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From:   Hayes Wang <hayeswang@realtek.com>
To:     Jakub Kicinski <kuba@kernel.org>
CC:     "davem@davemloft.net" <davem@davemloft.net>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        nic_swsd <nic_swsd@realtek.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>
Subject: RE: [PATCH net v2] r8152: avoid the driver drops a lot of packets
Thread-Topic: [PATCH net v2] r8152: avoid the driver drops a lot of packets
Thread-Index: AQHZ4G/uLCHLeDMawES5jAj/REiJSrAN/YuAgADpM2A=
Date:   Thu, 7 Sep 2023 07:16:50 +0000
Message-ID: <7f8b32a91f5849c99609f78520b23535@realtek.com>
References: <20230906031148.16774-421-nic_swsd@realtek.com>
 <20230906172847.2b3b749a@kernel.org>
In-Reply-To: <20230906172847.2b3b749a@kernel.org>
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Jakub Kicinski <kuba@kernel.org>
> Sent: Thursday, September 7, 2023 8:29 AM
[...]
> Good to see that you can repro the problem.

I don't reproduce the problem. I just find some information about it.

> Before we tweak the heuristics let's make sure rx_bottom() behaves
> correctly. Could you make sure that
>  - we don't perform _any_ rx processing when budget is 0
>    (see the NAPI documentation under Documentation/networking)

The work_done would be 0, and napi_complete_done() wouldn't be called.
However, skb_queue_len(&tp->rx_queue) may be increased. I think it is
not acceptable, right?

>  - finish the current aggregate even if budget run out, return
>    work_done = budget in that case.
>    With this change the rx_queue thing should be gone completely.

Excuse me. I don't understand this part. I know that when the packets are
more than budget, the maximum packets which could be handled is budget.
That is, return work_done = budget. However, the extra packets would be queued
to rx_queue. I don't understand what you mean about " the rx_queue thing
should be gone completely". I think the current driver would return
work_done = budget, and queue the other packets. I don't sure what you
want me to change.

>  - instead of copying the head use napi_get_frags() + napi_gro_frags()
>    it gives you an skb, you just attach the page to it as a frag and
>    hand it back to GRO. This makes sure you never pull data into head
>    rather than just headers.

I would study about them. Thanks.

Should I include above changes for this patch?
I think I have to submit another patches for above.

> Please share the performance results with those changes.

I couldn't reproduce the problem, so I couldn't provide the result
with the differences.


Best Regards,
Hayes