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From:   Jonathan Maxwell <jmaxwell37@gmail.com>
Date:   Wed, 11 Jul 2018 10:33:19 +1000
Message-ID: <CAGHK07Aoa81QN+LmVttJQ56Sn+R-KyksYqZxSYL5-5reDRt3WA@mail.gmail.com>
Subject: Re: [net-next,v3] tcp: Improve setsockopt() TCP_USER_TIMEOUT accuracy
To:     Eric Dumazet <eric.dumazet@gmail.com>
Cc:     David Miller <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Neal Cardwell <ncardwell@google.com>,
        David Laight <David.Laight@aculab.com>,
        kuznet <kuznet@ms2.inr.ac.ru>,
        yoshfuji <yoshfuji@linux-ipv6.org>,
        Netdev <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Jon Maxwell <jmaxwell@redhat.com>
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On Tue, Jul 10, 2018 at 10:48 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
>
> On 07/10/2018 05:38 AM, Eric Dumazet wrote:
>
>> Note that if we always do jiffies_to_msecs(icsk->icsk_user_timeout) in TCP,
>> we also could change the convention and store msecs in this field instead of jiffies.
>>
>> That would eliminate the msecs_to_jiffies() and jiffies_to_msecs() dance.
>>
>> (That would be done in a patch of its own, of course)
>
> tcp_keepalive_timer() does use icsk->icsk_user_timeout directly in jiffies unit,
> but considering keeapalive timers are rarely used, this point would have to
> do the msecs_to_jiffies() conversion.

and also if icsk->icsk_user_timeout = 0, then timeout in retransmits_timed_out()
is in jiffies and that would need to addressed.