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charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, Jul 28, 2025 at 4:03=E2=80=AFAM Pavel Begunkov wrote: > > From: Jakub Kicinski > > Document the semantics of the rx_buf_len ethtool ring param. > Clarify its meaning in case of HDS, where driver may have > two separate buffer pools. > > The various zero-copy TCP Rx schemes we have suffer from memory > management overhead. Specifically applications aren't too impressed > with the number of 4kB buffers they have to juggle. Zero-copy > TCP makes most sense with larger memory transfers so using > 16kB or 32kB buffers (with the help of HW-GRO) feels more > natural. > > Signed-off-by: Jakub Kicinski > Signed-off-by: Pavel Begunkov > --- > Documentation/networking/ethtool-netlink.rst | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/Documentation/networking/ethtool-netlink.rst b/Documentation= /networking/ethtool-netlink.rst > index b6e9af4d0f1b..eaa9c17a3cb1 100644 > --- a/Documentation/networking/ethtool-netlink.rst > +++ b/Documentation/networking/ethtool-netlink.rst > @@ -957,7 +957,6 @@ Kernel checks that requested ring sizes do not exceed= limits reported by > driver. Driver may impose additional constraints and may not support all > attributes. > > - > ``ETHTOOL_A_RINGS_CQE_SIZE`` specifies the completion queue event size. > Completion queue events (CQE) are the events posted by NIC to indicate t= he > completion status of a packet when the packet is sent (like send success= or > @@ -971,6 +970,11 @@ completion queue size can be adjusted in the driver = if CQE size is modified. > header / data split feature. If a received packet size is larger than th= is > threshold value, header and data will be split. > > +``ETHTOOL_A_RINGS_RX_BUF_LEN`` controls the size of the buffer chunks dr= iver > +uses to receive packets. If the device uses different memory polls for h= eaders pools, not polls. > +and payload this setting may control the size of the header buffers but = must > +control the size of the payload buffers. > + --=20 Thanks, Mina