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From: Eric Dumazet <eric.dumazet@gmail.com>
To: Christoph Paasch <christoph.paasch@gmail.com>,
	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 20:44:30 -0700	[thread overview]
Message-ID: <aa0af451-5e7c-7d83-ef25-095a67cd23a1@gmail.com> (raw)
In-Reply-To: <CALMXkpZ4isoXpFp_5=nVUcWrt5TofYVhpdAjv7LkCH7RFW1tYw@mail.gmail.com>



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.

Really TCP can not work well with tiny sndbuf limits.

There is really no point trying to be nice.

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.

  reply	other threads:[~2019-06-18  3:44 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 [this message]
2019-06-18  3:53           ` Christoph Paasch
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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