> -----Original Message-----
> From: Jakub Kicinski <kuba@xxxxxxxxxx>
> Sent: Thursday, July 20, 2023 12:30 AM
> To: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> Cc: linux-hyperv@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; Dexuan Cui
> <decui@xxxxxxxxxxxxx>; KY Srinivasan <kys@xxxxxxxxxxxxx>; Paul Rosswurm
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> Subject: Re: [PATCH V2,net-next] net: mana: Add page pool for RX buffers
>
> On Tue, 18 Jul 2023 21:48:01 +0000 Haiyang Zhang wrote:
> > Add page pool for RX buffers for faster buffer cycle and reduce CPU
> > usage.
> >
> > The standard page pool API is used.
>
> > @@ -1437,8 +1437,12 @@ static void mana_rx_skb(void *buf_va, struct
> mana_rxcomp_oob *cqe,
> >
> > act = mana_run_xdp(ndev, rxq, &xdp, buf_va, pkt_len);
> >
> > - if (act == XDP_REDIRECT && !rxq->xdp_rc)
> > + if (act == XDP_REDIRECT && !rxq->xdp_rc) {
> > + if (from_pool)
> > + page_pool_release_page(rxq->page_pool,
> > + virt_to_head_page(buf_va));
>
>
> IIUC you should pass the page_pool as the last argument to
> xdp_rxq_info_reg_mem_model() and then the page will be recycled
> by the core, you shouldn't release it.
>
> Not to mention the potential race in releasing the page _after_
> giving its ownership to someone else.
>
> > - page = dev_alloc_page();
> > + if (is_napi) {
> > + page = page_pool_dev_alloc_pages(rxq->page_pool);
> > + *from_pool = true;
> > + } else {
> > + page = dev_alloc_page();
>
> FWIW if you're only calling this outside NAPI during init, when NAPI
> can't yet run, I _think_ it's okay to use page_pool_dev_alloc..
>
> > + pprm.pool_size = RX_BUFFERS_PER_QUEUE;
> > + pprm.napi = &cq->napi;
> > + pprm.dev = gc->dev;
> > + pprm.dma_dir = DMA_FROM_DEVICE;
>
> If you're not setting PP_FLAG_DMA_MAP you don't have to fill in .dev
> and .dma_dir
Thank you for the comments.
I will update the patch.
- Haiyang
