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Date: Wed, 30 May 2012 18:56:36 -0700 (PDT)
From: David Rientjes <rientjes@...gle.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
cc: linux-mm@...ck.org,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
dhillf@...il.com, mhocko@...e.cz,
Andrew Morton <akpm@...ux-foundation.org>, hannes@...xchg.org,
linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [PATCH -V7 04/14] hugetlb: use mmu_gather instead of a temporary
linked list for accumulating pages
On Wed, 30 May 2012, Aneesh Kumar K.V wrote:
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index cc9281b..ff233e4 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -416,8 +416,8 @@ hugetlb_vmtruncate_list(struct prio_tree_root *root, pgoff_t pgoff)
> else
> v_offset = 0;
>
> - __unmap_hugepage_range(vma,
> - vma->vm_start + v_offset, vma->vm_end, NULL);
> + unmap_hugepage_range(vma, vma->vm_start + v_offset,
> + vma->vm_end, NULL);
> }
> }
>
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 217f528..c21e136 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -7,6 +7,7 @@
>
> struct ctl_table;
> struct user_struct;
> +struct mmu_gather;
>
> #ifdef CONFIG_HUGETLB_PAGE
>
> @@ -40,9 +41,10 @@ int follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *,
> struct page **, struct vm_area_struct **,
> unsigned long *, int *, int, unsigned int flags);
> void unmap_hugepage_range(struct vm_area_struct *,
> - unsigned long, unsigned long, struct page *);
> -void __unmap_hugepage_range(struct vm_area_struct *,
> - unsigned long, unsigned long, struct page *);
> + unsigned long, unsigned long, struct page *);
> +void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vms,
s/vms/vma/
> + unsigned long start, unsigned long end,
> + struct page *ref_page);
> int hugetlb_prefault(struct address_space *, struct vm_area_struct *);
> void hugetlb_report_meminfo(struct seq_file *);
> int hugetlb_report_node_meminfo(int, char *);
> @@ -98,7 +100,6 @@ static inline unsigned long hugetlb_total_pages(void)
> #define follow_huge_addr(mm, addr, write) ERR_PTR(-EINVAL)
> #define copy_hugetlb_page_range(src, dst, vma) ({ BUG(); 0; })
> #define hugetlb_prefault(mapping, vma) ({ BUG(); 0; })
> -#define unmap_hugepage_range(vma, start, end, page) BUG()
> static inline void hugetlb_report_meminfo(struct seq_file *m)
> {
> }
Why?
> @@ -112,13 +113,24 @@ static inline void hugetlb_report_meminfo(struct seq_file *m)
> #define hugetlb_free_pgd_range(tlb, addr, end, floor, ceiling) ({BUG(); 0; })
> #define hugetlb_fault(mm, vma, addr, flags) ({ BUG(); 0; })
> #define huge_pte_offset(mm, address) 0
> -#define dequeue_hwpoisoned_huge_page(page) 0
> +static inline int dequeue_hwpoisoned_huge_page(struct page *page)
> +{
> + return 0;
> +}
> +
Unrelated from this patchset.
> static inline void copy_huge_page(struct page *dst, struct page *src)
> {
> }
>
> #define hugetlb_change_protection(vma, address, end, newprot)
>
> +static inline void __unmap_hugepage_range(struct mmu_gather *tlb,
> + struct vm_area_struct *vma, unsigned long start,
> + unsigned long end, struct page *ref_page)
> +{
> + BUG();
> +}
> +
I think this should be done under the unmap_hugepage_range() definition
you removed (and change it to be a static inline function as well).
> #endif /* !CONFIG_HUGETLB_PAGE */
>
> #define HUGETLB_ANON_FILE "anon_hugepage"
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 9b97a5c..704a269 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -24,8 +24,9 @@
>
> #include <asm/page.h>
> #include <asm/pgtable.h>
> -#include <linux/io.h>
> +#include <asm/tlb.h>
>
> +#include <linux/io.h>
> #include <linux/hugetlb.h>
> #include <linux/node.h>
> #include "internal.h"
> @@ -2310,30 +2311,26 @@ static int is_hugetlb_entry_hwpoisoned(pte_t pte)
> return 0;
> }
>
> -void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
> - unsigned long end, struct page *ref_page)
> +void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
> + unsigned long start, unsigned long end,
> + struct page *ref_page)
> {
> + int force_flush = 0;
Can this be bool?
> struct mm_struct *mm = vma->vm_mm;
> unsigned long address;
> pte_t *ptep;
> pte_t pte;
> struct page *page;
> - struct page *tmp;
> struct hstate *h = hstate_vma(vma);
> unsigned long sz = huge_page_size(h);
>
> - /*
> - * A page gathering list, protected by per file i_mmap_mutex. The
> - * lock is used to avoid list corruption from multiple unmapping
> - * of the same page since we are using page->lru.
> - */
> - LIST_HEAD(page_list);
> -
> WARN_ON(!is_vm_hugetlb_page(vma));
> BUG_ON(start & ~huge_page_mask(h));
> BUG_ON(end & ~huge_page_mask(h));
>
> + tlb_start_vma(tlb, vma);
> mmu_notifier_invalidate_range_start(mm, start, end);
> +again:
> spin_lock(&mm->page_table_lock);
> for (address = start; address < end; address += sz) {
> ptep = huge_pte_offset(mm, address);
> @@ -2372,30 +2369,45 @@ void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
> }
>
> pte = huge_ptep_get_and_clear(mm, address, ptep);
> + tlb_remove_tlb_entry(tlb, ptep, address);
> if (pte_dirty(pte))
> set_page_dirty(page);
> - list_add(&page->lru, &page_list);
>
> + page_remove_rmap(page);
> + force_flush = !__tlb_remove_page(tlb, page);
> + if (force_flush)
> + break;
> /* Bail out after unmapping reference page if supplied */
> if (ref_page)
> break;
> }
> - flush_tlb_range(vma, start, end);
> spin_unlock(&mm->page_table_lock);
> - mmu_notifier_invalidate_range_end(mm, start, end);
> - list_for_each_entry_safe(page, tmp, &page_list, lru) {
> - page_remove_rmap(page);
> - list_del(&page->lru);
> - put_page(page);
> + /*
> + * mmu_gather ran out of room to batch pages, we break out of
> + * the PTE lock to avoid doing the potential expensive TLB invalidate
> + * and page-free while holding it.
> + */
> + if (force_flush) {
> + force_flush = 0;
> + tlb_flush_mmu(tlb);
> + if (address < end && !ref_page)
> + goto again;
Shouldn't be copying "start" at the beginning of this function and then
updating that copy now and use it as the loop initialization?
> }
> + mmu_notifier_invalidate_range_end(mm, start, end);
> + tlb_end_vma(tlb, vma);
> }
>
> void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
> unsigned long end, struct page *ref_page)
> {
> - mutex_lock(&vma->vm_file->f_mapping->i_mmap_mutex);
> - __unmap_hugepage_range(vma, start, end, ref_page);
> - mutex_unlock(&vma->vm_file->f_mapping->i_mmap_mutex);
> + struct mm_struct *mm;
> + struct mmu_gather tlb;
> +
> + mm = vma->vm_mm;
> +
> + tlb_gather_mmu(&tlb, mm, 0);
> + __unmap_hugepage_range(&tlb, vma, start, end, ref_page);
> + tlb_finish_mmu(&tlb, start, end);
> }
>
> /*
--
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