Re: [PATCH 1/2] Revert "Revert "mm, thp: consolidate THP gfp handling into alloc_hugepage_direct_gfpmask""

[Michal Hocko]

On Fri 03-05-19 18:31:45, Andrea Arcangeli wrote:
> This reverts commit 356ff8a9a78fb35d6482584d260c3754dcbdf669.

This should really provide some changelog. I would go with the
following.

"
Consolidation of the THP allocation flags at the same place was meant to
be a clean up to easier handle otherwise scattered code which is
imposing a maintenance burden. There were no real problems observed with
the gfp mask consilidation but the reverting it was rushed through
without a larger consensus regardless.

This patch brings the consolidation back because this should make the
long term maintainability easier as well as it should allow future
changes to be less error prone.
"

Feel free to reuse or use your own wording

> Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>

With a changelog clarification feel free to add
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
>  include/linux/gfp.h | 12 ++++--------
>  mm/huge_memory.c    | 27 ++++++++++++++-------------
>  mm/mempolicy.c      | 32 +++-----------------------------
>  mm/shmem.c          |  2 +-
>  4 files changed, 22 insertions(+), 51 deletions(-)
> 
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index fdab7de7490d..e2a6aea3f8ec 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -510,22 +510,18 @@ 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, bool hugepage);
> -#define alloc_hugepage_vma(gfp_mask, vma, addr, order) \
> -	alloc_pages_vma(gfp_mask, order, vma, addr, numa_node_id(), true)
> +			int node);
>  #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, false)\
> -	alloc_pages(gfp_mask, order)
> -#define alloc_hugepage_vma(gfp_mask, vma, addr, order) \
> +#define alloc_pages_vma(gfp_mask, order, vma, addr, node)\
>  	alloc_pages(gfp_mask, order)
>  #endif
>  #define alloc_page(gfp_mask) alloc_pages(gfp_mask, 0)
>  #define alloc_page_vma(gfp_mask, vma, addr)			\
> -	alloc_pages_vma(gfp_mask, 0, vma, addr, numa_node_id(), false)
> +	alloc_pages_vma(gfp_mask, 0, vma, addr, numa_node_id())
>  #define alloc_page_vma_node(gfp_mask, vma, addr, node)		\
> -	alloc_pages_vma(gfp_mask, 0, vma, addr, node, false)
> +	alloc_pages_vma(gfp_mask, 0, vma, addr, node)
>  
>  extern unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order);
>  extern unsigned long get_zeroed_page(gfp_t gfp_mask);
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 165ea46bf149..7efe68ba052a 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -641,30 +641,30 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
>   *	    available
>   * never: never stall for any thp allocation
>   */
> -static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
> +static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma, unsigned long addr)
>  {
>  	const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
> +	const gfp_t gfp_mask = GFP_TRANSHUGE_LIGHT | __GFP_THISNODE;
>  
>  	/* Always do synchronous compaction */
>  	if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
> -		return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
> +		return GFP_TRANSHUGE | __GFP_THISNODE |
> +		       (vma_madvised ? 0 : __GFP_NORETRY);
>  
>  	/* Kick kcompactd and fail quickly */
>  	if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
> -		return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
> +		return gfp_mask | __GFP_KSWAPD_RECLAIM;
>  
>  	/* Synchronous compaction if madvised, otherwise kick kcompactd */
>  	if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
> -		return GFP_TRANSHUGE_LIGHT |
> -			(vma_madvised ? __GFP_DIRECT_RECLAIM :
> -					__GFP_KSWAPD_RECLAIM);
> +		return gfp_mask | (vma_madvised ? __GFP_DIRECT_RECLAIM :
> +						  __GFP_KSWAPD_RECLAIM);
>  
>  	/* Only do synchronous compaction if madvised */
>  	if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
> -		return GFP_TRANSHUGE_LIGHT |
> -		       (vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
> +		return gfp_mask | (vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
>  
> -	return GFP_TRANSHUGE_LIGHT;
