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authorShay Agroskin <shayagr@amazon.com>2023-03-23 19:36:05 +0300
committerJakub Kicinski <kuba@kernel.org>2023-03-28 05:49:58 +0300
commit233eb4e786b57ea686b51c13a04cc2839fd682fc (patch)
tree7775d4a7c08243c24b1afabe7f6254be88f6e3a3 /Documentation/networking
parent3e4d5ba9a3f85f21f1ebdee5a5901bb43389abc5 (diff)
downloadlinux-233eb4e786b57ea686b51c13a04cc2839fd682fc.tar.xz
ethtool: Add support for configuring tx_push_buf_len
This attribute, which is part of ethtool's ring param configuration allows the user to specify the maximum number of the packet's payload that can be written directly to the device. Example usage: # ethtool -G [interface] tx-push-buf-len [number of bytes] Co-developed-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Shay Agroskin <shayagr@amazon.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'Documentation/networking')
-rw-r--r--Documentation/networking/ethtool-netlink.rst47
1 files changed, 31 insertions, 16 deletions
diff --git a/Documentation/networking/ethtool-netlink.rst b/Documentation/networking/ethtool-netlink.rst
index e1bc6186d7ea..cd0973d4ba01 100644
--- a/Documentation/networking/ethtool-netlink.rst
+++ b/Documentation/networking/ethtool-netlink.rst
@@ -860,22 +860,24 @@ Request contents:
Kernel response contents:
- ==================================== ====== ===========================
- ``ETHTOOL_A_RINGS_HEADER`` nested reply header
- ``ETHTOOL_A_RINGS_RX_MAX`` u32 max size of RX ring
- ``ETHTOOL_A_RINGS_RX_MINI_MAX`` u32 max size of RX mini ring
- ``ETHTOOL_A_RINGS_RX_JUMBO_MAX`` u32 max size of RX jumbo ring
- ``ETHTOOL_A_RINGS_TX_MAX`` u32 max size of TX ring
- ``ETHTOOL_A_RINGS_RX`` u32 size of RX ring
- ``ETHTOOL_A_RINGS_RX_MINI`` u32 size of RX mini ring
- ``ETHTOOL_A_RINGS_RX_JUMBO`` u32 size of RX jumbo ring
- ``ETHTOOL_A_RINGS_TX`` u32 size of TX ring
- ``ETHTOOL_A_RINGS_RX_BUF_LEN`` u32 size of buffers on the ring
- ``ETHTOOL_A_RINGS_TCP_DATA_SPLIT`` u8 TCP header / data split
- ``ETHTOOL_A_RINGS_CQE_SIZE`` u32 Size of TX/RX CQE
- ``ETHTOOL_A_RINGS_TX_PUSH`` u8 flag of TX Push mode
- ``ETHTOOL_A_RINGS_RX_PUSH`` u8 flag of RX Push mode
- ==================================== ====== ===========================
+ ======================================= ====== ===========================
+ ``ETHTOOL_A_RINGS_HEADER`` nested reply header
+ ``ETHTOOL_A_RINGS_RX_MAX`` u32 max size of RX ring
+ ``ETHTOOL_A_RINGS_RX_MINI_MAX`` u32 max size of RX mini ring
+ ``ETHTOOL_A_RINGS_RX_JUMBO_MAX`` u32 max size of RX jumbo ring
+ ``ETHTOOL_A_RINGS_TX_MAX`` u32 max size of TX ring
+ ``ETHTOOL_A_RINGS_RX`` u32 size of RX ring
+ ``ETHTOOL_A_RINGS_RX_MINI`` u32 size of RX mini ring
+ ``ETHTOOL_A_RINGS_RX_JUMBO`` u32 size of RX jumbo ring
+ ``ETHTOOL_A_RINGS_TX`` u32 size of TX ring
+ ``ETHTOOL_A_RINGS_RX_BUF_LEN`` u32 size of buffers on the ring
+ ``ETHTOOL_A_RINGS_TCP_DATA_SPLIT`` u8 TCP header / data split
+ ``ETHTOOL_A_RINGS_CQE_SIZE`` u32 Size of TX/RX CQE
+ ``ETHTOOL_A_RINGS_TX_PUSH`` u8 flag of TX Push mode
+ ``ETHTOOL_A_RINGS_RX_PUSH`` u8 flag of RX Push mode
+ ``ETHTOOL_A_RINGS_TX_PUSH_BUF_LEN`` u32 size of TX push buffer
+ ``ETHTOOL_A_RINGS_TX_PUSH_BUF_LEN_MAX`` u32 max size of TX push buffer
+ ======================================= ====== ===========================
``ETHTOOL_A_RINGS_TCP_DATA_SPLIT`` indicates whether the device is usable with
page-flipping TCP zero-copy receive (``getsockopt(TCP_ZEROCOPY_RECEIVE)``).
@@ -891,6 +893,18 @@ through MMIO writes, thus reducing the latency. However, enabling this feature
may increase the CPU cost. Drivers may enforce additional per-packet
eligibility checks (e.g. on packet size).
+``ETHTOOL_A_RINGS_TX_PUSH_BUF_LEN`` specifies the maximum number of bytes of a
+transmitted packet a driver can push directly to the underlying device
+('push' mode). Pushing some of the payload bytes to the device has the
+advantages of reducing latency for small packets by avoiding DMA mapping (same
+as ``ETHTOOL_A_RINGS_TX_PUSH`` parameter) as well as allowing the underlying
+device to process packet headers ahead of fetching its payload.
+This can help the device to make fast actions based on the packet's headers.
+This is similar to the "tx-copybreak" parameter, which copies the packet to a
+preallocated DMA memory area instead of mapping new memory. However,
+tx-push-buff parameter copies the packet directly to the device to allow the
+device to take faster actions on the packet.
+
RINGS_SET
=========
@@ -908,6 +922,7 @@ Request contents:
``ETHTOOL_A_RINGS_CQE_SIZE`` u32 Size of TX/RX CQE
``ETHTOOL_A_RINGS_TX_PUSH`` u8 flag of TX Push mode
``ETHTOOL_A_RINGS_RX_PUSH`` u8 flag of RX Push mode
+ ``ETHTOOL_A_RINGS_TX_PUSH_BUF_LEN`` u32 size of TX push buffer
==================================== ====== ===========================
Kernel checks that requested ring sizes do not exceed limits reported by