netdev - Re: [PATCH V3 net-next] TLP: Don't reschedule PTO when there's one outstanding TLP retransmission

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Date:   Mon, 31 Jul 2017 23:04:39 -0400
From:   Neal Cardwell <ncardwell@...gle.com>
To:     maowenan <maowenan@...wei.com>
Cc:     Netdev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Yuchung Cheng <ycheng@...gle.com>,
        Nandita Dukkipati <nanditad@...gle.com>,
        "weiyongjun (A)" <weiyongjun1@...wei.com>,
        Chenweilong <chenweilong@...wei.com>,
        "Wangkefeng (Kevin)" <wangkefeng.wang@...wei.com>
Subject: Re: [PATCH V3 net-next] TLP: Don't reschedule PTO when there's one
 outstanding TLP retransmission

On Mon, Jul 31, 2017 at 11:49 AM, Neal Cardwell <ncardwell@...gle.com> wrote:
> On Sun, Jul 30, 2017 at 11:29 PM, maowenan <maowenan@...wei.com> wrote:
>> [Mao Wenan]please refer to the attachment, test.pkt is packetdrill script.
>> In test.pcap, packet number 17 is the TLP probe, packet number 218 is the
>> retransmission packet because client don't send data packet to server.
>> From the capture time, there are about 6 seconds the retransmission
>> packet can be sent, and this time can be added more as long as client
>> send data packet continually.
>> I have reproduced this issue in Linux 4.13-rc3, 3.10, 4.1. Please check the timing
>> When you use test.pkt to reproduce in your environment.
>
> Thank you for your very nice packetdrill test case illustrating this
> problem! And thanks for verifying that the problem shows up in those
> kernel versions.
>
> We are able to run the script in our environment and both verify that
> the bug is the one we hypothesized, and verify our  proposed patch
> fixes it (the RTO for the TLP happens 221ms after the TLP, instead of
> ~5 secs later). We will send out our proposed patches ASAP.

The timer patches are upstream for review for the "net" branch:

  https://patchwork.ozlabs.org/patch/796057/
  https://patchwork.ozlabs.org/patch/796058/
  https://patchwork.ozlabs.org/patch/796059/

Again, thank you for reporting this and providing a packetdrill script
to reproduce this!

neal