[PATCH v2 net-next 02/21] net: Introduce direct data placement tcp offload

Eric Dumazet edumazet at google.com
Thu Jan 14 10:57:32 EST 2021


On Thu, Jan 14, 2021 at 4:10 PM Boris Pismenny <borisp at mellanox.com> wrote:
>
> This commit introduces direct data placement offload for TCP.
> This capability is accompanied by new net_device operations that
> configure hardware contexts. There is a context per socket, and a context per DDP
> opreation. Additionally, a resynchronization routine is used to assist
> hardware handle TCP OOO, and continue the offload.
> Furthermore, we let the offloading driver advertise what is the max hw
> sectors/segments.
>
> Using this interface, the NIC hardware will scatter TCP payload directly
> to the BIO pages according to the command_id.
> To maintain the correctness of the network stack, the driver is expected
> to construct SKBs that point to the BIO pages.
>
> This, the SKB represents the data on the wire, while it is pointing
> to data that is already placed in the destination buffer.
> As a result, data from page frags should not be copied out to
> the linear part.
>
> As SKBs that use DDP are already very memory efficient, we modify
> skb_condence to avoid copying data from fragments to the linear
> part of SKBs that belong to a socket that uses DDP offload.
>
> A follow-up patch will use this interface for DDP in NVMe-TCP.
>
> Signed-off-by: Boris Pismenny <borisp at mellanox.com>
> Signed-off-by: Ben Ben-Ishay <benishay at mellanox.com>
> Signed-off-by: Or Gerlitz <ogerlitz at mellanox.com>
> Signed-off-by: Yoray Zack <yorayz at mellanox.com>
> ---
>  include/linux/netdev_features.h    |   2 +
>  include/linux/netdevice.h          |   5 ++
>  include/net/inet_connection_sock.h |   4 +
>  include/net/tcp_ddp.h              | 136 +++++++++++++++++++++++++++++
>  net/Kconfig                        |   9 ++
>  net/core/skbuff.c                  |   9 +-
>  net/ethtool/common.c               |   1 +
>  7 files changed, 165 insertions(+), 1 deletion(-)
>  create mode 100644 include/net/tcp_ddp.h
>
> diff --git a/include/linux/netdev_features.h b/include/linux/netdev_features.h
> index 934de56644e7..fb35dcac03d2 100644
> --- a/include/linux/netdev_features.h
> +++ b/include/linux/netdev_features.h
> @@ -84,6 +84,7 @@ enum {
>         NETIF_F_GRO_FRAGLIST_BIT,       /* Fraglist GRO */
>
>         NETIF_F_HW_MACSEC_BIT,          /* Offload MACsec operations */
> +       NETIF_F_HW_TCP_DDP_BIT,         /* TCP direct data placement offload */
>
>         /*
>          * Add your fresh new feature above and remember to update
> @@ -157,6 +158,7 @@ enum {
>  #define NETIF_F_GRO_FRAGLIST   __NETIF_F(GRO_FRAGLIST)
>  #define NETIF_F_GSO_FRAGLIST   __NETIF_F(GSO_FRAGLIST)
>  #define NETIF_F_HW_MACSEC      __NETIF_F(HW_MACSEC)
> +#define NETIF_F_HW_TCP_DDP     __NETIF_F(HW_TCP_DDP)
>
>  /* Finds the next feature with the highest number of the range of start till 0.
>   */
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 259be67644e3..3dd3cdf5dec3 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -941,6 +941,7 @@ struct dev_ifalias {
>
>  struct devlink;
>  struct tlsdev_ops;
> +struct tcp_ddp_dev_ops;
>
>  struct netdev_name_node {
>         struct hlist_node hlist;
> @@ -1937,6 +1938,10 @@ struct net_device {
>         const struct tlsdev_ops *tlsdev_ops;
>  #endif
>
> +#ifdef CONFIG_TCP_DDP
> +       const struct tcp_ddp_dev_ops *tcp_ddp_ops;
> +#endif
> +
>         const struct header_ops *header_ops;
>
>         unsigned int            flags;
> diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
> index 7338b3865a2a..a08b85b53aa8 100644
> --- a/include/net/inet_connection_sock.h
> +++ b/include/net/inet_connection_sock.h
> @@ -66,6 +66,8 @@ struct inet_connection_sock_af_ops {
>   * @icsk_ulp_ops          Pluggable ULP control hook
>   * @icsk_ulp_data         ULP private data
>   * @icsk_clean_acked      Clean acked data hook
> + * @icsk_ulp_ddp_ops      Pluggable ULP direct data placement control hook
> + * @icsk_ulp_ddp_data     ULP direct data placement private data
>   * @icsk_listen_portaddr_node  hash to the portaddr listener hashtable
>   * @icsk_ca_state:        Congestion control state
>   * @icsk_retransmits:     Number of unrecovered [RTO] timeouts
> @@ -94,6 +96,8 @@ struct inet_connection_sock {
>         const struct tcp_ulp_ops  *icsk_ulp_ops;
>         void __rcu                *icsk_ulp_data;
>         void (*icsk_clean_acked)(struct sock *sk, u32 acked_seq);

#ifdef CONFIG_TCP_DDP ?

