On Tue, Feb 07, 2017 at 08:26:23AM -0800, Eric Dumazet wrote: > On Tue, 2017-02-07 at 08:06 -0800, Eric Dumazet wrote: >
Awesome that you've started working on this. I think it's correct approach and mlx5 should be cleaned up in similar way. Long term we should be able to move all page alloc/free out of the drivers completely. > > /* > > * make sure we read the CQE after we read the ownership bit > > */ > > dma_rmb(); > > + prefetch(frags[0].page); > > Note that I would like to instead do a prefetch(frags[1].page) yeah, this two look weird: + prefetch(frags[0].page); + va = page_address(frags[0].page) + frags[0].page_offset; on most archs page_addres() is just math (not a load from memory), but the result != frags[0].page, so I'm missing what are you trying to prefetch? prefetch(frags[1].page) is even more confusing. what will it prefetch? btw we had a patch that was doing prefetch of 'va' of next packet and it was very helpful. Like this: pref_index = (index + 1) & ring->size_mask; pref = ring->rx_info + (pref_index << priv->log_rx_info); prefetch(page_address(pref->page) + pref->page_offset); but since you're redesigning rxing->rx_info... not sure how will it fit. > So I will probably change how ring->rx_info is allocated > > wasting all that space and forcing vmalloc() is silly : > > tmp = size * roundup_pow_of_two(MLX4_EN_MAX_RX_FRAGS * > sizeof(struct mlx4_en_rx_alloc)); I think you'd still need roundup_pow_of_two otherwise priv->log_rx_info optimization won't work.
