linux-kernel - [PATCH bpf-next v1] docs: bpf: map_array: specify BPF_MAP_TYPE_PERCPU

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Message-ID: <20251115063531.2302903-1-alex.t.tran@gmail.com>
Date: Fri, 14 Nov 2025 22:35:31 -0800
From: Alex Tran <alex.t.tran@...il.com>
To: ast@...nel.org,
	daniel@...earbox.net,
	andrii@...nel.org,
	corbet@....net
Cc: martin.lau@...ux.dev,
	eddyz87@...il.com,
	song@...nel.org,
	yonghong.song@...ux.dev,
	john.fastabend@...il.com,
	kpsingh@...nel.org,
	sdf@...ichev.me,
	haoluo@...gle.com,
	jolsa@...nel.org,
	bpf@...r.kernel.org,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Alex Tran <alex.t.tran@...il.com>
Subject: [PATCH bpf-next v1] docs: bpf: map_array: specify BPF_MAP_TYPE_PERCPU_ARRAY value size limit

Specify value size limit for BPF_MAP_TYPE_PERCPU_ARRAY which
is PCPU_MIN_UNIT_SIZE (32 kb). In percpu allocator (mm: percpu), 
any request with a size greater than PCPU_MIN_UNIT_SIZE is rejected. 

Signed-off-by: Alex Tran <alex.t.tran@...il.com>
---
 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 ``max_entries`` at
 creation time. All array elements are pre-allocated and zero initialized when
 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.
 
 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
-- 
2.51.0