From: sdrb@onet.eu
To: Neal Cardwell <ncardwell@google.com>
Cc: Netdev <netdev@vger.kernel.org>
Subject: Re: Variable download speed
Date: Wed, 24 Feb 2016 08:48:26 +0100 (CET) [thread overview]
Message-ID: <alpine.LNX.2.20.1602240816180.29937@localhost.localdomain> (raw)
In-Reply-To: <CADVnQy=-oh7Ue=Y0vP4ioGrRs7SeJBNq5bkkDVkpogyLpr+9zA@mail.gmail.com>
On Tue, 23 Feb 2016, Neal Cardwell wrote:
> On Tue, Feb 23, 2016 at 8:57 AM, <sdrb@onet.eu> wrote:
>> I published example pcap file under following link:
>>
>> https://www.dropbox.com/s/v8375ub16seyt1a/test7.pcap?dl=0
>>
>> I hope it is possible to download it without creating dropbox account.
>
> Thanks for the trace. It looks like for the first 0.8 seconds of the
> trace some non-TCP component on the receiving machine (app, CPU, CPU
> power-saving mechanisms, NIC, or NIC driver) is limiting throughput to
> 78Mbit/sec (e.g. the very first window of 10 packets is ACKed at that
> rate). Then the throughput increases to over 200 Mbit/sec. AFAICT it
> doesn't look like the TCP layer is doing anything wrong. I'd look for
> issues with those other components. It might help to report the
> receiver application, receiver CPU type, kernel version, NIC, and NIC
> driver.
Hi,
The receiver application was "wget" using ftp protocol.
Linux kernel is in version 3.4.11-rt19.
Concerning hardware I have not much information about it.
Everything I've got is:
- CPU: ARMv7 Processor rev 1 (v7l)
- NIC: Broadcom PCI: 14e4:aa52
- RAM: 256MB
Unfortunately I've no much info about kernel. Seems like it is some kind
of realtime version. Can this realtime extension cause such effect of
increasing throughput?
I've made a graph with window size and throughput from published
test7.pcap file:
https://www.dropbox.com/s/cwars3oaoax73fh/wget_test_test7pcap_20160224_1.png?dl=0
sdrb
next prev parent reply other threads:[~2016-02-24 7:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-23 11:19 Variable download speed sdrb
2016-02-23 13:28 ` Neal Cardwell
2016-02-23 13:57 ` sdrb
2016-02-23 14:26 ` Neal Cardwell
2016-02-24 7:48 ` sdrb [this message]
2016-02-23 11:24 sdrb
2016-02-23 16:53 ` Rick Jones
2016-02-24 9:59 ` sdrb
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