On 01/18/2013 04:35 AM, Nicholas A. Bellinger wrote:
> 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.
No problem.
>
> 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.
Okay.
> 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 {
>
>
--
Asias
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