Messages in this thread | | | From | Alexander Lobakin <> | Subject | Re: [PATCH net-next v2 4/4] net: lan96x: Use page_pool API | Date | Mon, 7 Nov 2022 17:40:55 +0100 |
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From: Horatiu Vultur <horatiu.vultur@microchip.com> Date: Sun, 6 Nov 2022 22:11:54 +0100
> Use the page_pool API for allocation, freeing and DMA handling instead > of dev_alloc_pages, __free_pages and dma_map_page. > > Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com> > --- > .../net/ethernet/microchip/lan966x/Kconfig | 1 + > .../ethernet/microchip/lan966x/lan966x_fdma.c | 72 ++++++++++--------- > .../ethernet/microchip/lan966x/lan966x_main.h | 3 + > 3 files changed, 43 insertions(+), 33 deletions(-)
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> @@ -84,6 +62,27 @@ static void lan966x_fdma_rx_add_dcb(struct lan966x_rx *rx, > rx->last_entry = dcb; > } > > +static int lan966x_fdma_rx_alloc_page_pool(struct lan966x_rx *rx) > +{ > + struct lan966x *lan966x = rx->lan966x; > + struct page_pool_params pp_params = { > + .order = rx->page_order, > + .flags = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV, > + .pool_size = FDMA_DCB_MAX, > + .nid = NUMA_NO_NODE, > + .dev = lan966x->dev, > + .dma_dir = DMA_FROM_DEVICE, > + .offset = 0, > + .max_len = PAGE_SIZE << rx->page_order,
::max_len's primary purpose is to save time on DMA syncs. First of all, you can substract `SKB_DATA_ALIGN(sizeof(struct skb_shared_info))`, your HW never writes to those last couple hundred bytes. But I suggest calculating ::max_len basing on your current MTU value. Let's say you have 16k pages and MTU of 1500, that is a huge difference (except your DMA is always coherent, but I assume that's not the case).
In lan966x_fdma_change_mtu() you do:
max_mtu = lan966x_fdma_get_max_mtu(lan966x); max_mtu += IFH_LEN_BYTES; max_mtu += SKB_DATA_ALIGN(sizeof(struct skb_shared_info)); max_mtu += VLAN_HLEN * 2;
`lan966x_fdma_get_max_mtu(lan966x) + IFH_LEN_BYTES + VLAN_HLEN * 2` (ie 1536 for the MTU of 1500) is your max_len value actually, given that you don't reserve any headroom (which is unfortunate, but I guess you're working on this already, since XDP requires %XDP_PACKET_HEADROOM).
> + }; > + > + rx->page_pool = page_pool_create(&pp_params); > + if (IS_ERR(rx->page_pool)) > + return PTR_ERR(rx->page_pool); > + > + return 0;
return PTR_ERR_OR_ZERO(rx->page_pool);
> +} > + > static int lan966x_fdma_rx_alloc(struct lan966x_rx *rx) > { > struct lan966x *lan966x = rx->lan966x;
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> -- > 2.38.0
Thanks, Olek
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