Re: [PATCH] tcm_vhost: Multi-queue support

["Nicholas A. Bellinger" <nab@linux-iscsi.org>]

On Wed, 2013-02-06 at 13:20 +0800, Asias He wrote:
> This adds virtio-scsi multi-queue support to tcm_vhost.
> 
> Guest side virtio-scsi multi-queue support can be found here:
> 
>    https://lkml.org/lkml/2012/12/18/166
> 
> Some initial perf numbers:
> 1 queue,  4 targets, 1 lun per target
> 4K request size, 50% randread + 50% randwrite: 127K/127k IOPS
> 
> 4 queues, 4 targets, 1 lun per target
> 4K request size, 50% randread + 50% randwrite: 181K/181k IOPS
> 

Nice single LUN small block random I/O improvement here with 4x vqueues.

Curious to see how virtio-scsi small block performance looks with
SCSI-core to multi-LUN tcm_vhost endpoints as well..  8-)

Btw, this does not apply atop current target-pending.git/for-next with
your other pending vhost patch series, and AFAICT this patch is supposed
to apply on top of your last PATCH-v3, no..?

--nab

> Signed-off-by: Asias He <asias@redhat.com>
> ---
>  drivers/vhost/tcm_vhost.c | 46 +++++++++++++++++++++++++++++-----------------
>  drivers/vhost/tcm_vhost.h |  2 ++
>  2 files changed, 31 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
> index 81ecda5..9951297 100644
> --- a/drivers/vhost/tcm_vhost.c
> +++ b/drivers/vhost/tcm_vhost.c
> @@ -48,6 +48,7 @@
>  #include <linux/virtio_net.h> /* TODO vhost.h currently depends on this */
>  #include <linux/virtio_scsi.h>
>  #include <linux/llist.h>
> +#include <linux/bitmap.h>
>  
>  #include "vhost.c"
>  #include "vhost.h"
> @@ -59,7 +60,8 @@ enum {
>  	VHOST_SCSI_VQ_IO = 2,
>  };
>  
> -#define VHOST_SCSI_MAX_TARGET 256
> +#define VHOST_SCSI_MAX_TARGET	256
> +#define VHOST_SCSI_MAX_VQ	128
>  
>  struct vhost_scsi {
>  	/* Protected by vhost_scsi->dev.mutex */
> @@ -68,7 +70,7 @@ struct vhost_scsi {
>  	bool vs_endpoint;
>  
>  	struct vhost_dev dev;
> -	struct vhost_virtqueue vqs[3];
> +	struct vhost_virtqueue vqs[VHOST_SCSI_MAX_VQ];
>  
>  	struct vhost_work vs_completion_work; /* cmd completion work item */
>  	struct llist_head vs_completion_list; /* cmd completion queue */
> @@ -366,12 +368,14 @@ static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
>  {
>  	struct vhost_scsi *vs = container_of(work, struct vhost_scsi,
>  					vs_completion_work);
> +	DECLARE_BITMAP(signal, VHOST_SCSI_MAX_VQ);
>  	struct virtio_scsi_cmd_resp v_rsp;
>  	struct tcm_vhost_cmd *tv_cmd;
>  	struct llist_node *llnode;
>  	struct se_cmd *se_cmd;
> -	int ret;
> +	int ret, vq;
>  
> +	bitmap_zero(signal, VHOST_SCSI_MAX_VQ);
>  	llnode = llist_del_all(&vs->vs_completion_list);
>  	while (llnode) {
>  		tv_cmd = llist_entry(llnode, struct tcm_vhost_cmd,
> @@ -390,15 +394,20 @@ static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
>  		memcpy(v_rsp.sense, tv_cmd->tvc_sense_buf,
>  		       v_rsp.sense_len);
>  		ret = copy_to_user(tv_cmd->tvc_resp, &v_rsp, sizeof(v_rsp));
> -		if (likely(ret == 0))
> -			vhost_add_used(&vs->vqs[2], tv_cmd->tvc_vq_desc, 0);
> -		else
> +		if (likely(ret == 0)) {
> +			vhost_add_used(tv_cmd->tvc_vq, tv_cmd->tvc_vq_desc, 0);
> +			vq = tv_cmd->tvc_vq - vs->vqs;
> +			__set_bit(vq, signal);
> +		} else
>  			pr_err("Faulted on virtio_scsi_cmd_resp\n");
>  
>  		vhost_scsi_free_cmd(tv_cmd);
>  	}
>  
> -	vhost_signal(&vs->dev, &vs->vqs[2]);
