From: Christoph Paasch <christoph.paasch@gmail.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>,
"David S . Miller" <davem@davemloft.net>,
netdev <netdev@vger.kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jonathan Looney <jtl@netflix.com>,
Neal Cardwell <ncardwell@google.com>,
Tyler Hicks <tyhicks@canonical.com>,
Yuchung Cheng <ycheng@google.com>,
Bruce Curtis <brucec@netflix.com>,
Jonathan Lemon <jonathan.lemon@gmail.com>,
Dustin Marquess <dmarquess@apple.com>
Subject: Re: [PATCH net 2/4] tcp: tcp_fragment() should apply sane memory limits
Date: Mon, 17 Jun 2019 20:53:58 -0700 [thread overview]
Message-ID: <CALMXkpYs8KN0DmXV+37grbS0Y4Q-DAM-_GVZy+qWi2dtV+cDPA@mail.gmail.com> (raw)
In-Reply-To: <aa0af451-5e7c-7d83-ef25-095a67cd23a1@gmail.com>
On Mon, Jun 17, 2019 at 8:44 PM Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
>
>
> On 6/17/19 8:19 PM, Christoph Paasch wrote:
> >
> > Yes, this does the trick for my packetdrill-test.
> >
> > I wonder, is there a way we could end up in a situation where we can't
> > retransmit anymore?
> > For example, sk_wmem_queued has grown so much that the new test fails.
> > Then, if we legitimately need to fragment in __tcp_retransmit_skb() we
> > won't be able to do so. So we will never retransmit. And if no ACK
> > comes back in to make some room we are stuck, no?
>
> Well, RTO will eventually fire.
But even the RTO would have to go through __tcp_retransmit_skb(), and
let's say the MTU of the interface changed and thus we need to
fragment. tcp_fragment() would keep on failing then, no? Sure,
eventually we will ETIMEOUT but that's a long way to go.
> Really TCP can not work well with tiny sndbuf limits.
>
> There is really no point trying to be nice.
Sure, fair enough :-)
Christoph
>
> There is precedent in TCP stack where we always allow one packet in RX or TX queue
> even with tiny rcv/sndbuf limits (or global memory pressure)
>
> We only need to make sure to allow having at least one packet in rtx queue as well.
next prev parent reply other threads:[~2019-06-18 3:54 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-17 17:03 [PATCH net 0/4] tcp: make sack processing more robust Eric Dumazet
2019-06-17 17:03 ` [PATCH net 1/4] tcp: limit payload size of sacked skbs Eric Dumazet
2019-06-17 17:14 ` Jonathan Lemon
2019-06-17 17:03 ` [PATCH net 2/4] tcp: tcp_fragment() should apply sane memory limits Eric Dumazet
2019-06-17 17:14 ` Jonathan Lemon
2019-06-18 0:18 ` Christoph Paasch
2019-06-18 2:28 ` Eric Dumazet
2019-06-18 3:19 ` Christoph Paasch
2019-06-18 3:44 ` Eric Dumazet
2019-06-18 3:53 ` Christoph Paasch [this message]
2019-06-18 4:08 ` Eric Dumazet
2019-07-10 18:23 ` Prout, Andrew - LLSC - MITLL
2019-07-10 18:28 ` Eric Dumazet
2019-07-10 18:53 ` Prout, Andrew - LLSC - MITLL
2019-07-10 19:26 ` Eric Dumazet
2019-07-11 7:28 ` Christoph Paasch
2019-07-11 9:19 ` Eric Dumazet
2019-07-11 18:26 ` Michal Kubecek
2019-07-11 18:50 ` Eric Dumazet
2019-07-11 10:18 ` Eric Dumazet
2019-07-11 17:14 ` Prout, Andrew - LLSC - MITLL
2019-07-11 18:28 ` Eric Dumazet
2019-07-11 19:04 ` Jonathan Lemon
2019-07-12 7:05 ` Eric Dumazet
2019-07-16 15:13 ` Prout, Andrew - LLSC - MITLL
2019-06-17 17:03 ` [PATCH net 3/4] tcp: add tcp_min_snd_mss sysctl Eric Dumazet
2019-06-17 17:15 ` Jonathan Lemon
2019-06-17 17:18 ` Tyler Hicks
2019-06-17 17:03 ` [PATCH net 4/4] tcp: enforce tcp_min_snd_mss in tcp_mtu_probing() Eric Dumazet
2019-06-17 17:16 ` Jonathan Lemon
2019-06-17 17:18 ` Tyler Hicks
2019-06-17 17:41 ` [PATCH net 0/4] tcp: make sack processing more robust David Miller
2019-08-02 19:02 [PATCH net 2/4] tcp: tcp_fragment() should apply sane memory limits Bernd
2019-08-02 19:14 ` Neal Cardwell
2019-08-02 19:58 ` Bernd
2019-08-14 14:41 ` Marcelo Ricardo Leitner
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