Re: [PATCH V2] mm/thp: Allocate transparent hugepages on local node

[Kirill A. Shutemov]

On Mon, Dec 01, 2014 at 11:16:43AM +0530, Aneesh Kumar K.V wrote:
> This make sure that we try to allocate hugepages from local node if
> allowed by mempolicy. If we can't, we fallback to small page allocation
> based on mempolicy. This is based on the observation that allocating pages
> on local node is more beneficial that allocating hugepages on remote node.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> ---
>  include/linux/gfp.h |  4 ++++
>  mm/huge_memory.c    | 24 +++++++++---------------
>  mm/mempolicy.c      | 40 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 53 insertions(+), 15 deletions(-)
> 
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index 41b30fd4d041..fcbd017b4fb4 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -338,11 +338,15 @@ alloc_pages(gfp_t gfp_mask, unsigned int order)
>  extern struct page *alloc_pages_vma(gfp_t gfp_mask, int order,
>  			struct vm_area_struct *vma, unsigned long addr,
>  			int node);
> +extern struct page *alloc_hugepage_vma(gfp_t gfp, struct vm_area_struct *vma,
> +				       unsigned long addr, int order);
>  #else
>  #define alloc_pages(gfp_mask, order) \
>  		alloc_pages_node(numa_node_id(), gfp_mask, order)
>  #define alloc_pages_vma(gfp_mask, order, vma, addr, node)	\
>  	alloc_pages(gfp_mask, order)
> +#define alloc_hugepage_vma(gfp_mask, vma, addr, order)	\
> +	alloc_pages(gfp_mask, order)
>  #endif
>  #define alloc_page(gfp_mask) alloc_pages(gfp_mask, 0)
>  #define alloc_page_vma(gfp_mask, vma, addr)			\
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index de984159cf0b..7903eb995b7f 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -766,15 +766,6 @@ static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
>  	return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
>  }
>  
> -static inline struct page *alloc_hugepage_vma(int defrag,
> -					      struct vm_area_struct *vma,
> -					      unsigned long haddr, int nd,
> -					      gfp_t extra_gfp)
> -{
> -	return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp),
> -			       HPAGE_PMD_ORDER, vma, haddr, nd);
> -}
> -
>  /* Caller must hold page table lock. */
>  static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
>  		struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
> @@ -796,6 +787,7 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
>  			       unsigned long address, pmd_t *pmd,
>  			       unsigned int flags)
>  {
> +	gfp_t gfp;
>  	struct page *page;
>  	unsigned long haddr = address & HPAGE_PMD_MASK;
>  
> @@ -830,8 +822,8 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
>  		}
>  		return 0;
>  	}
> -	page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
> -			vma, haddr, numa_node_id(), 0);
> +	gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
> +	page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
>  	if (unlikely(!page)) {
>  		count_vm_event(THP_FAULT_FALLBACK);
>  		return VM_FAULT_FALLBACK;
> @@ -1119,10 +1111,12 @@ int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
>  	spin_unlock(ptl);
>  alloc:
>  	if (transparent_hugepage_enabled(vma) &&
> -	    !transparent_hugepage_debug_cow())
> -		new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
> -					      vma, haddr, numa_node_id(), 0);
> -	else
> +	    !transparent_hugepage_debug_cow()) {
> +		gfp_t gfp;
> +
> +		gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
> +		new_page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);

Should node of page we're handling wp-fault for be part of decision?

> +	} else
>  		new_page = NULL;
>  
>  	if (unlikely(!new_page)) {
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index e58725aff7e9..fa96af5b31f7 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -2041,6 +2041,46 @@ retry_cpuset:
>  	return page;
>  }
>  
> +struct page *alloc_hugepage_vma(gfp_t gfp, struct vm_area_struct *vma,
> +				unsigned long addr, int order)
> +{
> +	struct page *page;
> +	nodemask_t *nmask;
> +	struct mempolicy *pol;
> +	int node = numa_node_id();

Hm. What if the code will be preempted and scheduled on different node?
I'm not really familiar with mempolicy details and not sure if we should
care. Probably not.

> +	unsigned int cpuset_mems_cookie;
> +
> +retry_cpuset:
> +	pol = get_vma_policy(vma, addr);
> +	cpuset_mems_cookie = read_mems_allowed_begin();
> +
> +	if (pol->mode != MPOL_INTERLEAVE) {
> +		/*
> +		 * For interleave policy, we don't worry about
> +		 * current node. Otherwise if current node is
> +		 * in nodemask, try to allocate hugepage from
> +		 * current node. Don't fall back to other nodes
> +		 * for THP.
> +		 */

The comment probably should be above "if ()", not below.

> +		nmask = policy_nodemask(gfp, pol);
> +		if (!nmask || node_isset(node, *nmask)) {
> +			mpol_cond_put(pol);
> +			page = alloc_pages_exact_node(node, gfp, order);
> +			if (unlikely(!page &&
> +				     read_mems_allowed_retry(cpuset_mems_cookie)))
> +				goto retry_cpuset;
> +			return page;
> +		}
> +	}
> +	mpol_cond_put(pol);
> +	/*
> +	 * if current node is not part of node mask, try
> +	 * the allocation from any node, and we can do retry
> +	 * in that case.
> +	 */
> +	return alloc_pages_vma(gfp, order, vma, addr, node);
> +}
> +
>  /**
>   * 	alloc_pages_current - Allocate pages.
>   *
> -- 
> 2.1.0
> 
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-- 
 Kirill A. Shutemov
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