Subject: Re: [PATCH net-next v3 2/4] net: stmmac: Set page_pool_params.max_len to a precise size

From: Yanteng Si <[email-masked]>
Date: Wed, 15 Jan 2025 18:07:32 +0800

在 2025/1/15 11:27, Furong Xu 写道:
> 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: Furong Xu <[email-masked]>
> Reviewed-by: Alexander Lobakin <[email-masked]>
Reviewed-by: Yanteng Si <[email-masked]>

Thanks,
Yanteng

> ---
>   drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 2 +-
>   drivers/net/ethernet/stmicro/stmmac/stmmac_xdp.h  | 1 -
>   2 files changed, 1 insertion(+), 2 deletions(-)