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Fri, 14 Nov 2025 22:35:46 -0800 (PST) Received: from fedora ([172.59.161.218]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2a49da0662dsm19056274eec.2.2025.11.14.22.35.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 14 Nov 2025 22:35:46 -0800 (PST) From: Alex Tran To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, corbet@lwn.net Cc: martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, bpf@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Alex Tran Subject: [PATCH bpf-next v1] docs: bpf: map_array: specify BPF_MAP_TYPE_PERCPU_ARRAY value size limit Date: Fri, 14 Nov 2025 22:35:31 -0800 Message-ID: <20251115063531.2302903-1-alex.t.tran@gmail.com> X-Mailer: git-send-email 2.51.0 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" Specify value size limit for BPF_MAP_TYPE_PERCPU_ARRAY which is PCPU_MIN_UNIT_SIZE (32 kb). In percpu allocator (mm: percpu),=20 any request with a size greater than PCPU_MIN_UNIT_SIZE is rejected.=20 Signed-off-by: Alex Tran --- Documentation/bpf/map_array.rst | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/Documentation/bpf/map_array.rst b/Documentation/bpf/map_array.= rst index f2f51a53e8ae..fa56ff75190c 100644 --- a/Documentation/bpf/map_array.rst +++ b/Documentation/bpf/map_array.rst @@ -15,8 +15,9 @@ of constant size. The size of the array is defined in ``m= ax_entries`` at creation time. All array elements are pre-allocated and zero initialized w= hen created. ``BPF_MAP_TYPE_PERCPU_ARRAY`` uses a different memory region for = each CPU whereas ``BPF_MAP_TYPE_ARRAY`` uses the same memory region. The value -stored can be of any size, however, all array elements are aligned to 8 -bytes. +stored can be of any size for ``BPF_MAP_TYPE_ARRAY`` and not more than +``PCPU_MIN_UNIT_SIZE`` (32 kB) for ``BPF_MAP_TYPE_PERCPU_ARRAY``. All +array elements are aligned to 8 bytes. =20 Since kernel 5.5, memory mapping may be enabled for ``BPF_MAP_TYPE_ARRAY``= by setting the flag ``BPF_F_MMAPABLE``. The map definition is page-aligned and --=20 2.51.0