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Wed, 08 Oct 2025 01:19:13 -0700 (PDT) MIME-Version: 1.0 References: <20250930055826.9810-1-laoar.shao@gmail.com> <20250930055826.9810-4-laoar.shao@gmail.com> <27e002e3-b39f-40f9-b095-52da0fbd0fc7@redhat.com> In-Reply-To: <27e002e3-b39f-40f9-b095-52da0fbd0fc7@redhat.com> From: Yafang Shao Date: Wed, 8 Oct 2025 16:18:37 +0800 X-Gm-Features: AS18NWBqVaYKWhKnTCEHPPwnoyf7n1_vwGYnsczH0QG6uK9Ydgy_AQN3Vgm1uv0 Message-ID: Subject: Re: [PATCH v9 mm-new 03/11] mm: thp: add support for BPF based THP order selection To: David Hildenbrand Cc: Alexei Starovoitov , Andrew Morton , ziy@nvidia.com, baolin.wang@linux.alibaba.com, Lorenzo Stoakes , Liam Howlett , npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, Johannes Weiner , usamaarif642@gmail.com, gutierrez.asier@huawei-partners.com, Matthew Wilcox , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Amery Hung , David Rientjes , Jonathan Corbet , 21cnbao@gmail.com, Shakeel Butt , Tejun Heo , lance.yang@linux.dev, Randy Dunlap , bpf , linux-mm , "open list:DOCUMENTATION" , LKML Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: rjyhb7d96pwy79fpm9mxp78s7xfkjcne X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 89E02140007 X-HE-Tag: 1759911554-902454 X-HE-Meta: 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 14A3BWZB 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Oct 8, 2025 at 4:08=E2=80=AFPM David Hildenbrand = wrote: > > On 03.10.25 04:18, Alexei Starovoitov wrote: > > On Mon, Sep 29, 2025 at 10:59=E2=80=AFPM Yafang Shao wrote: > >> > >> +unsigned long bpf_hook_thp_get_orders(struct vm_area_struct *vma, > >> + enum tva_type type, > >> + unsigned long orders) > >> +{ > >> + thp_order_fn_t *bpf_hook_thp_get_order; > >> + int bpf_order; > >> + > >> + /* No BPF program is attached */ > >> + if (!test_bit(TRANSPARENT_HUGEPAGE_BPF_ATTACHED, > >> + &transparent_hugepage_flags)) > >> + return orders; > >> + > >> + rcu_read_lock(); > >> + bpf_hook_thp_get_order =3D rcu_dereference(bpf_thp.thp_get_ord= er); > >> + if (WARN_ON_ONCE(!bpf_hook_thp_get_order)) > >> + goto out; > >> + > >> + bpf_order =3D bpf_hook_thp_get_order(vma, type, orders); > >> + orders &=3D BIT(bpf_order); > >> + > >> +out: > >> + rcu_read_unlock(); > >> + return orders; > >> +} > > > > I thought I explained it earlier. > > Nack to a single global prog approach. > > I agree. We should have the option to either specify a policy globally, > or more refined for cgroups/processes. > > It's an interesting question if a program would ever want to ship its > own policy: I can see use cases for that. > > So I agree that we should make it more flexible right from the start. To achieve per-process granularity, the struct-ops must be embedded within the mm_struct as follows: +#ifdef CONFIG_BPF_MM +struct bpf_mm_ops { +#ifdef CONFIG_BPF_THP + struct bpf_thp_ops bpf_thp; +#endif +}; +#endif + /* * Opaque type representing current mm_struct flag state. Must be accessed= via * mm_flags_xxx() helper functions. @@ -1268,6 +1281,10 @@ struct mm_struct { #ifdef CONFIG_MM_ID mm_id_t mm_id; #endif /* CONFIG_MM_ID */ + +#ifdef CONFIG_BPF_MM + struct bpf_mm_ops bpf_mm; +#endif } __randomize_layout; We should be aware that this will involve extensive changes in mm/. If we're aligned on this direction, I'll start working on the patches. --=20 Regards Yafang