linux-kernel - Re: [PATCH net-next v4 4/5] page_pool: remove PP_FLAG_PAGE

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Date:   Wed, 14 Jun 2023 10:19:54 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Yunsheng Lin <linyunsheng@...wei.com>
Cc:     <davem@...emloft.net>, <pabeni@...hat.com>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Yisen Zhuang <yisen.zhuang@...wei.com>,
        Salil Mehta <salil.mehta@...wei.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Sunil Goutham <sgoutham@...vell.com>,
        Geetha sowjanya <gakula@...vell.com>,
        Subbaraya Sundeep <sbhatta@...vell.com>,
        hariprasad <hkelam@...vell.com>,
        Saeed Mahameed <saeedm@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        Felix Fietkau <nbd@....name>,
        Ryder Lee <ryder.lee@...iatek.com>,
        Shayne Chen <shayne.chen@...iatek.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Kalle Valo <kvalo@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        <linux-rdma@...r.kernel.org>, <linux-wireless@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH net-next v4 4/5] page_pool: remove PP_FLAG_PAGE_FRAG
 flag

On Mon, 12 Jun 2023 21:02:55 +0800 Yunsheng Lin wrote:
>  	struct page_pool_params pp_params = {
> -		.flags = PP_FLAG_DMA_MAP | PP_FLAG_PAGE_FRAG |
> -				PP_FLAG_DMA_SYNC_DEV,
> +		.flags = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV,
>  		.order = hns3_page_order(ring),

Does hns3_page_order() set a good example for the users?

static inline unsigned int hns3_page_order(struct hns3_enet_ring *ring)
{
#if (PAGE_SIZE < 8192)
	if (ring->buf_size > (PAGE_SIZE / 2))
		return 1;
#endif
	return 0;
}

Why allocate order 1 pages for buffers which would fit in a single page?
I feel like this soft of heuristic should be built into the API itself.