linux-kernel - Re: [PATCH v2 net-next] net: core: use listified Rx for GRO_NORMAL in napi_gro

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Date:   Mon, 25 Nov 2019 16:39:55 +0300
From:   Alexander Lobakin <alobakin@...nk.ru>
To:     Edward Cree <ecree@...arflare.com>
Cc:     Paolo Abeni <pabeni@...hat.com>,
        Johannes Berg <johannes@...solutions.net>,
        Nicholas Johnson <nicholas.johnson-opensource@...look.com.au>,
        David Miller <davem@...emloft.net>, jiri@...lanox.com,
        edumazet@...gle.com, idosch@...lanox.com, petrm@...lanox.com,
        sd@...asysnail.net, f.fainelli@...il.com,
        jaswinder.singh@...aro.org, ilias.apalodimas@...aro.org,
        linux-kernel@...r.kernel.org, emmanuel.grumbach@...el.com,
        luciano.coelho@...el.com, linuxwifi@...el.com,
        kvalo@...eaurora.org, netdev@...r.kernel.org,
        linux-wireless@...r.kernel.org
Subject: Re: [PATCH v2 net-next] net: core: use listified Rx for GRO_NORMAL in
 napi_gro_receive()

Edward Cree wrote 25.11.2019 16:21:
> On 25/11/2019 12:02, Alexander Lobakin wrote:
>> I'm not very familiar with iwlwifi, but as a work around manual
>> napi_gro_flush() you can also manually flush napi->rx_list to
>> prevent packets from stalling:
>> 
>> diff -Naur a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c 
>> b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
>> --- a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c    2019-11-25 
>> 14:55:03.610355230 +0300
>> +++ b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c    2019-11-25 
>> 14:57:29.399556868 +0300
>> @@ -1526,8 +1526,16 @@
>>      if (unlikely(emergency && count))
>>          iwl_pcie_rxq_alloc_rbs(trans, GFP_ATOMIC, rxq);
>> 
>> -    if (rxq->napi.poll)
>> +    if (rxq->napi.poll) {
>> +        if (rxq->napi.rx_count) {
>> +            netif_receive_skb_list(&rxq->napi.rx_list);
>> +
>> +            INIT_LIST_HEAD(&rxq->napi.rx_list);
>> +            rxq->napi.rx_count = 0;
>> +        }
>> +
>>          napi_gro_flush(&rxq->napi, false);
>> +    }
>> 
>>      iwl_pcie_rxq_restock(trans, rxq);
>>  }
> ... or we could export gro_normal_list(), instead of open-coding it
>  in the driver?

I thought about this too, but don't like it. This patch is proposed as
a *very* temporary solution until iwlwifi will get more straightforward
logic. I wish we could make napi_gro_flush() static in the future and
keep gro_normal_list() private to:

- prevent them from using in any new drivers;
- give more opportunity to CC to optimize the core code.

> 
> -Ed

Regards,
ᚷ ᛖ ᚢ ᚦ ᚠ ᚱ