Subject: Re: [PATCH v2 net-next 1/4] net: xdp: introduce bulking for xdp tx return path

From: Lorenzo Bianconi <[email-masked]>
Date: Fri, 30 Oct 2020 09:22:47 +0100

> Hi Lorenzo, 
> 
> On Thu, Oct 29, 2020 at 08:28:44PM +0100, Lorenzo Bianconi wrote:
[...]
> > index 54b0bf574c05..43ab8a73900e 100644
> > --- a/drivers/net/ethernet/marvell/mvneta.c
> > +++ b/drivers/net/ethernet/marvell/mvneta.c
> > @@ -1834,8 +1834,10 @@ static void mvneta_txq_bufs_free(struct mvneta_port *pp,
> >  				 struct netdev_queue *nq, bool napi)
> >  {
> >  	unsigned int bytes_compl = 0, pkts_compl = 0;
> > +	struct xdp_frame_bulk bq;
> >  	int i;
> >  
> > +	bq.xa = NULL;
> >  	for (i = 0; i < num; i++) {
> >  		struct mvneta_tx_buf *buf = &txq->buf[txq->txq_get_index];
> >  		struct mvneta_tx_desc *tx_desc = txq->descs +
> > @@ -1857,9 +1859,10 @@ static void mvneta_txq_bufs_free(struct mvneta_port *pp,
> >  			if (napi && buf->type == MVNETA_TYPE_XDP_TX)
> >  				xdp_return_frame_rx_napi(buf->xdpf);
> >  			else
> > -				xdp_return_frame(buf->xdpf);
> > +				xdp_return_frame_bulk(buf->xdpf, &bq);
> >  		}
> >  	}
> > +	xdp_flush_frame_bulk(&bq);
> >  
> >  	netdev_tx_completed_queue(nq, pkts_compl, bytes_compl);
> >  }
> 
> Sorry I completely forgot to mention this on the v1 review.
> I think this belongs to a patch of it's own similar to mellanox and mvpp2 
> drivers

ack, I am fine with it. I will fix it in v3.

Regards,
Lorenzo

> 
> > diff --git a/include/net/xdp.h b/include/net/xdp.h
> > index 3814fb631d52..a1f48a73e6df 100644
> > --- a/include/net/xdp.h
> > +++ b/include/net/xdp.h
> > @@ -104,6 +104,12 @@ struct xdp_frame {
> >  	struct net_device *dev_rx; /* used by cpumap */
> >  };
> >  
> > +#define XDP_BULK_QUEUE_SIZE	16
> > +struct xdp_frame_bulk {
> > +	int count;
> > +	void *xa;
> > +	void *q[XDP_BULK_QUEUE_SIZE];
> > +};
> >  
> >  static inline struct skb_shared_info *
> >  xdp_get_shared_info_from_frame(struct xdp_frame *frame)
> > @@ -194,6 +200,9 @@ struct xdp_frame *xdp_convert_buff_to_frame(struct xdp_buff *xdp)
> >  void xdp_return_frame(struct xdp_frame *xdpf);
> >  void xdp_return_frame_rx_napi(struct xdp_frame *xdpf);
> >  void xdp_return_buff(struct xdp_buff *xdp);
> > +void xdp_flush_frame_bulk(struct xdp_frame_bulk *bq);
> > +void xdp_return_frame_bulk(struct xdp_frame *xdpf,
> > +			   struct xdp_frame_bulk *bq);
> >  
> >  /* When sending xdp_frame into the network stack, then there is no
> >   * return point callback, which is needed to release e.g. DMA-mapping
> > diff --git a/net/core/xdp.c b/net/core/xdp.c
> > index 48aba933a5a8..66ac275a0360 100644
> > --- a/net/core/xdp.c
> > +++ b/net/core/xdp.c
> > @@ -380,6 +380,67 @@ void xdp_return_frame_rx_napi(struct xdp_frame *xdpf)
> >  }
> >  EXPORT_SYMBOL_GPL(xdp_return_frame_rx_napi);
> >  
> > +/* XDP bulk APIs introduce a defer/flush mechanism to return
> > + * pages belonging to the same xdp_mem_allocator object
> > + * (identified via the mem.id field) in bulk to optimize
> > + * I-cache and D-cache.
> > + * The bulk queue size is set to 16 to be aligned to how
> > + * XDP_REDIRECT bulking works. The bulk is flushed when
> > + * it is full or when mem.id changes.
> > + * xdp_frame_bulk is usually stored/allocated on the function
> > + * call-stack to avoid locking penalties.
> > + */
> > +void xdp_flush_frame_bulk(struct xdp_frame_bulk *bq)
> > +{
> > +	struct xdp_mem_allocator *xa = bq->xa;
> > +	int i;
> > +
> > +	if (unlikely(!xa))
> > +		return;
> > +
> > +	for (i = 0; i < bq->count; i++) {
> > +		struct page *page = virt_to_head_page(bq->q[i]);
> > +
> > +		page_pool_put_full_page(xa->page_pool, page, false);
> > +	}
> > +	bq->count = 0;
> > +}
> > +EXPORT_SYMBOL_GPL(xdp_flush_frame_bulk);
> > +
> > +void xdp_return_frame_bulk(struct xdp_frame *xdpf,
> > +			   struct xdp_frame_bulk *bq)
> > +{
> > +	struct xdp_mem_info *mem = &xdpf->mem;
> > +	struct xdp_mem_allocator *xa;
> > +
> > +	if (mem->type != MEM_TYPE_PAGE_POOL) {
> > +		__xdp_return(xdpf->data, &xdpf->mem, false);
> > +		return;
> > +	}
> > +
> > +	rcu_read_lock();
> > +
> > +	xa = bq->xa;
> > +	if (unlikely(!xa)) {
> > +		xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
> > +		bq->count = 0;
> > +		bq->xa = xa;
> > +	}
> > +
> > +	if (bq->count == XDP_BULK_QUEUE_SIZE)
> > +		xdp_flush_frame_bulk(bq);
> > +
> > +	if (mem->id != xa->mem.id) {
> > +		xdp_flush_frame_bulk(bq);
> > +		bq->xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
> > +	}
> > +
> > +	bq->q[bq->count++] = xdpf->data;
> > +
> > +	rcu_read_unlock();
> > +}
> > +EXPORT_SYMBOL_GPL(xdp_return_frame_bulk);
> > +
> >  void xdp_return_buff(struct xdp_buff *xdp)
> >  {
> >  	__xdp_return(xdp->data, &xdp->rxq->mem, true);
> > -- 
> > 2.26.2
> > 
> 
> 
> Cheers
> /Ilias