From: Eric Dumazet <eric.dumazet@gmail.com>
To: David Miller <davem@davemloft.net>, eric.dumazet@gmail.com
Cc: soheil.kdev@gmail.com, netdev@vger.kernel.org, ycheng@google.com,
ncardwell@google.com, edumazet@google.com, willemb@google.com,
soheil@google.com
Subject: Re: [PATCH V2 net-next 1/2] tcp: send in-queue bytes in cmsg upon read
Date: Mon, 30 Apr 2018 09:01:47 -0700 [thread overview]
Message-ID: <c95883da-51ab-47aa-7ad1-a5bb85935e6b@gmail.com> (raw)
In-Reply-To: <20180430.115605.1094351453502803017.davem@davemloft.net>
On 04/30/2018 08:56 AM, David Miller wrote:
> From: Eric Dumazet <eric.dumazet@gmail.com>
> Date: Mon, 30 Apr 2018 08:43:50 -0700
>
>> I say sort of, because by the time we have any number, TCP might
>> have received more packets anyway.
>
> That's fine.
>
> However, the number reported should have been true at least at some
> finite point in time.
>
> If you allow overlapping changes to either of the two variables during
> the sampling, then you are reporting a number which was never true at
> any point in time.
>
> It is essentially garbage.
Correct.
TCP sockets are read by a single thread really (or synchronized threads),
or garbage is ensured, regardless of how the kernel ensures locking while reporting "queue length"
next prev parent reply other threads:[~2018-04-30 16:01 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-27 18:57 [PATCH V2 net-next 1/2] tcp: send in-queue bytes in cmsg upon read Soheil Hassas Yeganeh
2018-04-27 18:57 ` [PATCH V2 net-next 2/2] selftest: add test for TCP_INQ Soheil Hassas Yeganeh
2018-04-30 15:38 ` [PATCH V2 net-next 1/2] tcp: send in-queue bytes in cmsg upon read David Miller
2018-04-30 15:43 ` Eric Dumazet
2018-04-30 15:56 ` David Miller
2018-04-30 16:01 ` Eric Dumazet [this message]
2018-04-30 16:10 ` David Miller
2018-04-30 16:59 ` Soheil Hassas Yeganeh
2018-04-30 15:59 ` Soheil Hassas Yeganeh
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