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Fri, 26 Sep 2025 02:35:24 -0700 (PDT) From: Yafang Shao To: akpm@linux-foundation.org, david@redhat.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, hannes@cmpxchg.org, usamaarif642@gmail.com, gutierrez.asier@huawei-partners.com, willy@infradead.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, ameryhung@gmail.com, rientjes@google.com, corbet@lwn.net, 21cnbao@gmail.com, shakeel.butt@linux.dev, tj@kernel.org, lance.yang@linux.dev Cc: bpf@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Yafang Shao Subject: [PATCH v8 mm-new 12/12] Documentation: add BPF-based THP policy management Date: Fri, 26 Sep 2025 17:33:43 +0800 Message-Id: <20250926093343.1000-13-laoar.shao@gmail.com> X-Mailer: git-send-email 2.37.1 (Apple Git-137.1) In-Reply-To: <20250926093343.1000-1-laoar.shao@gmail.com> References: <20250926093343.1000-1-laoar.shao@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add the documentation. Signed-off-by: Yafang Shao --- Documentation/admin-guide/mm/transhuge.rst | 39 ++++++++++++++++++++++ 1 file changed, 39 insertions(+) diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/adm= in-guide/mm/transhuge.rst index 1654211cc6cf..fa03bcdb8854 100644 --- a/Documentation/admin-guide/mm/transhuge.rst +++ b/Documentation/admin-guide/mm/transhuge.rst @@ -738,3 +738,42 @@ support enabled just fine as always. No difference can= be noted in hugetlbfs other than there will be less overall fragmentation. All usual features belonging to hugetlbfs are preserved and unaffected. libhugetlbfs will also work fine as usual. + +BPF-based THP adjustment +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +Overview +-------- + +When the system is configured with "always" or "madvise" THP mode, a BPF p= rogram +can be used to adjust THP allocation policies dynamically. This enables +fine-grained control over THP decisions based on various factors including +workload identity, allocation context, and system memory pressure. + +Program Interface +----------------- + +This feature implements a struct_ops BPF program with the following interf= ace:: + + int thp_get_order(struct vm_area_struct *vma, + enum tva_type type, + unsigned long orders); + +Parameters:: + + @vma: vm_area_struct associated with the THP allocation + @type: TVA type for current @vma + @orders: Bitmask of available THP orders for this allocation + +Return value:: + + The suggested THP order for allocation from the BPF program. Must be + a valid, available order. + +Implementation Notes +-------------------- + +This is currently an experimental feature. +CONFIG_BPF_THP_GET_ORDER_EXPERIMENTAL must be enabled to use it. +Only one BPF program can be attached at a time, but the program can be upd= ated +dynamically to adjust policies without requiring affected tasks to be rest= arted. --=20 2.47.3