On 9/30/20 9:20 AM, Boris Pismenny wrote:
This commit introduces direct data placement offload to NVME
TCP. There is a context per queue, which is established after the
handshake
using the tcp_ddp_sk_add/del NDOs.
Additionally, a resynchronization routine is used to assist
hardware recovery from TCP OOO, and continue the offload.
Resynchronization operates as follows:
1. TCP OOO causes the NIC HW to stop the offload
2. NIC HW identifies a PDU header at some TCP sequence number,
and asks NVMe-TCP to confirm it.
This request is delivered from the NIC driver to NVMe-TCP by first
finding the socket for the packet that triggered the request, and
then fiding the nvme_tcp_queue that is used by this routine.
Finally, the request is recorded in the nvme_tcp_queue.
3. When NVMe-TCP observes the requested TCP sequence, it will compare
it with the PDU header TCP sequence, and report the result to the
NIC driver (tcp_ddp_resync), which will update the HW,
and resume offload when all is successful.
Furthermore, we let the offloading driver advertise what is the max hw
sectors/segments via tcp_ddp_limits.
A follow-up patch introduces the data-path changes required for this
offload.
Signed-off-by: Boris Pismenny <bor...@mellanox.com>
Signed-off-by: Ben Ben-Ishay <benis...@mellanox.com>
Signed-off-by: Or Gerlitz <ogerl...@mellanox.com>
Signed-off-by: Yoray Zack <yor...@mellanox.com>
---
drivers/nvme/host/tcp.c | 188 +++++++++++++++++++++++++++++++++++++++
include/linux/nvme-tcp.h | 2 +
2 files changed, 190 insertions(+)
diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 8f4f29f18b8c..06711ac095f2 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -62,6 +62,7 @@ enum nvme_tcp_queue_flags {
NVME_TCP_Q_ALLOCATED = 0,
NVME_TCP_Q_LIVE = 1,
NVME_TCP_Q_POLLING = 2,
+ NVME_TCP_Q_OFFLOADS = 3,
};
enum nvme_tcp_recv_state {
@@ -110,6 +111,8 @@ struct nvme_tcp_queue {
void (*state_change)(struct sock *);
void (*data_ready)(struct sock *);
void (*write_space)(struct sock *);
+
+ atomic64_t resync_req;
};
struct nvme_tcp_ctrl {
@@ -129,6 +132,8 @@ struct nvme_tcp_ctrl {
struct delayed_work connect_work;
struct nvme_tcp_request async_req;
u32 io_queues[HCTX_MAX_TYPES];
+
+ struct net_device *offloading_netdev;
};
static LIST_HEAD(nvme_tcp_ctrl_list);
@@ -223,6 +228,159 @@ static inline size_t nvme_tcp_pdu_last_send(struct
nvme_tcp_request *req,
return nvme_tcp_pdu_data_left(req) <= len;
}
+#ifdef CONFIG_TCP_DDP
+
+bool nvme_tcp_resync_request(struct sock *sk, u32 seq, u32 flags);
+const struct tcp_ddp_ulp_ops nvme_tcp_ddp_ulp_ops __read_mostly = {
+ .resync_request = nvme_tcp_resync_request,
+};
+
+static
+int nvme_tcp_offload_socket(struct nvme_tcp_queue *queue,
+ struct nvme_tcp_config *config)
+{
+ struct net_device *netdev = get_netdev_for_sock(queue->sock->sk, true);
+ struct tcp_ddp_config *ddp_config = (struct tcp_ddp_config *)config;
+ int ret;
+
+ if (unlikely(!netdev)) {
Let's remove unlikely from non datapath routines, its slightly
confusing.
+ pr_info_ratelimited("%s: netdev not found\n", __func__);
dev_info_ratelimited with queue->ctrl->ctrl.device ?
Also, lets remove __func__. This usually is not very helpful.
+ return -EINVAL;
+ }
+
+ if (!(netdev->features & NETIF_F_HW_TCP_DDP)) {
+ dev_put(netdev);
+ return -EINVAL;
EINVAL or ENODEV?
