Commit 2324c78a authored by Furong Xu's avatar Furong Xu Committed by Paolo Abeni
Browse files

net: stmmac: Set page_pool_params.max_len to a precise size 



DMA engine will always write no more than dma_buf_sz bytes of a received
frame into a page buffer, the remaining spaces are unused or used by CPU
exclusively.
Setting page_pool_params.max_len to almost the full size of page(s) helps
nothing more, but wastes more CPU cycles on cache maintenance.

For a standard MTU of 1500, then dma_buf_sz is assigned to 1536, and this
patch brings ~16.9% driver performance improvement in a TCP RX
throughput test with iPerf tool on a single isolated Cortex-A65 CPU
core, from 2.43 Gbits/sec increased to 2.84 Gbits/sec.

Signed-off-by: default avatarFurong Xu <0x1207@gmail.com>
Reviewed-by: default avatarAlexander Lobakin <aleksander.lobakin@intel.com>
Reviewed-by: default avatarYanteng Si <si.yanteng@linux.dev>
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent df542f66

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

+1 −1
Original line number Diff line number Diff line
@@ -2059,7 +2059,7 @@ static int __alloc_dma_rx_desc_resources(struct stmmac_priv *priv, 
	pp_params.dev = priv->device;

	pp_params.dma_dir = xdp_prog ? DMA_BIDIRECTIONAL : DMA_FROM_DEVICE;

	pp_params.offset = stmmac_rx_offset(priv);

	pp_params.max_len = STMMAC_MAX_RX_BUF_SIZE(num_pages);

	pp_params.max_len = dma_conf->dma_buf_sz;



	rx_q->page_pool = page_pool_create(&pp_params);

	if (IS_ERR(rx_q->page_pool)) {

drivers/net/ethernet/stmicro/stmmac/stmmac_xdp.h

+0 −1
Original line number Diff line number Diff line
@@ -4,7 +4,6 @@ 
#ifndef _STMMAC_XDP_H_

#define _STMMAC_XDP_H_



#define STMMAC_MAX_RX_BUF_SIZE(num)	(((num) * PAGE_SIZE) - XDP_PACKET_HEADROOM)

#define STMMAC_RX_DMA_ATTR	(DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_WEAK_ORDERING)



int stmmac_xdp_setup_pool(struct stmmac_priv *priv, struct xsk_buff_pool *pool,