[PATCH v2] nvme-tcp: send quota for nvme_tcp_send_all()

[Hannes Reinecke]

On 10/24/22 17:03, Daniel Wagner wrote:
> Add a send quota in nvme_tcp_send_all() to avoid stalls when sending
> large amounts of requests.
> 
> Cc: Hannes Reinecke <hare at suse.de>
> Signed-off-by: Daniel Wagner <dwagner at suse.de>
> ---
> 
> IMO, this patch might still be a good idea to add. At least in my test
> setup where I only have one ethernet port it makes a big difference
> when accessing the system via ssh. When nvme-tcp is pushing a lot of
> data via the network, the ssh session is completely blocked by the
> storage traffic. With it, the ssh session stays responsive.
> 
> I suspect a proper storage setup would use more than one ethernet
> port.
> 
> Daniel
> 
> v1:
>    https://lore.kernel.org/linux-nvme/20220519062617.39715-4-hare@suse.de/
> 
>   drivers/nvme/host/tcp.c | 17 ++++++++++++++---
>   1 file changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
> index 3e7b29d07c71..84a66ca208c8 100644
> --- a/drivers/nvme/host/tcp.c
> +++ b/drivers/nvme/host/tcp.c
> @@ -308,12 +308,23 @@ static inline void nvme_tcp_advance_req(struct nvme_tcp_request *req,
>   
>   static inline void nvme_tcp_send_all(struct nvme_tcp_queue *queue)
>   {
> -	int ret;
> +	unsigned long deadline = jiffies + msecs_to_jiffies(1);
>   
>   	/* drain the send queue as much as we can... */
>   	do {
> -		ret = nvme_tcp_try_send(queue);
> -	} while (ret > 0);
> +		bool pending = false;
> +		int result;
> +
> +		result = nvme_tcp_try_send(queue);
> +		if (result > 0)
> +			pending = true;
> +		else if (unlikely(result < 0))
> +			return;
> +
> +		if (!pending)
> +			return;
> +
> +	} while (!time_after(jiffies, deadline)); /* quota is exhausted */
>   }
>   
>   static inline bool nvme_tcp_queue_more(struct nvme_tcp_queue *queue)

Looks like a good idea indeed.
One might want to make the deadline configurable, though.
Other than that:

Reviewed-by: Hannes Reinecke <hare at suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare at suse.de                              +49 911 74053 688
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