Hi Asias!
On Sun, 2013-01-06 at 14:36 +0800, Asias He wrote:
> This drops the cmd completion list spin lock and makes the cmd
> completion queue lock-less.
>
> Signed-off-by: Asias He <asias@xxxxxxxxxx>
> ---
Apologies for the long delay to get back to this patch.
After some initial testing, I'm seeing about about a ~5K IOPs
performance increase to single RAMDISK_MCP (~110K to ~115K) on the heavy
mixed 75/25 4k randrw fio workload.
That said, I think it's fine to as a for-3.9 item.
Acked-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
MST, do you want to take this via your vhost tree, or shall I merge via
target-pending/for-next..?
Thanks,
--nab
> drivers/vhost/tcm_vhost.c | 46 +++++++++++++---------------------------------
> drivers/vhost/tcm_vhost.h | 2 +-
> 2 files changed, 14 insertions(+), 34 deletions(-)
>
> diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
> index b20df5c..3720604 100644
> --- a/drivers/vhost/tcm_vhost.c
> +++ b/drivers/vhost/tcm_vhost.c
> @@ -47,6 +47,7 @@
> #include <linux/vhost.h>
> #include <linux/virtio_net.h> /* TODO vhost.h currently depends on this */
> #include <linux/virtio_scsi.h>
> +#include <linux/llist.h>
>
> #include "vhost.c"
> #include "vhost.h"
> @@ -64,8 +65,7 @@ struct vhost_scsi {
> struct vhost_virtqueue vqs[3];
>
> struct vhost_work vs_completion_work; /* cmd completion work item */
> - struct list_head vs_completion_list; /* cmd completion queue */
> - spinlock_t vs_completion_lock; /* protects s_completion_list */
> + struct llist_head vs_completion_list; /* cmd completion queue */
> };
>
> /* Local pointer to allocated TCM configfs fabric module */
> @@ -301,9 +301,7 @@ static void vhost_scsi_complete_cmd(struct tcm_vhost_cmd *tv_cmd)
> {
> struct vhost_scsi *vs = tv_cmd->tvc_vhost;
>
> - spin_lock_bh(&vs->vs_completion_lock);
> - list_add_tail(&tv_cmd->tvc_completion_list, &vs->vs_completion_list);
> - spin_unlock_bh(&vs->vs_completion_lock);
> + llist_add(&tv_cmd->tvc_completion_list, &vs->vs_completion_list);
>
> vhost_work_queue(&vs->dev, &vs->vs_completion_work);
> }
> @@ -347,27 +345,6 @@ static void vhost_scsi_free_cmd(struct tcm_vhost_cmd *tv_cmd)
> kfree(tv_cmd);
> }
>
> -/* Dequeue a command from the completion list */
> -static struct tcm_vhost_cmd *vhost_scsi_get_cmd_from_completion(
> - struct vhost_scsi *vs)
> -{
> - struct tcm_vhost_cmd *tv_cmd = NULL;
> -
> - spin_lock_bh(&vs->vs_completion_lock);
> - if (list_empty(&vs->vs_completion_list)) {
> - spin_unlock_bh(&vs->vs_completion_lock);
> - return NULL;
> - }
> -
> - list_for_each_entry(tv_cmd, &vs->vs_completion_list,
> - tvc_completion_list) {
> - list_del(&tv_cmd->tvc_completion_list);
> - break;
> - }
> - spin_unlock_bh(&vs->vs_completion_lock);
> - return tv_cmd;
> -}
> -
> /* Fill in status and signal that we are done processing this command
> *
> * This is scheduled in the vhost work queue so we are called with the owner
> @@ -377,12 +354,18 @@ static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
> {
> struct vhost_scsi *vs = container_of(work, struct vhost_scsi,
> vs_completion_work);
> + struct virtio_scsi_cmd_resp v_rsp;
> struct tcm_vhost_cmd *tv_cmd;
> + struct llist_node *llnode;
> + struct se_cmd *se_cmd;
> + int ret;
>
> - while ((tv_cmd = vhost_scsi_get_cmd_from_completion(vs))) {
> - struct virtio_scsi_cmd_resp v_rsp;
> - struct se_cmd *se_cmd = &tv_cmd->tvc_se_cmd;
> - int ret;
> + llnode = llist_del_all(&vs->vs_completion_list);
> + while (llnode) {
> + tv_cmd = llist_entry(llnode, struct tcm_vhost_cmd,
> + tvc_completion_list);
> + llnode = llist_next(llnode);
> + se_cmd = &tv_cmd->tvc_se_cmd;
>
> pr_debug("%s tv_cmd %p resid %u status %#02x\n", __func__,
> tv_cmd, se_cmd->residual_count, se_cmd->scsi_status);
> @@ -426,7 +409,6 @@ static struct tcm_vhost_cmd *vhost_scsi_allocate_cmd(
> pr_err("Unable to allocate struct tcm_vhost_cmd\n");
> return ERR_PTR(-ENOMEM);
> }
> - INIT_LIST_HEAD(&tv_cmd->tvc_completion_list);
> tv_cmd->tvc_tag = v_req->tag;
> tv_cmd->tvc_task_attr = v_req->task_attr;
> tv_cmd->tvc_exp_data_len = exp_data_len;
> @@ -859,8 +841,6 @@ static int vhost_scsi_open(struct inode *inode, struct file *f)
> return -ENOMEM;
>
> vhost_work_init(&s->vs_completion_work, vhost_scsi_complete_cmd_work);
> - INIT_LIST_HEAD(&s->vs_completion_list);
> - spin_lock_init(&s->vs_completion_lock);
>
> 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;
> diff --git a/drivers/vhost/tcm_vhost.h b/drivers/vhost/tcm_vhost.h
> index 7e87c63..47ee80b 100644
> --- a/drivers/vhost/tcm_vhost.h
> +++ b/drivers/vhost/tcm_vhost.h
> @@ -34,7 +34,7 @@ struct tcm_vhost_cmd {
> /* Sense buffer that will be mapped into outgoing status */
> unsigned char tvc_sense_buf[TRANSPORT_SENSE_BUFFER];
> /* Completed commands list, serviced from vhost worker thread */
> - struct list_head tvc_completion_list;
> + struct llist_node tvc_completion_list;
> };
>
> struct tcm_vhost_nexus {
--
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