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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 8/6/26 18:19, David Hildenbrand (Arm) wrote: >> From d6537260722c8741586e6295c8eea68d06087efa Mon Sep 17 00:00:00 2001 >> From: "Lorenzo Stoakes (ARM)" >> Date: Wed, 5 Aug 2026 11:35:13 +0100 >> Subject: [PATCH] ideas >> >> --- >> mm/huge_memory.c | 32 +++++++++++++++++++++++++++++--- >> 1 file changed, 29 insertions(+), 3 deletions(-) >> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index abc65d608c23..5fa01364f089 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -111,6 +111,34 @@ static bool vma_is_special_huge(const struct vm_area_struct *vma) >> return vma_test_any(vma, VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT); >> } >> >> +static bool should_obey_thp_file_tunables(const struct vm_area_struct *vma, >> + bool forced_collapse) >> +{> + if (forced_collapse) >> + return false; >> + VM_WARN_ON_ONCE(vma_is_anonymous(vma)); >> + /* Huge PFN mappings allocate no folios so the policy doesn't apply. */ >> + if (vma_test(vma, VMA_PFNMAP_BIT) && vma->vm_ops->huge_fault) >> + return false; >> + return true; >> +} > > If that's sufficient, then this is is the better direction. > >> +> +static bool can_thp_collapse_file(const struct vm_area_struct *vma, >> + vm_flags_t vm_flags, bool forced_collapse) >> +{ >> + /* Override THP tunables? */ >> + if (!should_obey_thp_file_tunables(vma, forced_collapse)) >> + return true; >> + /* THP=always? */ >> + if (hugepage_global_always()) >> + return true; >> + /* THP=madvise? */ >> + if (!hugepage_global_enabled()) >> + return false; >> + /* Has VMA had madvise(..., MADV_HUGEPAGE) applied to it? */ >> + return vm_flags & VM_HUGEPAGE; >> +} >> + >> unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma, >> vm_flags_t vm_flags, >> enum tva_type type, >> @@ -188,9 +216,7 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma, >> * Enforce THP collapse requirements as necessary. Anonymous vmas >> * were already handled in thp_vma_allowable_orders(). >> */ >> - if (!forced_collapse && >> - (!hugepage_global_enabled() || (!(vm_flags & VM_HUGEPAGE) && >> - !hugepage_global_always()))) >> + if (!can_thp_collapse_file(vma, vm_flags, forced_collapse)) >> return 0; > > I played a bit with that and came up with the following. Not quite happy about > it, just for your inspiration on naming and what to split out. > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index a00df56a68b57..8ba77608959d4 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -111,6 +111,54 @@ static bool vma_is_special_huge(const struct vm_area_struct > *vma) > return vma_test_any(vma, VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT); > } > > +static bool file_vma_honors_thp_toggles(struct vm_area_struct *vma,> + enum tva_type type) > +{ > + const bool forced_collapse = type == TVA_FORCED_COLLAPSE; > + > + if (forced_collapse) > + return false; > + /* Huge PFN mappings allocate no folios so the policy doesn't apply. */ So, may be rename the routine to file_vma_thp_policy_applies() ? > + return !(vma_test(vma, VMA_PFNMAP_BIT) && vma->vm_ops->huge_fault); > +} > + > +static bool vma_thp_toggles_enabled(struct vm_area_struct *vma, This routine could use the same 'file_vma_' prefix. > + vm_flags_t vm_flags) > +{ > + /* THP=always? */ > + if (hugepage_global_always()) > + return true; > + /* THP=madvise and actually advised? */ > + return hugepage_global_enabled() && vm_flags & VM_HUGEPAGE; I would add extra parentheses around 'vm_flags & VM_HUGEPAGE' > +} > + > +static bool file_vma_forces_order_0(struct vm_area_struct *vma, > + vm_flags_t vm_flags, enum tva_type type) > +{ > + const bool in_pf = type == TVA_PAGEFAULT; > + const bool smaps = type == TVA_SMAPS; > + > + /* > + * Enforce THP collapse requirements as necessary. Anonymous vmas > + * were already handled in thp_vma_allowable_orders(). > + */ > + > + if (file_vma_honors_thp_toggles(vma, type) && > + !vma_thp_toggles_enabled(vma, vm_flags)) > + return true; > + > + /* > + * Trust that ->huge_fault() handlers know what they are doing > + * in fault path. > + */ > + if (((in_pf || smaps)) && vma->vm_ops->huge_fault) and there remove the extra parentheses. > + return false; > + /* Only regular file is valid in collapse path */ > + if (((!in_pf || smaps)) && file_thp_enabled(vma)) there too. Thanks, C. > + return false; > + return true; > +} > + > unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma, > vm_flags_t vm_flags, > enum tva_type type, > @@ -183,27 +231,8 @@ unsigned long __thp_vma_allowable_orders(struct > vm_area_struct *vma, > vma, vma_start_pgoff(vma), 0, > forced_collapse); > > - if (!vma_is_anonymous(vma)) { > - /* > - * Enforce THP collapse requirements as necessary. Anonymous vmas > - * were already handled in thp_vma_allowable_orders(). > - */ > - if (!forced_collapse && > - (!hugepage_global_enabled() || (!(vm_flags & VM_HUGEPAGE) && > - !hugepage_global_always()))) > - return 0; > - > - /* > - * Trust that ->huge_fault() handlers know what they are doing > - * in fault path. > - */ > - if (((in_pf || smaps)) && vma->vm_ops->huge_fault) > - return orders; > - /* Only regular file is valid in collapse path */ > - if (((!in_pf || smaps)) && file_thp_enabled(vma)) > - return orders; > - return 0; > - } > + if (!vma_is_anonymous(vma)) > + return __file_vma_forces_order_0(vma, vm_flags, type) ? 0 : orders; > > if (vma_is_temporary_stack(vma)) > return 0; >