> +       const struct tcp_ddp_ulp_ops  *icsk_ulp_ddp_ops;
> +       void __rcu                *icsk_ulp_ddp_data;
>         struct hlist_node         icsk_listen_portaddr_node;
>         unsigned int              (*icsk_sync_mss)(struct sock *sk, u32 pmtu);
>         __u8                      icsk_ca_state:5,
> diff --git a/include/net/tcp_ddp.h b/include/net/tcp_ddp.h
> new file mode 100644
> index 000000000000..31e5b1a16d0f
> --- /dev/null
> +++ b/include/net/tcp_ddp.h
> @@ -0,0 +1,136 @@
> +/* SPDX-License-Identifier: GPL-2.0
> + *
> + * tcp_ddp.h
> + *     Author: Boris Pismenny <borisp at mellanox.com>
> + *     Copyright (C) 2021 Mellanox Technologies.
> + */
> +#ifndef _TCP_DDP_H
> +#define _TCP_DDP_H
> +
> +#include <linux/netdevice.h>
> +#include <net/inet_connection_sock.h>
> +#include <net/sock.h>
> +
> +/* limits returned by the offload driver, zero means don't care */
> +struct tcp_ddp_limits {
> +       int      max_ddp_sgl_len;
> +};
> +
> +enum tcp_ddp_type {
> +       TCP_DDP_NVME = 1,
> +};
> +
> +/**
> + * struct tcp_ddp_config - Generic tcp ddp configuration: tcp ddp IO queue
> + * config implementations must use this as the first member.
> + * Add new instances of tcp_ddp_config below (nvme-tcp, etc.).
> + */
> +struct tcp_ddp_config {
> +       enum tcp_ddp_type    type;
> +       unsigned char        buf[];
> +};
> +
> +/**
> + * struct nvme_tcp_ddp_config - nvme tcp ddp configuration for an IO queue
> + *
> + * @pfv:        pdu version (e.g., NVME_TCP_PFV_1_0)
> + * @cpda:       controller pdu data alignmend (dwords, 0's based)
> + * @dgst:       digest types enabled.
> + *              The netdev will offload crc if ddp_crc is supported.
> + * @queue_size: number of nvme-tcp IO queue elements
> + * @queue_id:   queue identifier
> + * @cpu_io:     cpu core running the IO thread for this queue
> + */
> +struct nvme_tcp_ddp_config {
> +       struct tcp_ddp_config   cfg;
> +
> +       u16                     pfv;
> +       u8                      cpda;
> +       u8                      dgst;
> +       int                     queue_size;
> +       int                     queue_id;
> +       int                     io_cpu;
> +};
> +
> +/**
> + * struct tcp_ddp_io - tcp ddp configuration for an IO request.
> + *
> + * @command_id:  identifier on the wire associated with these buffers
> + * @nents:       number of entries in the sg_table
> + * @sg_table:    describing the buffers for this IO request
> + * @first_sgl:   first SGL in sg_table
> + */
> +struct tcp_ddp_io {
> +       u32                     command_id;
> +       int                     nents;
> +       struct sg_table         sg_table;
> +       struct scatterlist      first_sgl[SG_CHUNK_SIZE];
> +};
> +
> +/* struct tcp_ddp_dev_ops - operations used by an upper layer protocol to configure ddp offload
> + *
> + * @tcp_ddp_limits:    limit the number of scatter gather entries per IO.
> + *                     the device driver can use this to limit the resources allocated per queue.
> + * @tcp_ddp_sk_add:    add offload for the queue represennted by the socket+config pair.
> + *                     this function is used to configure either copy, crc or both offloads.
> + * @tcp_ddp_sk_del:    remove offload from the socket, and release any device related resources.
> + * @tcp_ddp_setup:     request copy offload for buffers associated with a command_id in tcp_ddp_io.
> + * @tcp_ddp_teardown:  release offload resources association between buffers and command_id in
> + *                     tcp_ddp_io.
> + * @tcp_ddp_resync:    respond to the driver's resync_request. Called only if resync is successful.
> + */
> +struct tcp_ddp_dev_ops {
> +       int (*tcp_ddp_limits)(struct net_device *netdev,
> +                             struct tcp_ddp_limits *limits);
> +       int (*tcp_ddp_sk_add)(struct net_device *netdev,
> +                             struct sock *sk,
> +                             struct tcp_ddp_config *config);
> +       void (*tcp_ddp_sk_del)(struct net_device *netdev,
> +                              struct sock *sk);
> +       int (*tcp_ddp_setup)(struct net_device *netdev,
> +                            struct sock *sk,
> +                            struct tcp_ddp_io *io);
> +       int (*tcp_ddp_teardown)(struct net_device *netdev,
> +                               struct sock *sk,
> +                               struct tcp_ddp_io *io,
> +                               void *ddp_ctx);
> +       void (*tcp_ddp_resync)(struct net_device *netdev,
> +                              struct sock *sk, u32 seq);
> +};
> +
> +#define TCP_DDP_RESYNC_REQ BIT(0)
> +
> +/**
> + * struct tcp_ddp_ulp_ops - Interface to register uppper layer Direct Data Placement (DDP) TCP offload
> + */
> +struct tcp_ddp_ulp_ops {
> +       /* NIC requests ulp to indicate if @seq is the start of a message */
> +       bool (*resync_request)(struct sock *sk, u32 seq, u32 flags);
> +       /* NIC driver informs the ulp that ddp teardown is done - used for async completions*/
> +       void (*ddp_teardown_done)(void *ddp_ctx);
> +};
> +
> +/**
> + * struct tcp_ddp_ctx - Generic tcp ddp context: device driver per queue contexts must
> + * use this as the first member.
> + */
> +struct tcp_ddp_ctx {
> +       enum tcp_ddp_type    type;
> +       unsigned char        buf[];
> +};
> +
> +static inline struct tcp_ddp_ctx *tcp_ddp_get_ctx(const struct sock *sk)
> +{
> +       struct inet_connection_sock *icsk = inet_csk(sk);
> +
> +       return (__force struct tcp_ddp_ctx *)icsk->icsk_ulp_ddp_data;
> +}
> +
> +static inline void tcp_ddp_set_ctx(struct sock *sk, void *ctx)
> +{
> +       struct inet_connection_sock *icsk = inet_csk(sk);
> +
> +       rcu_assign_pointer(icsk->icsk_ulp_ddp_data, ctx);
> +}
> +
> +#endif //_TCP_DDP_H
> diff --git a/net/Kconfig b/net/Kconfig
> index f4c32d982af6..3876861cdc90 100644
> --- a/net/Kconfig
> +++ b/net/Kconfig
> @@ -457,6 +457,15 @@ config ETHTOOL_NETLINK
>           netlink. It provides better extensibility and some new features,
>           e.g. notification messages.
>
> +config TCP_DDP
> +       bool "TCP direct data placement offload"
> +       default n
> +       help
> +         Direct Data Placement (DDP) offload for TCP enables ULP, such as
> +         NVMe-TCP/iSCSI, to request the NIC to place TCP payload data
> +         of a command response directly into kernel pages.
> +
> +
>  endif   # if NET
>
>  # Used by archs to tell that they support BPF JIT compiler plus which flavour.
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index f62cae3f75d8..791c1b6bc067 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -69,6 +69,7 @@
>  #include <net/xfrm.h>
>  #include <net/mpls.h>
>  #include <net/mptcp.h>
> +#include <net/tcp_ddp.h>
>
>  #include <linux/uaccess.h>
>  #include <trace/events/skb.h>
> @@ -6140,9 +6141,15 @@ EXPORT_SYMBOL(pskb_extract);
>   */
>  void skb_condense(struct sk_buff *skb)
>  {
> +       bool is_ddp = false;
> +
> +#ifdef CONFIG_TCP_DDP

