linux-kernel - Re: [PATCH] nvme/tcp: Add wq_unbound modparam for nvme_tcp

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Message-ID: <fc352d23-06e0-4f24-b220-fb87a229eec7@grimberg.me>
Date: Wed, 13 Mar 2024 11:47:16 +0200
From: Sagi Grimberg <sagi@...mberg.me>
To: Li Feng <fengli@...rtx.com>, Keith Busch <kbusch@...nel.org>,
 Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@....de>,
 "open list:NVM EXPRESS DRIVER" <linux-nvme@...ts.infradead.org>,
 open list <linux-kernel@...r.kernel.org>
Cc: Anton.Gavriliuk@....ua
Subject: Re: [PATCH] nvme/tcp: Add wq_unbound modparam for nvme_tcp_wq



On 13/03/2024 10:55, Li Feng wrote:
> The default nvme_tcp_wq will use all CPUs to process tasks. Sometimes it is
> necessary to set CPU affinity to improve performance.
>
> A new module parameter wq_unbound is added here. If set to true, users can
> configure cpu affinity through
> /sys/devices/virtual/workqueue/nvme_tcp_wq/cpumask.
>
> Signed-off-by: Li Feng <fengli@...rtx.com>
> ---
>   drivers/nvme/host/tcp.c | 21 ++++++++++++++++++---
>   1 file changed, 18 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
> index a6d596e05602..5eaa275f436f 100644
> --- a/drivers/nvme/host/tcp.c
> +++ b/drivers/nvme/host/tcp.c
> @@ -36,6 +36,14 @@ static int so_priority;
>   module_param(so_priority, int, 0644);
>   MODULE_PARM_DESC(so_priority, "nvme tcp socket optimize priority");
>   
> +/*
> + * Use the unbound workqueue for nvme_tcp_wq, then we can set the cpu affinity
> + * from sysfs.
> + */
> +static bool wq_unbound;
> +module_param(wq_unbound, bool, 0644);
> +MODULE_PARM_DESC(wq_unbound, "set unbound flag for nvme tcp work queue");

"Use unbound workqueue for nvme-tcp IO context (default false)"

> +
>   /*
>    * TLS handshake timeout
>    */
> @@ -1551,7 +1559,10 @@ static void nvme_tcp_set_queue_io_cpu(struct nvme_tcp_queue *queue)
>   	else if (nvme_tcp_poll_queue(queue))
>   		n = qid - ctrl->io_queues[HCTX_TYPE_DEFAULT] -
>   				ctrl->io_queues[HCTX_TYPE_READ] - 1;
> -	queue->io_cpu = cpumask_next_wrap(n - 1, cpu_online_mask, -1, false);
> +	if (wq_unbound)
> +		queue->io_cpu = WORK_CPU_UNBOUND;
> +	else
> +		queue->io_cpu = cpumask_next_wrap(n - 1, cpu_online_mask, -1, false);
>   }
>   
>   static void nvme_tcp_tls_done(void *data, int status, key_serial_t pskid)
> @@ -2790,6 +2801,8 @@ static struct nvmf_transport_ops nvme_tcp_transport = {
>   
>   static int __init nvme_tcp_init_module(void)
>   {
> +	unsigned int wq_flags = WQ_MEM_RECLAIM | WQ_HIGHPRI;
> +
>   	BUILD_BUG_ON(sizeof(struct nvme_tcp_hdr) != 8);
>   	BUILD_BUG_ON(sizeof(struct nvme_tcp_cmd_pdu) != 72);
>   	BUILD_BUG_ON(sizeof(struct nvme_tcp_data_pdu) != 24);
> @@ -2799,8 +2812,10 @@ static int __init nvme_tcp_init_module(void)
>   	BUILD_BUG_ON(sizeof(struct nvme_tcp_icresp_pdu) != 128);
>   	BUILD_BUG_ON(sizeof(struct nvme_tcp_term_pdu) != 24);
>   
> -	nvme_tcp_wq = alloc_workqueue("nvme_tcp_wq",
> -			WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
> +	if (wq_unbound)
> +		wq_flags |= WQ_UNBOUND | WQ_SYSFS;

I think we should have WQ_SYSFS exposed always. Add it in a seperate patch
that comes before this.

> +
> +	nvme_tcp_wq = alloc_workqueue("nvme_tcp_wq", wq_flags, 0);
>   	if (!nvme_tcp_wq)
>   		return -ENOMEM;
>