> +	return gfp_mask;
>  }
>  
>  /* Caller must hold page table lock. */
> @@ -736,8 +736,8 @@ vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
>  			pte_free(vma->vm_mm, pgtable);
>  		return ret;
>  	}
> -	gfp = alloc_hugepage_direct_gfpmask(vma);
> -	page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
> +	gfp = alloc_hugepage_direct_gfpmask(vma, haddr);
> +	page = alloc_pages_vma(gfp, HPAGE_PMD_ORDER, vma, haddr, numa_node_id());
>  	if (unlikely(!page)) {
>  		count_vm_event(THP_FAULT_FALLBACK);
>  		return VM_FAULT_FALLBACK;
> @@ -1340,8 +1340,9 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
>  alloc:
>  	if (__transparent_hugepage_enabled(vma) &&
>  	    !transparent_hugepage_debug_cow()) {
> -		huge_gfp = alloc_hugepage_direct_gfpmask(vma);
> -		new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
> +		huge_gfp = alloc_hugepage_direct_gfpmask(vma, haddr);
> +		new_page = alloc_pages_vma(huge_gfp, HPAGE_PMD_ORDER, vma,
> +				haddr, numa_node_id());
>  	} else
>  		new_page = NULL;
>  
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 2219e747df49..74e44000ad61 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -1142,8 +1142,8 @@ static struct page *new_page(struct page *page, unsigned long start)
>  	} else if (PageTransHuge(page)) {
>  		struct page *thp;
>  
> -		thp = alloc_hugepage_vma(GFP_TRANSHUGE, vma, address,
> -					 HPAGE_PMD_ORDER);
> +		thp = alloc_pages_vma(GFP_TRANSHUGE, HPAGE_PMD_ORDER, vma,
> +				address, numa_node_id());
>  		if (!thp)
>  			return NULL;
>  		prep_transhuge_page(thp);
> @@ -2037,7 +2037,6 @@ static struct page *alloc_page_interleave(gfp_t gfp, unsigned order,
>   * 	@vma:  Pointer to VMA or NULL if not available.
>   *	@addr: Virtual Address of the allocation. Must be inside the VMA.
>   *	@node: Which node to prefer for allocation (modulo policy).
> - *	@hugepage: for hugepages try only the preferred node if possible
>   *
>   * 	This function allocates a page from the kernel page pool and applies
>   *	a NUMA policy associated with the VMA or the current process.
> @@ -2048,7 +2047,7 @@ static struct page *alloc_page_interleave(gfp_t gfp, unsigned order,
>   */
>  struct page *
>  alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
> -		unsigned long addr, int node, bool hugepage)
> +		unsigned long addr, int node)
>  {
>  	struct mempolicy *pol;
>  	struct page *page;
> @@ -2066,31 +2065,6 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
>  		goto out;
>  	}
>  
> -	if (unlikely(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && hugepage)) {
> -		int hpage_node = node;
> -
> -		/*
> -		 * For hugepage allocation and non-interleave policy which
> -		 * allows the current node (or other explicitly preferred
> -		 * node) we only try to allocate from the current/preferred
> -		 * node and don't fall back to other nodes, as the cost of
> -		 * remote accesses would likely offset THP benefits.
> -		 *
> -		 * If the policy is interleave, or does not allow the current
> -		 * node in its nodemask, we allocate the standard way.
> -		 */
> -		if (pol->mode == MPOL_PREFERRED && !(pol->flags & MPOL_F_LOCAL))
> -			hpage_node = pol->v.preferred_node;
> -
> -		nmask = policy_nodemask(gfp, pol);
> -		if (!nmask || node_isset(hpage_node, *nmask)) {
> -			mpol_cond_put(pol);
> -			page = __alloc_pages_node(hpage_node,
> -						gfp | __GFP_THISNODE, order);
> -			goto out;
> -		}
> -	}
> -
>  	nmask = policy_nodemask(gfp, pol);
>  	preferred_nid = policy_node(gfp, pol, node);
>  	page = __alloc_pages_nodemask(gfp, order, preferred_nid, nmask);
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 2275a0ff7c30..ed7ebc423c6b 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1464,7 +1464,7 @@ static struct page *shmem_alloc_hugepage(gfp_t gfp,
>  
>  	shmem_pseudo_vma_init(&pvma, info, hindex);
>  	page = alloc_pages_vma(gfp | __GFP_COMP | __GFP_NORETRY | __GFP_NOWARN,
> -			HPAGE_PMD_ORDER, &pvma, 0, numa_node_id(), true);
> +			HPAGE_PMD_ORDER, &pvma, 0, numa_node_id());
>  	shmem_pseudo_vma_destroy(&pvma);
>  	if (page)
>  		prep_transhuge_page(page);

-- 
Michal Hocko
SUSE Labs