloc_memory_core_early(int nid, u64 size, u64 align,
> -					u64 goal, u64 limit)
> +					u64 goal, u64 limit, u32 flags)
>   {
>   	void *ptr;
>   	u64 addr;
> @@ -46,7 +46,8 @@ static void * __init __alloc_memory_core
>   		return NULL;
>   
>   	ptr = phys_to_virt(addr);
> -	memset(ptr, 0, size);
> +	if (!(flags & NO_ZERO))
> +		memset(ptr, 0, size);
>   	memblock_reserve(addr, size);
>   	/*
>   	 * The min_count is set to 0 so that bootmem allocated blocks
> @@ -208,7 +209,8 @@ void __init free_bootmem(unsigned long a
>   static void * __init ___alloc_bootmem_nopanic(unsigned long size,
>   					unsigned long align,
>   					unsigned long goal,
> -					unsigned long limit)
> +					unsigned long limit,
> +					u32 flags)
>   {
>   	void *ptr;
>   
> @@ -217,7 +219,8 @@ static void * __init ___alloc_bootmem_no
>   
>   restart:
>   
> -	ptr = __alloc_memory_core_early(MAX_NUMNODES, size, align, goal, limit);
> +	ptr = __alloc_memory_core_early(MAX_NUMNODES, size, align, goal,
> +					limit, 0);
>   
>   	if (ptr)
>   		return ptr;
> @@ -244,17 +247,17 @@ restart:
>    * Returns NULL on failure.
>    */
>   void * __init __alloc_bootmem_nopanic(unsigned long size, unsigned long align,
> -					unsigned long goal)
> +					unsigned long goal, u32 flags)
>   {
>   	unsigned long limit = -1UL;
>   
> -	return ___alloc_bootmem_nopanic(size, align, goal, limit);
> +	return ___alloc_bootmem_nopanic(size, align, goal, limit, flags);
>   }
>   
>   static void * __init ___alloc_bootmem(unsigned long size, unsigned long align,
> -					unsigned long goal, unsigned long limit)
> +			unsigned long goal, unsigned long limit, u32 flags)
>   {
> -	void *mem = ___alloc_bootmem_nopanic(size, align, goal, limit);
> +	void *mem = ___alloc_bootmem_nopanic(size, align, goal, limit, flags);
>   
>   	if (mem)
>   		return mem;
> @@ -284,25 +287,26 @@ void * __init __alloc_bootmem(unsigned l
>   {
>   	unsigned long limit = -1UL;
>   
> -	return ___alloc_bootmem(size, align, goal, limit);
> +	return ___alloc_bootmem(size, align, goal, limit, 0);
>   }
>   
>   void * __init ___alloc_bootmem_node_nopanic(pg_data_t *pgdat,
>   						   unsigned long size,
>   						   unsigned long align,
>   						   unsigned long goal,
> -						   unsigned long limit)
> +						   unsigned long limit,
> +						   u32 flags)
>   {
>   	void *ptr;
>   
>   again:
>   	ptr = __alloc_memory_core_early(pgdat->node_id, size, align,
> -					goal, limit);
> +					goal, limit, flags);
>   	if (ptr)
>   		return ptr;
>   
>   	ptr = __alloc_memory_core_early(MAX_NUMNODES, size, align,
> -					goal, limit);
> +					goal, limit, flags);
>   	if (ptr)
>   		return ptr;
>   
> @@ -315,12 +319,13 @@ again:
>   }
>   
>   void * __init __alloc_bootmem_node_nopanic(pg_data_t *pgdat, unsigned long size,
> -				   unsigned long align, unsigned long goal)
> +			unsigned long align, unsigned long goal, u32 flags)
>   {
>   	if (WARN_ON_ONCE(slab_is_available()))
>   		return kzalloc_node(size, GFP_NOWAIT, pgdat->node_id);
>   
> -	return ___alloc_bootmem_node_nopanic(pgdat, size, align, goal, 0);
> +	return ___alloc_bootmem_node_nopanic(pgdat, size, align, goal,
> +			0, flags);
>   }
>   
>   void * __init ___alloc_bootmem_node(pg_data_t *pgdat, unsigned long size,
> @@ -329,7 +334,7 @@ void * __init ___alloc_bootmem_node(pg_d
>   {
>   	void *ptr;
>   
> -	ptr = ___alloc_bootmem_node_nopanic(pgdat, size, align, goal, limit);
> +	ptr = ___alloc_bootmem_node_nopanic(pgdat, size, align, goal, limit, 0);
>   	if (ptr)
>   		return ptr;
>   
> @@ -354,7 +359,7 @@ void * __init ___alloc_bootmem_node(pg_d
>    * The function panics if the request can not be satisfied.