This looks strange to me : TCP should call this helper while skb->sk is NULL

Are you sure this is not dead code ?

> +       is_ddp = skb->sk && inet_csk(skb->sk) &&
> +                inet_csk(skb->sk)->icsk_ulp_ddp_data;
> +#endif
>         if (skb->data_len) {
>                 if (skb->data_len > skb->end - skb->tail ||
> -                   skb_cloned(skb))
> +                   skb_cloned(skb) || is_ddp)
>                         return;
>
>                 /* Nice, we can free page frag(s) right now */
> diff --git a/net/ethtool/common.c b/net/ethtool/common.c
> index 24036e3055a1..a2ff7a4a6bbf 100644
> --- a/net/ethtool/common.c
> +++ b/net/ethtool/common.c
> @@ -68,6 +68,7 @@ const char netdev_features_strings[NETDEV_FEATURE_COUNT][ETH_GSTRING_LEN] = {
>         [NETIF_F_HW_TLS_RX_BIT] =        "tls-hw-rx-offload",
>         [NETIF_F_GRO_FRAGLIST_BIT] =     "rx-gro-list",
>         [NETIF_F_HW_MACSEC_BIT] =        "macsec-hw-offload",
> +       [NETIF_F_HW_TCP_DDP_BIT] =       "tcp-ddp-offload",
>  };
>
>  const char
> --
> 2.24.1
>



More information about the Linux-nvme mailing list