linux-kernel - Re: [patch] mm, memcg: sync allocation and memcg charge gfp flags for thp fix fix

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Message-ID: <20150403105014.GB6216@dhcp22.suse.cz>
Date:	Fri, 3 Apr 2015 12:50:14 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch] mm, memcg: sync allocation and memcg charge gfp flags
 for thp fix fix

On Thu 02-04-15 18:41:18, David Rientjes wrote:
> "mm, memcg: sync allocation and memcg charge gfp flags for THP" in -mm 
> introduces a formal to pass the gfp mask for khugepaged's hugepage 
> allocation.  This is just too ugly to live.
> 
> alloc_hugepage_gfpmask() cannot differ between NUMA and UMA configs by 
> anything in GFP_RECLAIM_MASK, which is the only thing that matters for 
> memcg reclaim, so just determine the gfp flags once in 
> collapse_huge_page() and avoid the complexity.
> 
> Signed-off-by: David Rientjes <rientjes@...gle.com>

Thanks for this cleanup!

Acked-by: Michal Hocko <mhocko@...e.cz>
> ---
>  -mm: intended to be folded into
>       mm-memcg-sync-allocation-and-memcg-charge-gfp-flags-for-thp.patch
> 
>  mm/huge_memory.c | 21 ++++++++-------------
>  1 file changed, 8 insertions(+), 13 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2373,16 +2373,12 @@ static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
>  }
>  
>  static struct page *
> -khugepaged_alloc_page(struct page **hpage, gfp_t *gfp, struct mm_struct *mm,
> +khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
>  		       struct vm_area_struct *vma, unsigned long address,
>  		       int node)
>  {
>  	VM_BUG_ON_PAGE(*hpage, *hpage);
>  
> -	/* Only allocate from the target node */
> -	*gfp = alloc_hugepage_gfpmask(khugepaged_defrag(), __GFP_OTHER_NODE) |
> -	        __GFP_THISNODE;
> -
>  	/*
>  	 * Before allocating the hugepage, release the mmap_sem read lock.
>  	 * The allocation can take potentially a long time if it involves
> @@ -2391,7 +2387,7 @@ khugepaged_alloc_page(struct page **hpage, gfp_t *gfp, struct mm_struct *mm,
>  	 */
>  	up_read(&mm->mmap_sem);
>  
> -	*hpage = alloc_pages_exact_node(node, *gfp, HPAGE_PMD_ORDER);
> +	*hpage = alloc_pages_exact_node(node, gfp, HPAGE_PMD_ORDER);
>  	if (unlikely(!*hpage)) {
>  		count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
>  		*hpage = ERR_PTR(-ENOMEM);
> @@ -2445,18 +2441,13 @@ static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
>  }
>  
>  static struct page *
> -khugepaged_alloc_page(struct page **hpage, gfp_t *gfp, struct mm_struct *mm,
> +khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
>  		       struct vm_area_struct *vma, unsigned long address,
>  		       int node)
>  {
>  	up_read(&mm->mmap_sem);
>  	VM_BUG_ON(!*hpage);
>  
> -	/*
> -	 * khugepaged_alloc_hugepage is doing the preallocation, use the same
> -	 * gfp flags here.
> -	 */
> -	*gfp = alloc_hugepage_gfpmask(khugepaged_defrag(), 0);
>  	return  *hpage;
>  }
>  #endif
> @@ -2495,8 +2486,12 @@ static void collapse_huge_page(struct mm_struct *mm,
>  
>  	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
>  
> +	/* Only allocate from the target node */
> +	gfp = alloc_hugepage_gfpmask(khugepaged_defrag(), __GFP_OTHER_NODE) |
> +		__GFP_THISNODE;
> +
>  	/* release the mmap_sem read lock. */
> -	new_page = khugepaged_alloc_page(hpage, &gfp, mm, vma, address, node);
> +	new_page = khugepaged_alloc_page(hpage, gfp, mm, vma, address, node);
>  	if (!new_page)
>  		return;
>  
> 
> --
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-- 
Michal Hocko
SUSE Labs
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