+ }
+
+ ret = netdev->tcp_ddp_ops->tcp_ddp_sk_add(netdev,
+ queue->sock->sk,
+ ddp_config);
+ if (!ret)
+ inet_csk(queue->sock->sk)->icsk_ulp_ddp_ops =
&nvme_tcp_ddp_ulp_ops;
+ else
+ dev_put(netdev);
+ return ret;
+}
+
+static
+void nvme_tcp_unoffload_socket(struct nvme_tcp_queue *queue)
+{
+ struct net_device *netdev = queue->ctrl->offloading_netdev;
+
+ if (unlikely(!netdev)) {
+ pr_info_ratelimited("%s: netdev not found\n", __func__);
Same here.
+ return;
+ }
+
+ netdev->tcp_ddp_ops->tcp_ddp_sk_del(netdev, queue->sock->sk);
+
+ inet_csk(queue->sock->sk)->icsk_ulp_ddp_ops = NULL;
Just a general question, why is this needed?
+ dev_put(netdev); /* put the queue_init get_netdev_for_sock() */
+}
+
+static
+int nvme_tcp_offload_limits(struct nvme_tcp_queue *queue,
+ struct tcp_ddp_limits *limits)
+{
+ struct net_device *netdev = get_netdev_for_sock(queue->sock->sk, true);
+ int ret = 0;
+
+ if (unlikely(!netdev)) {
+ pr_info_ratelimited("%s: netdev not found\n", __func__);
+ return -EINVAL;
Same here
+ }
+
+ if (netdev->features & NETIF_F_HW_TCP_DDP &&
+ netdev->tcp_ddp_ops &&
+ netdev->tcp_ddp_ops->tcp_ddp_limits)
+ ret = netdev->tcp_ddp_ops->tcp_ddp_limits(netdev,
limits);
+ else
+ ret = -EOPNOTSUPP;
+
+ if (!ret) {
+ queue->ctrl->offloading_netdev = netdev;
+ pr_info("%s netdev %s offload limits: max_ddp_sgl_len %d\n",
+ __func__, netdev->name, limits->max_ddp_sgl_len);
dev_info, and given that it per-queue, please make it dev_dbg.
+ queue->ctrl->ctrl.max_segments = limits->max_ddp_sgl_len;
+ queue->ctrl->ctrl.max_hw_sectors =
+ limits->max_ddp_sgl_len << (ilog2(SZ_4K) - 9);
+ } else {
+ queue->ctrl->offloading_netdev = NULL;
Maybe nullify in the controller setup intead?
+ }
+
+ dev_put(netdev);
+
+ return ret;
+}
+
+static
+void nvme_tcp_resync_response(struct nvme_tcp_queue *queue,
+ unsigned int pdu_seq)
+{
+ struct net_device *netdev = queue->ctrl->offloading_netdev;
+ u64 resync_val;
+ u32 resync_seq;
+
+ if (unlikely(!netdev)) {
+ pr_info_ratelimited("%s: netdev not found\n", __func__);
+ return;
What happens now, fallback to SW? Maybe dev_warn then..
will the SW keep seeing these responses after one failed?
+ }
+
+ resync_val = atomic64_read(&queue->resync_req);
+ if ((resync_val & TCP_DDP_RESYNC_REQ) == 0)
+ return;
+
+ resync_seq = resync_val >> 32;
+ if (before(pdu_seq, resync_seq))
+ return;
I think it will be better to pass the skb to this func and keep the
pdu_seq contained locally.
+
+ if (atomic64_cmpxchg(&queue->resync_req, resync_val, (resync_val - 1)))
+ netdev->tcp_ddp_ops->tcp_ddp_resync(netdev, queue->sock->sk,
pdu_seq);
A small comment on this manipulation may help the reader.
