[PATCH RFC -next 4/5] Docs/admin-guide/cgroup-v2: document upfront socket budget charging

[Cai Xinchen]

The "TCP socket buffers" entry in the memory.stat description leaves
the impression that the charge tracks in-flight packet buffers.
Since the budget-charging rework, a socket is instead charged its full
established memory budget (send buffer, receive buffer and
SO_RESERVE_MEM reservation) when the budget is created or resized, and
the charge is returned when the budget shrinks or the socket is
closed.  Say so.

Assisted-by: opencode:glm-5.3
Signed-off-by: Cai Xinchen <caixinchen1@xxxxxxxxxx>
---
 Documentation/admin-guide/cgroup-v2.rst | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 8d2603751c51..4f26a459cfdc 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -1309,7 +1309,11 @@ following types of memory usages are tracked.
 
 - Kernel data structures such as dentries and inodes.
 
-- TCP socket buffers.
+- TCP socket buffers. These are charged upfront for the socket's
+  established memory budget (send buffer, receive buffer and
+  SO_RESERVE_MEM reservation) when the budget is created or resized,
+  and returned when the budget shrinks or the socket is closed; the
+  charge is not tied to per-packet buffer usage.
 
 The above list may expand in the future for better coverage.
 
-- 
2.18.0.huawei.25