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Date: Wed, 22 Dec 2021 09:10:07 +0000
From: SeongJae Park <sj@...nel.org>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: sj@...nel.org, akpm@...ux-foundation.org, mike.kravetz@...cle.com,
linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/damon: Add access checking for hugetlb pages
Hi Baolin,
Basically, the code looks ok to me. I left so trivial cosmetic nitpicks below,
though.
On Thu, 16 Dec 2021 18:38:03 +0800 Baolin Wang <baolin.wang@...ux.alibaba.com> wrote:
> The process's VMAs can be mapped by hugetlb page, but now the DAMON
> did not implement the access checking for hugetlb pte, so we can not
> get the actual access count like below if a process VMAs were mapped
> by hugetlb.
>
> damon_aggregated: target_id=18446614368406014464
> nr_regions=12 4194304-5476352: 0 545
> damon_aggregated: target_id=18446614368406014464
> nr_regions=12 140662370467840-140662372970496: 0 545
> damon_aggregated: target_id=18446614368406014464
> nr_regions=12 140662372970496-140662375460864: 0 545
> damon_aggregated: target_id=18446614368406014464
> nr_regions=12 140662375460864-140662377951232: 0 545
> damon_aggregated: target_id=18446614368406014464
> nr_regions=12 140662377951232-140662380449792: 0 545
> damon_aggregated: target_id=18446614368406014464
> nr_regions=12 140662380449792-140662382944256: 0 545
> ......
I'd prefer indenting the program output with 4 spaces and not wrapping it.
e.g.,
damon_aggregated: target_id=18446614368406014464 nr_regions=12 4194304-5476352: 0 545
damon_aggregated: target_id=18446614368406014464 nr_regions=12 140662370467840-140662372970496: 0 545
>
> Thus this patch adds hugetlb access checking support, with this patch
> we can see below VMA mapped by hugetlb access count.
>
> damon_aggregated: target_id=18446613056935405824
> nr_regions=12 140296486649856-140296489914368: 1 3
> damon_aggregated: target_id=18446613056935405824
> nr_regions=12 140296489914368-140296492978176: 1 3
> damon_aggregated: target_id=18446613056935405824
> nr_regions=12 140296492978176-140296495439872: 1 3
> damon_aggregated: target_id=18446613056935405824
> nr_regions=12 140296495439872-140296498311168: 1 3
> damon_aggregated: target_id=18446613056935405824
> nr_regions=12 140296498311168-140296501198848: 1 3
> damon_aggregated: target_id=18446613056935405824
> nr_regions=12 140296501198848-140296504320000: 1 3
> damon_aggregated: target_id=18446613056935405824
> nr_regions=12 140296504320000-140296507568128: 1 2
> ......
ditto.
>
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> ---
> Changes from v1:
> - Move damon_hugetlb_mkold() to vaddr.c file.
> - Move some assignments in the variables definitions.
> ---
> mm/damon/vaddr.c | 96 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 96 insertions(+)
>
> diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
> index 78ff2bc..69c436b 100644
> --- a/mm/damon/vaddr.c
> +++ b/mm/damon/vaddr.c
> @@ -386,8 +386,65 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned long addr,
> return 0;
> }
>
> +#ifdef CONFIG_HUGETLB_PAGE
> +static void damon_hugetlb_mkold(pte_t *pte, struct mm_struct *mm,
> + struct vm_area_struct *vma, unsigned long addr)
> +{
> + bool referenced = false;
> + struct hstate *h = hstate_vma(vma);
> + pte_t entry = huge_ptep_get(pte);
> + struct page *page = pte_page(entry);
> +
> + if (!page)
> + return;
> +
> + get_page(page);
> +
> + if (pte_young(entry)) {
> + referenced = true;
> + entry = pte_mkold(entry);
> + huge_ptep_set_access_flags(vma, addr, pte, entry,
> + vma->vm_flags & VM_WRITE);
> + }
> +
> +#ifdef CONFIG_MMU_NOTIFIER
> + if (mmu_notifier_clear_young(mm, addr, addr + huge_page_size(h)))
> + referenced = true;
> +#endif /* CONFIG_MMU_NOTIFIER */
> +
> + if (referenced)
> + set_page_young(page);
> +
> + set_page_idle(page);
> + put_page(page);
> +}
> +
> +static int damon_mkold_hugetlb_entry(pte_t *pte, unsigned long hmask,
> + unsigned long addr, unsigned long end,
> + struct mm_walk *walk)
> +{
> + struct hstate *h = hstate_vma(walk->vma);
> + spinlock_t *ptl;
> + pte_t entry;
> +
> + ptl = huge_pte_lock(h, walk->mm, pte);
> + entry = huge_ptep_get(pte);
> + if (!pte_present(entry))
> + goto out;
> +
> + damon_hugetlb_mkold(pte, walk->mm, walk->vma, addr);
> +
> +out:
> + spin_unlock(ptl);
> + return 0;
> +}
> +#else
> +#define damon_mkold_hugetlb_entry NULL
> +#endif
Could we append a comment saying this #endif is for #ifdef CONFIG_HUGETLB_PAGE,
like below?
#endif /* CONFIG_HUGETLB_PAGE */
> +
> static const struct mm_walk_ops damon_mkold_ops = {
> .pmd_entry = damon_mkold_pmd_entry,
> + .hugetlb_entry = damon_mkold_hugetlb_entry,
> };
>
> static void damon_va_mkold(struct mm_struct *mm, unsigned long addr)
> @@ -482,8 +539,47 @@ static int damon_young_pmd_entry(pmd_t *pmd, unsigned long addr,
> return 0;
> }
>
> +#ifdef CONFIG_HUGETLB_PAGE
> +static int damon_young_hugetlb_entry(pte_t *pte, unsigned long hmask,
> + unsigned long addr, unsigned long end,
> + struct mm_walk *walk)
> +{
> + struct damon_young_walk_private *priv = walk->private;
> + struct hstate *h = hstate_vma(walk->vma);
> + struct page *page;
> + spinlock_t *ptl;
> + pte_t entry;
> +
> + ptl = huge_pte_lock(h, walk->mm, pte);
> + entry = huge_ptep_get(pte);
> + if (!pte_present(entry))
> + goto out;
> +
> + page = pte_page(entry);
> + if (!page)
> + goto out;
> +
> + get_page(page);
> +
> + if (pte_young(entry) || !page_is_idle(page) ||
> + mmu_notifier_test_young(walk->mm, addr)) {
> + *priv->page_sz = huge_page_size(h);
> + priv->young = true;
> + }
> +
> + put_page(page);
> +
> +out:
> + spin_unlock(ptl);
> + return 0;
> +}
> +#else
> +#define damon_young_hugetlb_entry NULL
> +#endif
ditto.
> +
> static const struct mm_walk_ops damon_young_ops = {
> .pmd_entry = damon_young_pmd_entry,
> + .hugetlb_entry = damon_young_hugetlb_entry,
> };
>
> static bool damon_va_young(struct mm_struct *mm, unsigned long addr,
> --
> 1.8.3.1
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