Messages in this thread | | | Subject | Re: [PATCH 3/3] mm,thp,shmem: make khugepaged obey tmpfs mount flags | From | Vlastimil Babka <> | Date | Thu, 26 Nov 2020 18:18:29 +0100 |
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On 11/24/20 8:49 PM, Rik van Riel wrote: > Currently if thp enabled=[madvise], mounting a tmpfs filesystem > with huge=always and mmapping files from that tmpfs does not > result in khugepaged collapsing those mappings, despite the > mount flag indicating that it should. > > Fix that by breaking up the blocks of tests in hugepage_vma_check > a little bit, and testing things in the correct order. > > Signed-off-by: Rik van Riel <riel@surriel.com> > Fixes: c2231020ea7b ("mm: thp: register mm for khugepaged when merging vma for shmem")
Looks ok. But, it we have sysfs thp enabled=never, and shmem mount explicitly thp enabled, then shmem mount overrides the global sysfs setting and thp's will be allocated there, right? However, khugepaged_enabled() will be false and thus khugepaged won't run at all? So a similar situation than what you're fixing here.
> --- > include/linux/khugepaged.h | 2 ++ > mm/khugepaged.c | 22 ++++++++++++++++------ > 2 files changed, 18 insertions(+), 6 deletions(-) > > diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h > index c941b7377321..2fcc01891b47 100644 > --- a/include/linux/khugepaged.h > +++ b/include/linux/khugepaged.h > @@ -3,6 +3,7 @@ > #define _LINUX_KHUGEPAGED_H > > #include <linux/sched/coredump.h> /* MMF_VM_HUGEPAGE */ > +#include <linux/shmem_fs.h> > > > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > @@ -57,6 +58,7 @@ static inline int khugepaged_enter(struct vm_area_struct *vma, > { > if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags)) > if ((khugepaged_always() || > + (shmem_file(vma->vm_file) && shmem_huge_enabled(vma)) || > (khugepaged_req_madv() && (vm_flags & VM_HUGEPAGE))) && > !(vm_flags & VM_NOHUGEPAGE) && > !test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 4e3dff13eb70..abab394c4206 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -440,18 +440,28 @@ static inline int khugepaged_test_exit(struct mm_struct *mm) > static bool hugepage_vma_check(struct vm_area_struct *vma, > unsigned long vm_flags) > { > - if ((!(vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || > - (vm_flags & VM_NOHUGEPAGE) || > + /* Explicitly disabled through madvise. */ > + if ((vm_flags & VM_NOHUGEPAGE) || > test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) > return false; > > - if (shmem_file(vma->vm_file) || > - (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && > - vma->vm_file && > - (vm_flags & VM_DENYWRITE))) { > + /* Enabled via shmem mount options or sysfs settings. */ > + if (shmem_file(vma->vm_file) && shmem_huge_enabled(vma)) { > return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, > HPAGE_PMD_NR); > } > + > + /* THP settings require madvise. */ > + if (!(vm_flags & VM_HUGEPAGE) && !khugepaged_always()) > + return false; > + > + /* Read-only file mappings need to be aligned for THP to work. */ > + if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && vma->vm_file && > + (vm_flags & VM_DENYWRITE)) { > + return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, > + HPAGE_PMD_NR); > + } > + > if (!vma->anon_vma || vma->vm_ops) > return false; > if (vma_is_temporary_stack(vma)) >
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