netdev - Re: [PATCH net-next v2] octeontx2-pf: Add support for page pool

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Date: Fri, 19 May 2023 09:41:30 +0800
From: Yunsheng Lin <linyunsheng@...wei.com>
To: Ratheesh Kannoth <rkannoth@...vell.com>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
CC: <sgoutham@...vell.com>, <davem@...emloft.net>, <edumazet@...gle.com>,
	<kuba@...nel.org>, <pabeni@...hat.com>, <sbhatta@...vell.com>,
	<gakula@...vell.com>, <schalla@...vell.com>, <hkelam@...vell.com>
Subject: Re: [PATCH net-next v2] octeontx2-pf: Add support for page pool

On 2023/5/18 13:51, Ratheesh Kannoth wrote:
> Page pool for each rx queue enhance rx side performance
> by reclaiming buffers back to each queue specific pool. DMA
> mapping is done only for first allocation of buffers.
> As subsequent buffers allocation avoid DMA mapping,
> it results in performance improvement.
> 
> Image        |  Performance with Linux kernel Packet Generator

Is there any more detailed info for the performance data?
'kernel Packet Generator' means using pktgen module in the
net/core/pktgen.c? it seems pktgen is more for tx, is there
any abvious reason why the page pool optimization for rx have
brought about ten times improvement?

> ------------ | -----------------------------------------------
> Vannila      |   3Mpps
>              |
> with this    |   42Mpps
> change	     |
> -------------------------------------------------------------
> 

...

>  static int __otx2_alloc_rbuf(struct otx2_nic *pfvf, struct otx2_pool *pool,
>  			     dma_addr_t *dma)
>  {
>  	u8 *buf;
>  
> +	if (pool->page_pool)
> +		return otx2_alloc_pool_buf(pfvf, pool, dma);
> +
>  	buf = napi_alloc_frag_align(pool->rbsize, OTX2_ALIGN);
>  	if (unlikely(!buf))
>  		return -ENOMEM;

It seems the above is dead code when using 'select PAGE_POOL', as
PAGE_POOL config is always selected by the driver?

> @@ -1205,10 +1226,28 @@ void otx2_sq_free_sqbs(struct otx2_nic *pfvf)
>  	}
>  }
>  

...

> @@ -1659,7 +1715,6 @@ int otx2_nix_config_bp(struct otx2_nic *pfvf, bool enable)
>  	req->bpid_per_chan = 0;
>  #endif
>  
> -

Nit: unrelated change here.

>  	return otx2_sync_mbox_msg(&pfvf->mbox);
>  }