netdev - Re: [PATCH v3] tcp: fix tp->undo_retrans accounting in tcp_sacktag

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Date:   Tue, 14 Sep 2021 08:17:49 +0800
From:   zhenggy <zhenggy@...natelecom.cn>
To:     Neal Cardwell <ncardwell@...gle.com>,
        Yuchung Cheng <ycheng@...gle.com>, edumazet@...gle.com,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>, qitiepeng@...natelecom.cn,
        wujianguo@...natelecom.cn, liyonglong@...natelecom.cn
Subject: Re: [PATCH v3] tcp: fix tp->undo_retrans accounting in
 tcp_sacktag_one()

Thanks very much for all your comments, i will repost a v4 patch later.

在 2021/9/14 0:27, Neal Cardwell 写道:
> On Mon, Sep 13, 2021 at 12:11 PM Yuchung Cheng <ycheng@...gle.com> wrote:
>>
>> On Mon, Sep 13, 2021 at 8:49 AM Eric Dumazet <edumazet@...gle.com> wrote:
>>>
>>> On Mon, Sep 13, 2021 at 3:51 AM zhenggy <zhenggy@...natelecom.cn> wrote:
>>>>
>>>> Commit 10d3be569243 ("tcp-tso: do not split TSO packets at retransmit
>>>> time") may directly retrans a multiple segments TSO/GSO packet without
>>>> split, Since this commit, we can no longer assume that a retransmitted
>>>> packet is a single segment.
>>>>
>>>> This patch fixes the tp->undo_retrans accounting in tcp_sacktag_one()
>>>> that use the actual segments(pcount) of the retransmitted packet.
>>>>
>>>> Before that commit (10d3be569243), the assumption underlying the
>>>> tp->undo_retrans-- seems correct.
>>>>
>>>> Fixes: 10d3be569243 ("tcp-tso: do not split TSO packets at retransmit time")
>>>>
>>>
>>> nit: We normally do not add an empty line between Fixes: tag and others.
>>>
>>> Reviewed-by: Eric Dumazet <edumazet@...gle.com>
>> Acked-by: Yuchung Cheng <ycheng@...gle.com>
>>
>> This is a nice fix that would increase the effectiveness of TCP undo
>> in high-speed networks.
> 
> Yes, thanks for the fix!
> 
> Acked-by: Neal Cardwell <ncardwell@...gle.com>
> 
> neal
>