Re: Perfromance drop on SCSI hard disk
From: Alex,Shi
Date: Thu May 19 2011 - 04:48:53 EST
On Thu, 2011-05-19 at 16:26 +0800, Alex,Shi wrote:
> > I will queue up the combined patch, it looks fine from here as well.
> >
>
> When I have some time to study Jens and shaohua's patch today. I find a
> simpler way to resolved the re-enter issue on starved_list. Following
> Jens' idea, we can just put the starved_list device into kblockd if it
> come from __scsi_queue_insert().
> It can resolve the re-enter issue and recover performance totally, and
> need not a work_struct in every scsi_device. The logic/code also looks a
> bit simpler.
> What's your opinion of this?
BTW, Jens, this patch is against on latest kernel, 2.6.39.
>
>
> Signed-off-by: Alex Shi <alex.shi@xxxxxxxxx>
> ---
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index ec1803a..de7c569 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -74,6 +74,8 @@ struct kmem_cache *scsi_sdb_cache;
> */
> #define SCSI_QUEUE_DELAY 3
>
> +static void scsi_run_queue_async(struct request_queue *q);
> +
> /*
> * Function: scsi_unprep_request()
> *
> @@ -159,7 +161,7 @@ static int __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, int unbusy)
> blk_requeue_request(q, cmd->request);
> spin_unlock_irqrestore(q->queue_lock, flags);
>
> - kblockd_schedule_work(q, &device->requeue_work);
> + scsi_run_queue_async(q);
>
> return 0;
> }
> @@ -395,7 +397,7 @@ static inline int scsi_host_is_busy(struct Scsi_Host *shost)
> * Notes: The previous command was completely finished, start
> * a new one if possible.
> */
> -static void scsi_run_queue(struct request_queue *q)
> +static void __scsi_run_queue(struct request_queue *q, bool async)
> {
> struct scsi_device *sdev = q->queuedata;
> struct Scsi_Host *shost;
> @@ -435,30 +437,35 @@ static void scsi_run_queue(struct request_queue *q)
> &shost->starved_list);
> continue;
> }
> -
> - spin_unlock(shost->host_lock);
> - spin_lock(sdev->request_queue->queue_lock);
> - __blk_run_queue(sdev->request_queue);
> - spin_unlock(sdev->request_queue->queue_lock);
> - spin_lock(shost->host_lock);
> + if (async)
> + blk_run_queue_async(sdev->request_queue);
> + else {
> + spin_unlock(shost->host_lock);
> + spin_lock(sdev->request_queue->queue_lock);
> + __blk_run_queue(sdev->request_queue);
> + spin_unlock(sdev->request_queue->queue_lock);
> + spin_lock(shost->host_lock);
> + }
> }
> /* put any unprocessed entries back */
> list_splice(&starved_list, &shost->starved_list);
> spin_unlock_irqrestore(shost->host_lock, flags);
>
> - blk_run_queue(q);
> + if (async)
> + blk_run_queue_async(q);
> + else
> + blk_run_queue(q);
> }
>
> -void scsi_requeue_run_queue(struct work_struct *work)
> +static void scsi_run_queue(struct request_queue *q)
> {
> - struct scsi_device *sdev;
> - struct request_queue *q;
> -
> - sdev = container_of(work, struct scsi_device, requeue_work);
> - q = sdev->request_queue;
> - scsi_run_queue(q);
> + __scsi_run_queue(q, false);
> }
>
> +static void scsi_run_queue_async(struct request_queue *q)
> +{
> + __scsi_run_queue(q, true);
> +}
> /*
> * Function: scsi_requeue_command()
> *
> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
> index 58584dc..087821f 100644
> --- a/drivers/scsi/scsi_scan.c
> +++ b/drivers/scsi/scsi_scan.c
> @@ -242,7 +242,6 @@ static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,
> int display_failure_msg = 1, ret;
> struct Scsi_Host *shost = dev_to_shost(starget->dev.parent);
> extern void scsi_evt_thread(struct work_struct *work);
> - extern void scsi_requeue_run_queue(struct work_struct *work);
>
> sdev = kzalloc(sizeof(*sdev) + shost->transportt->device_size,
> GFP_ATOMIC);
> @@ -265,7 +264,6 @@ static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,
> INIT_LIST_HEAD(&sdev->event_list);
> spin_lock_init(&sdev->list_lock);
> INIT_WORK(&sdev->event_work, scsi_evt_thread);
> - INIT_WORK(&sdev->requeue_work, scsi_requeue_run_queue);
>
> sdev->sdev_gendev.parent = get_device(&starget->dev);
> sdev->sdev_target = starget;
> diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
> index dd82e02..2d3ec50 100644
> --- a/include/scsi/scsi_device.h
> +++ b/include/scsi/scsi_device.h
> @@ -169,7 +169,6 @@ struct scsi_device {
> sdev_dev;
>
> struct execute_work ew; /* used to get process context on put */
> - struct work_struct requeue_work;
>
> struct scsi_dh_data *scsi_dh_data;
> enum scsi_device_state sdev_state;
>
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