Re: [PATCH net-next 1/3] net: ethtool: extend ringparam set/get APIs for tx_push

[wangjie (L)]

On 2022/4/9 5:55, Jakub Kicinski wrote:
> On Fri, 8 Apr 2022 15:12:43 +0800 Guangbin Huang wrote:
> > From: Jie Wang <wangjie125@xxxxxxxxxx>
> >
> > Currently tx push is a standard driver feature which controls use of a fast
> > path descriptor push. So this patch extends the ringparam APIs and data
> > structures to support set/get tx push by ethtool -G/g.
> >
> > Signed-off-by: Jie Wang <wangjie125@xxxxxxxxxx>
> > Signed-off-by: Guangbin Huang <huangguangbin2@xxxxxxxxxx>
>
> > +``ETHTOOL_A_RINGS_TX_PUSH`` flag is used to choose the ordinary path or the fast
> > +path to send packets. In ordinary path, driver fills BDs to DDR memory and
> > +notifies NIC hardware. In fast path, driver pushes BDs to the device memory
> > +directly and thus reducing the sending latencies. Setting tx push attribute "on"
> > +will enable tx push mode and send packets in fast path if packet size matches.
> > +For those not supported hardwares, this attributes is "off" by default settings.
>
> Since you need to respin to fix the kdoc warning - could you also add
> a mention that enabling this feature may increase CPU cost? Unless it's
> not the case for your implementation, I thought it usually is..
ok, i will add it in v2
> >  RINGS_SET
> >  =========
> > @@ -887,6 +894,7 @@ Request contents:
> >    ``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_CQE_SIZE``          u32     Size of TX/RX CQE
> > +  ``ETHTOOL_A_RINGS_TX_PUSH``           u8      flag of TX Push mode
> >    ====================================  ======  ===========================
> >
> >  Kernel checks that requested ring sizes do not exceed limits reported by
> > diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
> > index 4af58459a1e7..ede4f9154cd2 100644
> > --- a/include/linux/ethtool.h
> > +++ b/include/linux/ethtool.h
> > @@ -71,11 +71,13 @@ enum {
> >   * struct kernel_ethtool_ringparam - RX/TX ring configuration
> >   * @rx_buf_len: Current length of buffers on the rx ring.
> >   * @tcp_data_split: Scatter packet headers and data to separate buffers
> > + * @tx_push: The flag of tx push mode
> >   * @cqe_size: Size of TX/RX completion queue event
> >   */
> >  struct kernel_ethtool_ringparam {
> >  	u32	rx_buf_len;
> >  	u8	tcp_data_split;
> > +	u8	tx_push;
> >  	u32	cqe_size;
> >  };
> >
> > @@ -87,6 +89,7 @@ struct kernel_ethtool_ringparam {
> >  enum ethtool_supported_ring_param {
> >  	ETHTOOL_RING_USE_RX_BUF_LEN = BIT(0),
> >  	ETHTOOL_RING_USE_CQE_SIZE   = BIT(1),
> > +	ETHTOOL_RING_USE_TX_PUSH    = BIT(2),
>
> include/linux/ethtool.h:94: warning: Enum value 'ETHTOOL_RING_USE_TX_PUSH' not described in enum 'ethtool_supported_ring_param'
thx, I will fix it in v2
> .