+}
+
+bool nvme_tcp_resync_request(struct sock *sk, u32 seq, u32 flags)
+{
+ struct nvme_tcp_queue *queue = sk->sk_user_data;
+
+ atomic64_set(&queue->resync_req,
+ (((uint64_t)seq << 32) | flags));
+
+ return true;
+}
+
+#else
+
+static
+int nvme_tcp_offload_socket(struct nvme_tcp_queue *queue,
+ struct nvme_tcp_config *config)
+{
+ return -EINVAL;
+}
+
+static
+void nvme_tcp_unoffload_socket(struct nvme_tcp_queue *queue)
+{}
+
+static
+int nvme_tcp_offload_limits(struct nvme_tcp_queue *queue,
+ struct tcp_ddp_limits *limits)
+{
+ return -EINVAL;
+}
+
+static
+void nvme_tcp_resync_response(struct nvme_tcp_queue *queue,
+ unsigned int pdu_seq)
+{}
+
+bool nvme_tcp_resync_request(struct sock *sk, u32 seq, u32 flags)
+{
+ return false;
+}
+
+#endif
+
static void nvme_tcp_init_iter(struct nvme_tcp_request *req,
unsigned int dir)
{
@@ -628,6 +786,11 @@ static int nvme_tcp_recv_pdu(struct nvme_tcp_queue *queue,
struct sk_buff *skb,
size_t rcv_len = min_t(size_t, *len, queue->pdu_remaining);
int ret;
+ u64 pdu_seq = TCP_SKB_CB(skb)->seq + *offset - queue->pdu_offset;
+
+ if (test_bit(NVME_TCP_Q_OFFLOADS, &queue->flags))
+ nvme_tcp_resync_response(queue, pdu_seq);
Here, just pass in (queue, skb)
+
ret = skb_copy_bits(skb, *offset,
&pdu[queue->pdu_offset], rcv_len);
if (unlikely(ret))
@@ -1370,6 +1533,8 @@ static int nvme_tcp_alloc_queue(struct nvme_ctrl *nctrl,
{
struct nvme_tcp_ctrl *ctrl = to_tcp_ctrl(nctrl);
struct nvme_tcp_queue *queue = &ctrl->queues[qid];
+ struct nvme_tcp_config config;
+ struct tcp_ddp_limits limits;
int ret, rcv_pdu_size;
queue->ctrl = ctrl;
@@ -1487,6 +1652,26 @@ static int nvme_tcp_alloc_queue(struct nvme_ctrl *nctrl,
#endif
write_unlock_bh(&queue->sock->sk->sk_callback_lock);
+ if (nvme_tcp_queue_id(queue) != 0) {
if (!nvme_tcp_admin_queue(queue)) {
+ config.cfg.type = TCP_DDP_NVME;
+ config.pfv = NVME_TCP_PFV_1_0;
+ config.cpda = 0;
+ config.dgst = queue->hdr_digest ?
+ NVME_TCP_HDR_DIGEST_ENABLE : 0;
+ config.dgst |= queue->data_digest ?
+ NVME_TCP_DATA_DIGEST_ENABLE : 0;
+ config.queue_size = queue->queue_size;
+ config.queue_id = nvme_tcp_queue_id(queue);
+ config.io_cpu = queue->io_cpu;
Can the config initialization move to nvme_tcp_offload_socket?
+
+ ret = nvme_tcp_offload_socket(queue, &config);
+ if (!ret)
+ set_bit(NVME_TCP_Q_OFFLOADS, &queue->flags);
+ } else {
+ ret = nvme_tcp_offload_limits(queue, &limits);
+ }
I'm thinking that instead of this conditional, we want to place
nvme nvme_tcp_alloc_admin_queue in nvme_tcp_alloc_admin_queue, and
also move nvme_tcp_alloc_admin_queue to __nvme_tcp_alloc_io_queues
loop.
+ /* offload is opportunistic - failure is non-critical */
Than make it void...
+
return 0;
err_init_connect:
@@ -1519,6 +1704,9 @@ static void __nvme_tcp_stop_queue(struct nvme_tcp_queue
*queue)
kernel_sock_shutdown(queue->sock, SHUT_RDWR);
nvme_tcp_restore_sock_calls(queue);
cancel_work_sync(&queue->io_work);
+
+ if (test_bit(NVME_TCP_Q_OFFLOADS, &queue->flags))
+ nvme_tcp_unoffload_socket(queue);
Why not in nvme_tcp_free_queue, symmetric to the alloc?
}
static void nvme_tcp_stop_queue(struct nvme_ctrl *nctrl, int qid)
diff --git a/include/linux/nvme-tcp.h b/include/linux/nvme-tcp.h
index 959e0bd9a913..65df64c34ecd 100644
--- a/include/linux/nvme-tcp.h
+++ b/include/linux/nvme-tcp.h
@@ -8,6 +8,8 @@
#define _LINUX_NVME_TCP_H
#include <linux/nvme.h>
+#include <net/sock.h>
+#include <net/tcp_ddp.h>
Why is this needed? I think we want to place this in tcp.c no?
