On 2020-01-16 at 17:56 Michal Hocko wrote:
>On Thu 16-01-20 04:11:25, Li Xinhai wrote:
>> Checking hstate at early phase when isolating page, instead of during
>> unmap and move phase, to avoid useless isolation.
>
>Could you be more specific what you mean by isolation and why does it
>matter? The patch description should really explain _why_ the change is
>needed or desirable.
The changelog can be improved:
vma_migratable() is called to check if pages in vma can be migrated
before go ahead to isolate, unmap and move pages. For hugetlb pages,
hugepage_migration_supported(struct hstate *h) is one factor which
decide if migration is supported. In current code, this function is called
from unmap_and_move_huge_page(), after isolating page has
completed.
This patch checks hstate from vma_migratable() and avoids isolating pages
which are not supported.
>
>> Signed-off-by: Li Xinhai <lixinhai.lxh@xxxxxxxxx>
>> Cc: Michal Hocko <mhocko@xxxxxxxx>
>> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
>> ---
>> include/linux/hugetlb.h | 10 ++++++++++
>> include/linux/mempolicy.h | 29 +----------------------------
>> mm/mempolicy.c | 28 ++++++++++++++++++++++++++++
>> 3 files changed, 39 insertions(+), 28 deletions(-)
>>
>> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
>> index 31d4920..c9d871d 100644
>> --- a/include/linux/hugetlb.h
>> +++ b/include/linux/hugetlb.h
>> @@ -598,6 +598,11 @@ static inline bool hugepage_migration_supported(struct hstate *h)
>> return arch_hugetlb_migration_supported(h);
>> }
>>
>> +static inline bool vm_hugepage_migration_supported(struct vm_area_struct *vma)
>> +{
>> + return hugepage_migration_supported(hstate_vma(vma));
>> +}
>> +
>> /*
>> * Movability check is different as compared to migration check.
>> * It determines whether or not a huge page should be placed on
>> @@ -809,6 +814,11 @@ static inline bool hugepage_migration_supported(struct hstate *h)
>> return false;
>> }
>>
>> +static inline bool vm_hugepage_migration_supported(struct vm_area_struct *vma)
>> +{
>> + return false;
>> +}
>> +
>> static inline bool hugepage_movable_supported(struct hstate *h)
>> {
>> return false;
>> diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
>> index 5228c62..8165278 100644
>> --- a/include/linux/mempolicy.h
>> +++ b/include/linux/mempolicy.h
>> @@ -173,34 +173,7 @@ int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
>> extern void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol);
>>
>> /* Check if a vma is migratable */
>> -static inline bool vma_migratable(struct vm_area_struct *vma)
>> -{
>> - if (vma->vm_flags & (VM_IO | VM_PFNMAP))
>> - return false;
>> -
>> - /*
>> - * DAX device mappings require predictable access latency, so avoid
>> - * incurring periodic faults.
>> - */
>> - if (vma_is_dax(vma))
>> - return false;
>> -
>> -#ifndef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION
>> - if (vma->vm_flags & VM_HUGETLB)
>> - return false;
>> -#endif
>> -
>> - /*
>> - * Migration allocates pages in the highest zone. If we cannot
>> - * do so then migration (at least from node to node) is not
>> - * possible.
>> - */
>> - if (vma->vm_file &&
>> - gfp_zone(mapping_gfp_mask(vma->vm_file->f_mapping))
>> - < policy_zone)
>> - return false;
>> - return true;
>> -}
>> +extern bool vma_migratable(struct vm_area_struct *vma);
>>
>> extern int mpol_misplaced(struct page *, struct vm_area_struct *, unsigned long);
>> extern void mpol_put_task_policy(struct task_struct *);
>> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
>> index 067cf7d..8a01fb1 100644
>> --- a/mm/mempolicy.c
>> +++ b/mm/mempolicy.c
>> @@ -1714,6 +1714,34 @@ static int kernel_get_mempolicy(int __user *policy,
>>
>> #endif /* CONFIG_COMPAT */
>>
>> +bool vma_migratable(struct vm_area_struct *vma)
>> +{
>> + if (vma->vm_flags & (VM_IO | VM_PFNMAP))
>> + return false;
>> +
>> + /*
>> + * DAX device mappings require predictable access latency, so avoid
>> + * incurring periodic faults.
>> + */
>> + if (vma_is_dax(vma))
>> + return false;
>> +
>> + if (is_vm_hugetlb_page(vma) &&
>> + !vm_hugepage_migration_supported(vma))
>> + return false;
>> +
>> + /*
>> + * Migration allocates pages in the highest zone. If we cannot
>> + * do so then migration (at least from node to node) is not
>> + * possible.
>> + */
>> + if (vma->vm_file &&
>> + gfp_zone(mapping_gfp_mask(vma->vm_file->f_mapping))
>> + < policy_zone)
>> + return false;
>> + return true;
>> +}
>> +
>> struct mempolicy *__get_vma_policy(struct vm_area_struct *vma,
>> unsigned long addr)
>> {
>> --
>> 1.8.3.1
>>
>
>--
>Michal Hocko
>SUSE Labs
