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From: Eric Dumazet <edumazet@google.com>
To: "Mohamed Abuelfotoh, Hazem" <abuehaze@amazon.com>
Cc: "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>,
	"ycheng@google.com" <ycheng@google.com>,
	"ncardwell@google.com" <ncardwell@google.com>,
	"weiwan@google.com" <weiwan@google.com>,
	"Strohman, Andy" <astroh@amazon.com>,
	"Herrenschmidt, Benjamin" <benh@amazon.com>
Subject: Re: [PATCH net-next] tcp: optimise receiver buffer autotuning initialisation for high latency connections
Date: Mon, 7 Dec 2020 16:25:17 +0100	[thread overview]
Message-ID: <CANn89iL_5QFGQLzxxLyqfNMGiV2wF4CbkY==x5Sh5vqKOTgFtw@mail.gmail.com> (raw)
In-Reply-To: <3F02FF08-EDA6-4DFD-8D93-479A5B05E25A@amazon.com>

On Sat, Dec 5, 2020 at 1:03 PM Mohamed Abuelfotoh, Hazem
<abuehaze@amazon.com> wrote:
>
> Unfortunately few things are missing in this report.
>
>     What is the RTT between hosts in your test ?
>      >>>>>RTT in my test is 162 msec, but I am able to reproduce it with lower RTTs for example I could see the issue downloading from google   endpoint with RTT of 16.7 msec, as mentioned in my previous e-mail the issue is reproducible whenever RTT exceeded 12msec given that    the sender is using bbr.
>
>         RTT between hosts where I run the iperf test.
>         # ping 54.199.163.187
>         PING 54.199.163.187 (54.199.163.187) 56(84) bytes of data.
>         64 bytes from 54.199.163.187: icmp_seq=1 ttl=33 time=162 ms
>         64 bytes from 54.199.163.187: icmp_seq=2 ttl=33 time=162 ms
>         64 bytes from 54.199.163.187: icmp_seq=3 ttl=33 time=162 ms
>         64 bytes from 54.199.163.187: icmp_seq=4 ttl=33 time=162 ms
>
>         RTT between my EC2 instances and google endpoint.
>         # ping 172.217.4.240
>         PING 172.217.4.240 (172.217.4.240) 56(84) bytes of data.
>         64 bytes from 172.217.4.240: icmp_seq=1 ttl=101 time=16.7 ms
>         64 bytes from 172.217.4.240: icmp_seq=2 ttl=101 time=16.7 ms
>         64 bytes from 172.217.4.240: icmp_seq=3 ttl=101 time=16.7 ms
>         64 bytes from 172.217.4.240: icmp_seq=4 ttl=101 time=16.7 ms
>
>     What driver is used at the receiving side ?
>       >>>>>>I am using ENA driver version version: 2.2.10g on the receiver with scatter gathering enabled.
>
>         # ethtool -k eth0 | grep scatter-gather
>         scatter-gather: on
>                 tx-scatter-gather: on
>                 tx-scatter-gather-fraglist: off [fixed]

This ethtool output refers to TX scatter gather, which is not relevant
for this bug.

I see ENA driver might use 16 KB per incoming packet (if ENA_PAGE_SIZE is 16 KB)

Since I can not reproduce this problem with another NIC on x86, I
really wonder if this is not an issue with ENA driver on PowerPC
perhaps ?

  parent reply	other threads:[~2020-12-07 15:26 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-04 18:06 [PATCH net-next] tcp: optimise receiver buffer autotuning initialisation for high latency connections Hazem Mohamed Abuelfotoh
2020-12-04 18:19 ` Mohamed Abuelfotoh, Hazem
2020-12-04 18:41   ` Eric Dumazet
     [not found]     ` <3F02FF08-EDA6-4DFD-8D93-479A5B05E25A@amazon.com>
2020-12-07 15:25       ` Eric Dumazet [this message]
2020-12-07 16:09         ` Mohamed Abuelfotoh, Hazem
2020-12-07 16:22           ` Eric Dumazet
2020-12-07 16:33             ` Neal Cardwell
2020-12-07 17:08               ` Eric Dumazet
2020-12-07 20:09                 ` Mohamed Abuelfotoh, Hazem
2020-12-07 23:22                   ` Eric Dumazet
2020-12-07 17:16               ` Mohamed Abuelfotoh, Hazem
2020-12-07 17:27                 ` Eric Dumazet
2020-12-08 16:28                   ` Mohamed Abuelfotoh, Hazem
2020-12-08 16:30                     ` Mohamed Abuelfotoh, Hazem
2020-12-08 16:46                     ` Eric Dumazet
2020-12-07 16:34             ` Mohamed Abuelfotoh, Hazem
2020-12-07 17:46               ` Greg KH
2020-12-07 17:54                 ` Mohamed Abuelfotoh, Hazem
2020-12-04 19:10 ` Eric Dumazet
2020-12-04 21:28 ` Neal Cardwell
2020-12-07 11:46   ` [PATCH net] tcp: fix receive buffer autotuning to trigger for any valid advertised MSS Hazem Mohamed Abuelfotoh
2020-12-07 18:53     ` Jakub Kicinski

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