netdev - Re: [PATCH net-next 2/4] net: page_pool: add bulk support for ptr

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Date:   Thu, 29 Oct 2020 11:37:45 +0100
From:   Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
To:     Ilias Apalodimas <ilias.apalodimas@...aro.org>
Cc:     Lorenzo Bianconi <lorenzo@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, davem@...emloft.net, kuba@...nel.org,
        brouer@...hat.com
Subject: Re: [PATCH net-next 2/4] net: page_pool: add bulk support for
 ptr_ring

> On Tue, Oct 27, 2020 at 08:04:08PM +0100, Lorenzo Bianconi wrote:
> > Introduce the capability to batch page_pool ptr_ring refill since it is
> > usually run inside the driver NAPI tx completion loop.
> > 
> > Suggested-by: Jesper Dangaard Brouer <brouer@...hat.com>
> > Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> > ---
> >  include/net/page_pool.h | 26 ++++++++++++++++++++++++++
> >  net/core/page_pool.c    | 33 +++++++++++++++++++++++++++++++++
> >  net/core/xdp.c          |  9 ++-------
> >  3 files changed, 61 insertions(+), 7 deletions(-)
> > 
> > diff --git a/include/net/page_pool.h b/include/net/page_pool.h
> > index 81d7773f96cd..b5b195305346 100644

[...]

> > +void page_pool_put_page_bulk(struct page_pool *pool, void **data,
> > +			     int count)
> > +{
> > +	struct page *page_ring[XDP_BULK_QUEUE_SIZE];
> > +	int i, len = 0;
> > +
> > +	for (i = 0; i < count; i++) {
> > +		struct page *page = virt_to_head_page(data[i]);
> > +
> > +		if (unlikely(page_ref_count(page) != 1 ||
> > +			     !pool_page_reusable(pool, page))) {
> > +			page_pool_release_page(pool, page);
> > +			put_page(page);
> > +			continue;
> > +		}
> > +
> > +		if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
> > +			page_pool_dma_sync_for_device(pool, page, -1);
> > +
> > +		page_ring[len++] = page;
> > +	}
> > +
> > +	page_pool_ring_lock(pool);
> > +	for (i = 0; i < len; i++) {
> > +		if (__ptr_ring_produce(&pool->ring, page_ring[i]))
> > +			page_pool_return_page(pool, page_ring[i]);
> 
> Can we add a comment here on why the explicit spinlock needs to protect 
> page_pool_return_page() as well instead of just using ptr_ring_produce()?

ack, will do in v2.

Regards,
Lorenzo

> 
> > +	}
> > +	page_pool_ring_unlock(pool);
> > +}
> > +EXPORT_SYMBOL(page_pool_put_page_bulk);
> > +
> >  static void page_pool_empty_ring(struct page_pool *pool)
> >  {
> >  	struct page *page;
> > diff --git a/net/core/xdp.c b/net/core/xdp.c
> > index 93eabd789246..9f9a8d14df38 100644
> > --- a/net/core/xdp.c
> > +++ b/net/core/xdp.c
> > @@ -383,16 +383,11 @@ EXPORT_SYMBOL_GPL(xdp_return_frame_rx_napi);
> >  void xdp_flush_frame_bulk(struct xdp_frame_bulk *bq)
> >  {
> >  	struct xdp_mem_allocator *xa = bq->xa;
> > -	int i;
> >  
> > -	if (unlikely(!xa))
> > +	if (unlikely(!xa || !bq->count))
> >  		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);
> > -	}
> > +	page_pool_put_page_bulk(xa->page_pool, bq->q, bq->count);
> >  	bq->count = 0;
> >  }
> >  EXPORT_SYMBOL_GPL(xdp_flush_frame_bulk);
> > -- 
> > 2.26.2
> > 
> 
> Thanks
> /Ilias
> 

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