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Re: [PATCH net-next 1/8] ptr_ring: introduce batch dequeuing

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On Tue, Mar 21, 2017 at 12:04:40PM +0800, Jason Wang wrote:
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
>  include/linux/ptr_ring.h | 65 ++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 65 insertions(+)
> 
> diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
> index 6c70444..4771ded 100644
> --- a/include/linux/ptr_ring.h
> +++ b/include/linux/ptr_ring.h
> @@ -247,6 +247,22 @@ static inline void *__ptr_ring_consume(struct ptr_ring *r)
>  	return ptr;
>  }
>  
> +static inline int __ptr_ring_consume_batched(struct ptr_ring *r,
> +					     void **array, int n)
> +{
> +	void *ptr;
> +	int i = 0;
> +
> +	while (i < n) {
> +		ptr = __ptr_ring_consume(r);
> +		if (!ptr)
> +			break;
> +		array[i++] = ptr;
> +	}
> +
> +	return i;
> +}
> +
>  /*
>   * Note: resize (below) nests producer lock within consumer lock, so if you
>   * call this in interrupt or BH context, you must disable interrupts/BH when


This ignores the comment above that function:

/* Note: callers invoking this in a loop must use a compiler barrier,
 * for example cpu_relax().
 */

Also - it looks like it shouldn't matter if reads are reordered but I wonder.
Thoughts? Including some reasoning about it in commit log would be nice.

> @@ -297,6 +313,55 @@ static inline void *ptr_ring_consume_bh(struct ptr_ring *r)
>  	return ptr;
>  }
>  
> +static inline int ptr_ring_consume_batched(struct ptr_ring *r,
> +					   void **array, int n)
> +{
> +	int ret;
> +
> +	spin_lock(&r->consumer_lock);
> +	ret = __ptr_ring_consume_batched(r, array, n);
> +	spin_unlock(&r->consumer_lock);
> +
> +	return ret;
> +}
> +
> +static inline int ptr_ring_consume_batched_irq(struct ptr_ring *r,
> +					       void **array, int n)
> +{
> +	int ret;
> +
> +	spin_lock_irq(&r->consumer_lock);
> +	ret = __ptr_ring_consume_batched(r, array, n);
> +	spin_unlock_irq(&r->consumer_lock);
> +
> +	return ret;
> +}
> +
> +static inline int ptr_ring_consume_batched_any(struct ptr_ring *r,
> +					       void **array, int n)
> +{
> +	unsigned long flags;
> +	int ret;
> +
> +	spin_lock_irqsave(&r->consumer_lock, flags);
> +	ret = __ptr_ring_consume_batched(r, array, n);
> +	spin_unlock_irqrestore(&r->consumer_lock, flags);
> +
> +	return ret;
> +}
> +
> +static inline int ptr_ring_consume_batched_bh(struct ptr_ring *r,
> +					      void **array, int n)
> +{
> +	int ret;
> +
> +	spin_lock_bh(&r->consumer_lock);
> +	ret = __ptr_ring_consume_batched(r, array, n);
> +	spin_unlock_bh(&r->consumer_lock);
> +
> +	return ret;
> +}
> +
>  /* Cast to structure type and call a function without discarding from FIFO.
>   * Function must return a value.
>   * Callers must take consumer_lock.
> -- 
> 2.7.4

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[PATCH net-next 0/8] vhost-net rx batching Jason Wang <jasowang@redhat.com> - 2017-03-21 05:20 +0100
  [PATCH net-next 3/8] tun: export skb_array Jason Wang <jasowang@redhat.com> - 2017-03-21 05:20 +0100
  [PATCH net-next 1/8] ptr_ring: introduce batch dequeuing Jason Wang <jasowang@redhat.com> - 2017-03-21 05:20 +0100
    Re: [PATCH net-next 1/8] ptr_ring: introduce batch dequeuing Sergei Shtylyov <sergei.shtylyov@cogentembedded.com> - 2017-03-21 11:30 +0100
      Re: [PATCH net-next 1/8] ptr_ring: introduce batch dequeuing Jason Wang <jasowang@redhat.com> - 2017-03-22 04:20 +0100
    Re: [PATCH net-next 1/8] ptr_ring: introduce batch dequeuing "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-22 14:50 +0100
      Re: [PATCH net-next 1/8] ptr_ring: introduce batch dequeuing Jason Wang <jasowang@redhat.com> - 2017-03-23 09:10 +0100
  [PATCH net-next 5/8] tun: support receiving skb through msg_control Jason Wang <jasowang@redhat.com> - 2017-03-21 05:20 +0100
  [PATCH net-next 7/8] vhost_net: try batch dequing from skb array Jason Wang <jasowang@redhat.com> - 2017-03-21 05:20 +0100
    Re: [PATCH net-next 7/8] vhost_net: try batch dequing from skb array "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-22 15:20 +0100
      Re: [PATCH net-next 7/8] vhost_net: try batch dequing from skb array Jason Wang <jasowang@redhat.com> - 2017-03-23 10:20 +0100
  [PATCH net-next 4/8] tap: export skb_array Jason Wang <jasowang@redhat.com> - 2017-03-21 05:20 +0100
  [PATCH net-next 6/8] tap: support receiving skb from msg_control Jason Wang <jasowang@redhat.com> - 2017-03-21 05:20 +0100

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