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b=Ii3HHFaP+cLRY1G6nl+4ikP+j0AuPQEmO39D9OK2MX5r11FixTJJu4FZ3CBiNVeEZ WVPF/ni06PFEfU+gLzl3vVmZ2j8E2/SncgOJ6iyKFabAVX+2L16QLJqsEw22X23u2f 2H6MDuPX3ALSchNr75SZhI7Zm82L+cTuuOb7wglYRCCi+FxQIG8Cw4GPEwIH9J5I9E VIoxuWl5har0rDJMMs7FL+xXcNmxrP7B19vLmS0pOivktsBwidprZjqqDElhDxtaLC AJBuEdqY7T+NjECJvRMG8eXMJqXPRd/K6RRUV3f/V9Ry0Pe1lS1d1FbZ+v8/61/CrA vQvyiJrp7LRSg== Date: Wed, 5 Aug 2026 17:26:35 +0100 From: "Lorenzo Stoakes (ARM)" To: =?utf-8?Q?C=C3=A9dric?= Le Goater Cc: Andrew Morton , linux-mm@kvack.org, Peter Xu , David Hildenbrand , Alex Williamson , Jason Gunthorpe , Zi Yan , stable@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/huge_memory: let special huge VMAs bypass the THP policy check Message-ID: References: <20260805055544.1568534-1-clg@redhat.com> <4ddc95f2-8868-4be3-9839-e2d14cf35fef@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4ddc95f2-8868-4be3-9839-e2d14cf35fef@redhat.com> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: CA4CAC000F X-Stat-Signature: qjhegi3ab3ymrttf3afs35i3umd5sj8z X-HE-Tag: 1785947213-979573 X-HE-Meta: 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 K+zL5eYV gMclNjIDem6+lHqEet1fBao9CG+QtKPjbmQcGWtsJH38vTUWSdFymM7wAdGxlt1FLk0RBox+cpjk3wcoXGGJBRuqnOWLdL9g1nbV7lSNoJvhZhZjOlPFiDWfrSg5y8Zlb5+EwwY6cypTZadlMhuABOImkMb/B/rta139fMkU66J7I7FLdXg/RpMe9p8Ee8DGSNQ079yMfq7cW3Y3vE4LBbVTDPeX6rRlznnbVIcWsk76XblUAkrkujcqeJPe7LI7DSQEbk+Vlj8PgRjnyMq3YgvOJTD33tuk1LdpO/03uaLc+1yvF6M7bnuXBAw+uZLI1nqjnWMqI5oKY3j3r6ax99MB1pEar7J1/1m1q Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Aug 05, 2026 at 06:21:30PM +0200, Cédric Le Goater wrote: > Thanks for the quick feedback Lorenzo ! > > So I think it should be something more like the attached. > > > > That way all the handling remains the same and the override is applied in > > the right place plus smaps keeps working. > > LGTM, do you want me to respin a v2 with what's below ? or you'd rather > send it yourself. Thanks, I think as it's somewhat divergent maybe better if I send it with Reported-by/Closes if that makes sense to you? I'd like to get David's input on it first however! > > C. > > > > > ----8<---- > > 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; > > +} > > + > > +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; > > > > /* > > -- > > 2.55.0 > > > -- Cheers, Lorenzo