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nvmet-tcp: set MSG_MORE only if we actually have more to send

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When we send PDU data, we want to optimize the tcp stack
operation if we have more data to send. So when we set MSG_MORE
when:
- We have more fragments coming in the batch, or
- We have a more data to send in this PDU
- We don't have a data digest trailer
- We optimize with the SUCCESS flag and omit the NVMe completion
  (used if sq_head pointer update is disabled)

This addresses a regression in QD=1 with SUCCESS flag optimization
as we unconditionally set MSG_MORE when we didn't actually have
more data to send.

Fixes: 7058329538 ("nvmet-tcp: implement C2HData SUCCESS optimization")
Reported-by: Mark Wunderlich <mark.wunderlich@intel.com>
Tested-by: Mark Wunderlich <mark.wunderlich@intel.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Keith Busch <kbusch@kernel.org>
This commit is contained in:
Sagi Grimberg 2020-03-12 16:06:38 -07:00 committed by Keith Busch
parent 9134ae2a25
commit 98fd5c7237
1 changed files with 9 additions and 3 deletions
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12
drivers/nvme/target/tcp.c
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@ -515,7 +515,7 @@ static int nvmet_try_send_data_pdu(struct nvmet_tcp_cmd *cmd)
return 1;
}
static int nvmet_try_send_data(struct nvmet_tcp_cmd *cmd)
static int nvmet_try_send_data(struct nvmet_tcp_cmd *cmd, bool last_in_batch)
{
struct nvmet_tcp_queue *queue = cmd->queue;
int ret;
@ -523,9 +523,15 @@ static int nvmet_try_send_data(struct nvmet_tcp_cmd *cmd)
while (cmd->cur_sg) {
struct page *page = sg_page(cmd->cur_sg);
u32 left = cmd->cur_sg->length - cmd->offset;
int flags = MSG_DONTWAIT;
if ((!last_in_batch && cmd->queue->send_list_len) ||
cmd->wbytes_done + left < cmd->req.transfer_len ||
queue->data_digest || !queue->nvme_sq.sqhd_disabled)
flags |= MSG_MORE;
ret = kernel_sendpage(cmd->queue->sock, page, cmd->offset,
left, MSG_DONTWAIT | MSG_MORE);
left, flags);
if (ret <= 0)
return ret;
@ -660,7 +666,7 @@ static int nvmet_tcp_try_send_one(struct nvmet_tcp_queue *queue,
}
if (cmd->state == NVMET_TCP_SEND_DATA) {
ret = nvmet_try_send_data(cmd);
ret = nvmet_try_send_data(cmd, last_in_batch);
if (ret <= 0)
goto done_send;
}