Re: [patch 09/10 v3] raid5: raid5d handle stripe in batch way

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On Mon, 25 Jun 2012 15:24:56 +0800 Shaohua Li <shli@xxxxxxxxxx> wrote:

> Let raid5d handle stripe in batch way to reduce conf->device_lock locking.
> 
> Signed-off-by: Shaohua Li <shli@xxxxxxxxxxxx>
> ---
>  drivers/md/raid5.c |   45 ++++++++++++++++++++++++++++++++-------------
>  1 file changed, 32 insertions(+), 13 deletions(-)
> 
> Index: linux/drivers/md/raid5.c
> ===================================================================
> --- linux.orig/drivers/md/raid5.c	2012-06-25 14:38:37.378835415 +0800
> +++ linux/drivers/md/raid5.c	2012-06-25 14:38:40.150800523 +0800
> @@ -4568,6 +4568,30 @@ static int  retry_aligned_read(struct r5
>  	return handled;
>  }
>  
> +#define MAX_STRIPE_BATCH 8
> +static int handle_active_stripes(struct r5conf *conf)
> +{
> +	struct stripe_head *batch[MAX_STRIPE_BATCH], *sh;
> +	int i, batch_size = 0;
> +
> +	while (batch_size < MAX_STRIPE_BATCH &&
> +			(sh = __get_priority_stripe(conf)) != NULL)
> +		batch[batch_size++] = sh;
> +
> +	if (batch_size == 0)
> +		return batch_size;
> +	spin_unlock_irq(&conf->device_lock);
> +
> +	for (i = 0; i < batch_size; i++)
> +		handle_stripe(batch[i]);
> +
> +	cond_resched();
> +
> +	spin_lock_irq(&conf->device_lock);
> +	for (i = 0; i < batch_size; i++)
> +		__release_stripe(conf, batch[i]);
> +	return batch_size;
> +}
>  
>  /*
>   * This is our raid5 kernel thread.
> @@ -4578,7 +4602,6 @@ static int  retry_aligned_read(struct r5
>   */
>  static void raid5d(struct mddev *mddev)
>  {
> -	struct stripe_head *sh;
>  	struct r5conf *conf = mddev->private;
>  	int handled;
>  	struct blk_plug plug;
> @@ -4592,6 +4615,7 @@ static void raid5d(struct mddev *mddev)
>  	spin_lock_irq(&conf->device_lock);
>  	while (1) {
>  		struct bio *bio;
> +		int batch_size;
>  
>  		if (atomic_read(&mddev->plug_cnt) == 0 &&
>  		    !list_empty(&conf->bitmap_list)) {
> @@ -4616,21 +4640,16 @@ static void raid5d(struct mddev *mddev)
>  			handled++;
>  		}
>  
> -		sh = __get_priority_stripe(conf);
> -
> -		if (!sh)
> +		batch_size = handle_active_stripes(conf);
> +		if (!batch_size)
>  			break;
> -		spin_unlock_irq(&conf->device_lock);
> -		
> -		handled++;
> -		handle_stripe(sh);
> -		release_stripe(sh);
> -		cond_resched();
> +		handled += batch_size;
>  
> -		if (mddev->flags & ~(1<<MD_CHANGE_PENDING))
> +		if (mddev->flags & ~(1<<MD_CHANGE_PENDING)) {
> +			spin_unlock_irq(&conf->device_lock);
>  			md_check_recovery(mddev);
> -
> -		spin_lock_irq(&conf->device_lock);
> +			spin_lock_irq(&conf->device_lock);
> +		}
>  	}
>  	pr_debug("%d stripes handled\n", handled);
>  
> 


I've applied this patch, thanks.

NeilBrown

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