netdev - Re: [PATCH v4 net-next 3/3] net: mvneta: get rid of huge dma sync in mvneta_rx

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Message-ID: <20191119155143.0683f754@carbon>
Date:   Tue, 19 Nov 2019 15:51:43 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
Cc:     Lorenzo Bianconi <lorenzo@...nel.org>, netdev@...r.kernel.org,
        davem@...emloft.net, ilias.apalodimas@...aro.org,
        mcroce@...hat.com, jonathan.lemon@...il.com, brouer@...hat.com
Subject: Re: [PATCH v4 net-next 3/3] net: mvneta: get rid of huge dma sync
 in mvneta_rx_refill

On Tue, 19 Nov 2019 14:19:11 +0200
Lorenzo Bianconi <lorenzo.bianconi@...hat.com> wrote:

> > On Mon, 18 Nov 2019 15:33:46 +0200
> > Lorenzo Bianconi <lorenzo@...nel.org> wrote:
> >   
> > > diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> > > index f7713c2c68e1..a06d109c9e80 100644
> > > --- a/drivers/net/ethernet/marvell/mvneta.c
> > > +++ b/drivers/net/ethernet/marvell/mvneta.c  
> > [...]  
> > > @@ -2097,8 +2093,10 @@ mvneta_run_xdp(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
> > >  		err = xdp_do_redirect(pp->dev, xdp, prog);
> > >  		if (err) {
> > >  			ret = MVNETA_XDP_DROPPED;
> > > -			page_pool_recycle_direct(rxq->page_pool,
> > > -						 virt_to_head_page(xdp->data));
> > > +			__page_pool_put_page(rxq->page_pool,
> > > +					virt_to_head_page(xdp->data),
> > > +					xdp->data_end - xdp->data_hard_start,
> > > +					true);
> > >  		} else {
> > >  			ret = MVNETA_XDP_REDIR;
> > >  		}
> > > @@ -2107,8 +2105,10 @@ mvneta_run_xdp(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
> > >  	case XDP_TX:
> > >  		ret = mvneta_xdp_xmit_back(pp, xdp);
> > >  		if (ret != MVNETA_XDP_TX)
> > > -			page_pool_recycle_direct(rxq->page_pool,
> > > -						 virt_to_head_page(xdp->data));
> > > +			__page_pool_put_page(rxq->page_pool,
> > > +					virt_to_head_page(xdp->data),
> > > +					xdp->data_end - xdp->data_hard_start,
> > > +					true);
> > >  		break;
> > >  	default:
> > >  		bpf_warn_invalid_xdp_action(act);
> > > @@ -2117,8 +2117,10 @@ mvneta_run_xdp(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
> > >  		trace_xdp_exception(pp->dev, prog, act);
> > >  		/* fall through */
> > >  	case XDP_DROP:
> > > -		page_pool_recycle_direct(rxq->page_pool,
> > > -					 virt_to_head_page(xdp->data));
> > > +		__page_pool_put_page(rxq->page_pool,
> > > +				     virt_to_head_page(xdp->data),
> > > +				     xdp->data_end - xdp->data_hard_start,
> > > +				     true);  
> > 
> > This does beg for the question: Should we create an API wrapper for
> > this in the header file?
> > 
> > But what to name it?
> > 
> > I know Jonathan doesn't like the "direct" part of the  previous function
> > name page_pool_recycle_direct.  (I do considered calling this 'napi'
> > instead, as it would be inline with networking use-cases, but it seemed
> > limited if other subsystem end-up using this).
> > 
> > Does is 'page_pool_put_page_len' sound better?
> > 
> > But I want also want hide the bool 'allow_direct' in the API name.
> > (As it makes it easier to identify users that uses this from softirq)
> > 
> > Going for 'page_pool_put_page_len_napi' starts to be come rather long.  
> 
> What about removing the second 'page'? Something like:
> - page_pool_put_len_napi()

Well, we (unfortunately) already have page_pool_put(), which is used
for refcnt on the page_pool object itself.

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer