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SubjectRe: [PATCH] mm/damon: Add access checking for hugetlb pages
From
Hi,

On 12/16/2021 1:16 AM, SeongJae Park wrote:
> On Wed, 15 Dec 2021 23:23:25 +0800 Baolin Wang <baolin.wang@linux.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
>> ......
>>
>> 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
>> ......
>
> Thank you for this patch!
>
>>
>> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>> ---
>> mm/damon/prmtv-common.c | 37 ++++++++++++++++++++++++++++
>> mm/damon/prmtv-common.h | 11 +++++++++
>> mm/damon/vaddr.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++
>> 3 files changed, 113 insertions(+)
>>
>> diff --git a/mm/damon/prmtv-common.c b/mm/damon/prmtv-common.c
>> index 92a04f5..155afb8 100644
>> --- a/mm/damon/prmtv-common.c
>> +++ b/mm/damon/prmtv-common.c
>> @@ -9,6 +9,7 @@
>> #include <linux/page_idle.h>
>> #include <linux/pagemap.h>
>> #include <linux/rmap.h>
>> +#include <linux/hugetlb.h>
>>
>> #include "prmtv-common.h"
>>
>> @@ -86,6 +87,42 @@ void damon_pmdp_mkold(pmd_t *pmd, struct mm_struct *mm, unsigned long addr)
>> #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>> }
>>
>> +#ifdef CONFIG_HUGETLB_PAGE
>> +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;
>> + struct page *page;
>> +
>> + entry = huge_ptep_get(pte);
>> + page = pte_page(entry);
>
> Could we do these assignments in above definition part like this?

Sure.

>
> 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);
>> +}
>> +#endif
>> +
>> #define DAMON_MAX_SUBSCORE (100)
>> #define DAMON_MAX_AGE_IN_LOG (32)
>>
>> diff --git a/mm/damon/prmtv-common.h b/mm/damon/prmtv-common.h
>> index e790cb5..65efcb7 100644
>> --- a/mm/damon/prmtv-common.h
>> +++ b/mm/damon/prmtv-common.h
>> @@ -12,5 +12,16 @@
>> void damon_ptep_mkold(pte_t *pte, struct mm_struct *mm, unsigned long addr);
>> void damon_pmdp_mkold(pmd_t *pmd, struct mm_struct *mm, unsigned long addr);
>>
>> +#ifdef CONFIG_HUGETLB_PAGE
>> +void damon_hugetlb_mkold(pte_t *pte, struct mm_struct *mm,
>> + struct vm_area_struct *vma, unsigned long addr);
>> +#else
>> +static inline void damon_hugetlb_mkold(pte_t *pte, struct mm_struct *mm,
>> + struct vm_area_struct *vma,
>> + unsigned long addr)
>> +{
>> +}
>> +#endif
>> +
>
> Seems damon_hugetlb_mkold() is called from only vaddr.c. Could you move the
> definition into vaddr.c and remove this change in prmtv-common.h?

Sure.

>
>> int damon_pageout_score(struct damon_ctx *c, struct damon_region *r,
>> struct damos *s);
>> diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
>> index 78ff2bc..ee116e5 100644
>> --- a/mm/damon/vaddr.c
>> +++ b/mm/damon/vaddr.c
>> @@ -14,6 +14,7 @@
>> #include <linux/page_idle.h>
>> #include <linux/pagewalk.h>
>> #include <linux/sched/mm.h>
>> +#include <linux/hugetlb.h>
>>
>> #include "prmtv-common.h"
>>
>> @@ -386,8 +387,33 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned long addr,
>> return 0;
>> }
>>
>> +#ifdef CONFIG_HUGETLB_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);
>
> Could we do above assignments in the variables definitions?

Since we need get the hugetlb pte under the pte lock, I still perfer to
declare the lock region explicitly in the code instead in the variables
definitions.

>
>> + 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
>> +
>> 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 +508,47 @@ 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);
>
> Could we do these assignments in the above variables definitions?

Ditto.

Thanks for your comments.

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