> +	vq = -1;
> +	while ((vq = find_next_bit(signal, VHOST_SCSI_MAX_VQ, vq + 1))
> +		< VHOST_SCSI_MAX_VQ)
> +		vhost_signal(&vs->dev, &vs->vqs[vq]);
>  }
>  
>  static struct tcm_vhost_cmd *vhost_scsi_allocate_cmd(
> @@ -561,9 +570,9 @@ static void tcm_vhost_submission_work(struct work_struct *work)
>  	}
>  }
>  
> -static void vhost_scsi_handle_vq(struct vhost_scsi *vs)
> +static void vhost_scsi_handle_vq(struct vhost_scsi *vs,
> +	struct vhost_virtqueue *vq)
>  {
> -	struct vhost_virtqueue *vq = &vs->vqs[2];
>  	struct virtio_scsi_cmd_req v_req;
>  	struct tcm_vhost_tpg *tv_tpg;
>  	struct tcm_vhost_cmd *tv_cmd;
> @@ -656,7 +665,7 @@ static void vhost_scsi_handle_vq(struct vhost_scsi *vs)
>  			ret = __copy_to_user(resp, &rsp, sizeof(rsp));
>  			if (!ret)
>  				vhost_add_used_and_signal(&vs->dev,
> -						&vs->vqs[2], head, 0);
> +							  vq, head, 0);
>  			else
>  				pr_err("Faulted on virtio_scsi_cmd_resp\n");
>  
> @@ -678,6 +687,7 @@ static void vhost_scsi_handle_vq(struct vhost_scsi *vs)
>  			": %d\n", tv_cmd, exp_data_len, data_direction);
>  
>  		tv_cmd->tvc_vhost = vs;
> +		tv_cmd->tvc_vq = vq;
>  
>  		if (unlikely(vq->iov[out].iov_len !=
>  				sizeof(struct virtio_scsi_cmd_resp))) {
> @@ -758,7 +768,7 @@ static void vhost_scsi_handle_kick(struct vhost_work *work)
>  						poll.work);
>  	struct vhost_scsi *vs = container_of(vq->dev, struct vhost_scsi, dev);
>  
> -	vhost_scsi_handle_vq(vs);
> +	vhost_scsi_handle_vq(vs, vq);
>  }
>  
>  /*
> @@ -879,7 +889,7 @@ err:
>  static int vhost_scsi_open(struct inode *inode, struct file *f)
>  {
>  	struct vhost_scsi *s;
> -	int r;
> +	int r, i;
>  
>  	s = kzalloc(sizeof(*s), GFP_KERNEL);
>  	if (!s)
> @@ -889,8 +899,9 @@ static int vhost_scsi_open(struct inode *inode, struct file *f)
>  
>  	s->vqs[VHOST_SCSI_VQ_CTL].handle_kick = vhost_scsi_ctl_handle_kick;
>  	s->vqs[VHOST_SCSI_VQ_EVT].handle_kick = vhost_scsi_evt_handle_kick;
> -	s->vqs[VHOST_SCSI_VQ_IO].handle_kick = vhost_scsi_handle_kick;
> -	r = vhost_dev_init(&s->dev, s->vqs, 3);
> +	for (i = VHOST_SCSI_VQ_IO; i < VHOST_SCSI_MAX_VQ; i++)
> +		s->vqs[i].handle_kick = vhost_scsi_handle_kick;
> +	r = vhost_dev_init(&s->dev, s->vqs, VHOST_SCSI_MAX_VQ);
>  	if (r < 0) {
>  		kfree(s);
>  		return r;
> @@ -922,9 +933,10 @@ static void vhost_scsi_flush_vq(struct vhost_scsi *vs, int index)
>  
>  static void vhost_scsi_flush(struct vhost_scsi *vs)
>  {
> -	vhost_scsi_flush_vq(vs, VHOST_SCSI_VQ_CTL);
> -	vhost_scsi_flush_vq(vs, VHOST_SCSI_VQ_EVT);
> -	vhost_scsi_flush_vq(vs, VHOST_SCSI_VQ_IO);
> +	int i;
> +
> +	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)
> +		vhost_scsi_flush_vq(vs, i);
>  }
>  
>  static int vhost_scsi_set_features(struct vhost_scsi *vs, u64 features)
> diff --git a/drivers/vhost/tcm_vhost.h b/drivers/vhost/tcm_vhost.h
> index 519a550..1d2ae7a 100644
> --- a/drivers/vhost/tcm_vhost.h
> +++ b/drivers/vhost/tcm_vhost.h
> @@ -23,6 +23,8 @@ struct tcm_vhost_cmd {
>  	struct virtio_scsi_cmd_resp __user *tvc_resp;
>  	/* Pointer to vhost_scsi for our device */
>  	struct vhost_scsi *tvc_vhost;
> +	/* Pointer to vhost_virtqueue for the cmd */
> +	struct vhost_virtqueue *tvc_vq;
>  	/* Pointer to vhost nexus memory */
>  	struct tcm_vhost_nexus *tvc_nexus;
>  	/* The TCM I/O descriptor that is accessed via container_of() */