netdev - Re: [PATCH net-next] tcp/fq: move back to CLOCK

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Message-ID: <418cfd90-1f5c-abb8-6fbb-0d436ed87374@gmail.com>
Date:   Fri, 28 Sep 2018 14:52:17 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Leonard Crestez <leonard.crestez@....com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "eric.dumazet@...il.com" <eric.dumazet@...il.com>
Subject: Re: [PATCH net-next] tcp/fq: move back to CLOCK_MONOTONIC



On 09/28/2018 02:27 PM, Leonard Crestez wrote:
> On Fri, 2018-09-28 at 10:28 -0700, Eric Dumazet wrote:
>> In the recent TCP/EDT patch series, I switched TCP and sch_fq
>> clocks from MONOTONIC to TAI, in order to meet the choice done
>> earlier for sch_etf packet scheduler.
>>
>> But sure enough, this broke some setups were the TAI clock
>> jumps forward (by almost 50 year...), as reported
>> by Leonard Crestez.
>>
>> If we want to converge later, we'll probably need to add
>> an skb field to differentiate the clock bases, or a socket option.
>>
>> In the meantime, an UDP application will need to use CLOCK_MONOTONIC
>> base for its SCM_TXTIME timestamps if using fq packet scheduler.
>>
>> Fixes: 72b0094f9182 ("tcp: switch tcp_clock_ns() to CLOCK_TAI base")
>> Fixes: 142537e41923 ("net_sched: sch_fq: switch to CLOCK_TAI")
>> Fixes: fd2bca2aa789 ("tcp: switch internal pacing timer to CLOCK_TAI")
>> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
>> Reported-by: Leonard Crestez <leonard.crestez@....com>
> 
> Tested-by: Leonard Crestez <leonard.crestez@....com>
> 
> Fixes the problem reported earlier when applied on top of next-20180928
> 

Thanks again ;)