>    */
>   void * __init __alloc_bootmem_node(pg_data_t *pgdat, unsigned long size,
> -				   unsigned long align, unsigned long goal)
> +			unsigned long align, unsigned long goal)
>   {
>   	if (WARN_ON_ONCE(slab_is_available()))
>   		return kzalloc_node(size, GFP_NOWAIT, pgdat->node_id);
> @@ -388,7 +393,7 @@ void * __init __alloc_bootmem_node_high(
>   void * __init __alloc_bootmem_low(unsigned long size, unsigned long align,
>   				  unsigned long goal)
>   {
> -	return ___alloc_bootmem(size, align, goal, ARCH_LOW_ADDRESS_LIMIT);
> +	return ___alloc_bootmem(size, align, goal, ARCH_LOW_ADDRESS_LIMIT, 0);
>   }
>   
>   void * __init __alloc_bootmem_low_nopanic(unsigned long size,
> @@ -396,7 +401,7 @@ void * __init __alloc_bootmem_low_nopani
>   					  unsigned long goal)
>   {
>   	return ___alloc_bootmem_nopanic(size, align, goal,
> -					ARCH_LOW_ADDRESS_LIMIT);
> +					ARCH_LOW_ADDRESS_LIMIT, 0);
>   }
>   
>   /**
> Index: linux/mm/sparse.c
> ===================================================================
> --- linux.orig/mm/sparse.c
> +++ linux/mm/sparse.c
> @@ -281,7 +281,7 @@ sparse_early_usemaps_alloc_pgdat_section
>   	nid = early_pfn_to_nid(goal >> PAGE_SHIFT);
>   again:
>   	p = ___alloc_bootmem_node_nopanic(NODE_DATA(nid), size,
> -					  SMP_CACHE_BYTES, goal, limit);
> +					  SMP_CACHE_BYTES, goal, limit, 0);
>   	if (!p && limit) {
>   		limit = 0;
>   		goto again;
> Index: linux/mm/hugetlb.c
> ===================================================================
> --- linux.orig/mm/hugetlb.c
> +++ linux/mm/hugetlb.c
> @@ -1188,7 +1188,8 @@ int __weak alloc_bootmem_huge_page(struc
>   		addr = __alloc_bootmem_node_nopanic(
>   				NODE_DATA(hstate_next_node_to_alloc(h,
>   						&node_states[N_MEMORY])),
> -				huge_page_size(h), huge_page_size(h), 0);
> +				huge_page_size(h), huge_page_size(h),
> +				0, NO_ZERO);
>   
>   		if (addr) {
>   			/*
> Index: linux/mm/bootmem.c
> ===================================================================
> --- linux.orig/mm/bootmem.c
> +++ linux/mm/bootmem.c
> @@ -660,7 +660,7 @@ restart:
>    * Returns NULL on failure.
>    */
>   void * __init __alloc_bootmem_nopanic(unsigned long size, unsigned long align,
> -					unsigned long goal)
> +					unsigned long goal, u32 flags)
>   {
>   	unsigned long limit = 0;
>   
> @@ -705,7 +705,8 @@ void * __init __alloc_bootmem(unsigned l
>   
>   void * __init ___alloc_bootmem_node_nopanic(pg_data_t *pgdat,
>   				unsigned long size, unsigned long align,
> -				unsigned long goal, unsigned long limit)
> +				unsigned long goal, unsigned long limit,
> +				u32 flags)
>   {
>   	void *ptr;
>   
> @@ -734,12 +735,13 @@ again:
>   }
>   
>   void * __init __alloc_bootmem_node_nopanic(pg_data_t *pgdat, unsigned long size,
> -				   unsigned long align, unsigned long goal)
> +			unsigned long align, unsigned long goal, u32 flags)
>   {
>   	if (WARN_ON_ONCE(slab_is_available()))
>   		return kzalloc_node(size, GFP_NOWAIT, pgdat->node_id);
>   
> -	return ___alloc_bootmem_node_nopanic(pgdat, size, align, goal, 0);
> +	return ___alloc_bootmem_node_nopanic(pgdat, size, align, goal,
> +					     0, flags);
>   }
>   
>   void * __init ___alloc_bootmem_node(pg_data_t *pgdat, unsigned long size,
> @@ -748,7 +750,7 @@ void * __init ___alloc_bootmem_node(pg_d
>   {
>   	void *ptr;
>   
> -	ptr = ___alloc_bootmem_node_nopanic(pgdat, size, align, goal, 0);
> +	ptr = ___alloc_bootmem_node_nopanic(pgdat, size, align, goal, 0, 0);
>   	if (ptr)
>   		return ptr;
>   
> Index: linux/mm/page_cgroup.c
> ===================================================================
> --- linux.orig/mm/page_cgroup.c
> +++ linux/mm/page_cgroup.c
> @@ -55,7 +55,7 @@ static int __init alloc_node_page_cgroup
>   	table_size = sizeof(struct page_cgroup) * nr_pages;
>   
>   	base = __alloc_bootmem_node_nopanic(NODE_DATA(nid),
> -			table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
> +			table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS), 0);
>   	if (!base)
>   		return -ENOMEM;
>   	NODE_DATA(nid)->node_page_cgroup = base;
>
> --
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> see: http://www.linux-mm.org/ .
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