netdev - Re: [PATCH v5 net-next 2/3] net: page_pool: add the possibility to sync DMA memory for device

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Date:   Wed, 20 Nov 2019 20:00:38 +0200
From:   Ilias Apalodimas <ilias.apalodimas@...aro.org>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     Lorenzo Bianconi <lorenzo@...nel.org>, netdev@...r.kernel.org,
        davem@...emloft.net, lorenzo.bianconi@...hat.com,
        mcroce@...hat.com, jonathan.lemon@...il.com
Subject: Re: [PATCH v5 net-next 2/3] net: page_pool: add the possibility to
 sync DMA memory for device

> [...]
> > @@ -281,8 +309,8 @@ static bool __page_pool_recycle_direct(struct page *page,
> >  	return true;
> >  }
> >  
> > -void __page_pool_put_page(struct page_pool *pool,
> > -			  struct page *page, bool allow_direct)
> > +void __page_pool_put_page(struct page_pool *pool, struct page *page,
> > +			  unsigned int dma_sync_size, bool allow_direct)
> >  {
> >  	/* This allocator is optimized for the XDP mode that uses
> >  	 * one-frame-per-page, but have fallbacks that act like the
> > @@ -293,6 +321,10 @@ void __page_pool_put_page(struct page_pool *pool,
> >  	if (likely(page_ref_count(page) == 1)) {
> >  		/* Read barrier done in page_ref_count / READ_ONCE */
> >  
> > +		if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
> > +			page_pool_dma_sync_for_device(pool, page,
> > +						      dma_sync_size);
> > +
> >  		if (allow_direct && in_serving_softirq())
> >  			if (__page_pool_recycle_direct(page, pool))
> >  				return;
> 
> I am slightly concerned this touch the fast-path code. But at-least on
> Intel, I don't think this is measurable.  And for the ARM64 board it
> was a huge win... thus I'll accept this.

Acked-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>