Olivier Langlois's blog

BOOKS i'm reading

Napoleon Hill Keys to Success: The 17 Principles of Personal Achievement, Napoleon Hill, ISBN: 978-0452272811

The 4-Hour Workweek: Escape 9-5, Live Anywhere, and Join the New Rich (Expanded and Updated), Timothy Ferriss, ISBN: 978-0307465351

The Fountainhead, Ayn Rand, ISBN: 0452273331

01/03/16

11:11:03 pm, by lano1106, 107 words, 6734 views

Categories: C++, C++, C++

C++ in the city in 2016 (0x07E0)

This is an editorial that I sent out to my LinkedIn C++ group members:
https://www.linkedin.com/groups/2035024/2035024-6089655206256144384

I'm discussing the retirement of of one of my favorite C++ books author: Scott Meyers
I am remembering the context when Scott Meyers books were hot and just out of the printers in the 90s. What other books of the same era that did pass as well the test of time.

I'm telling what he was meaning for me as a C++ developer and I am inviting people to discuss the impact and the causes of Mr. Meyers retirement.

Go read about it. It is very good!

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09/17/15

11:33:38 pm, by lano1106, 224 words, 3251 views

Categories: TCP/IP

Problem reach maximum transfer speed with 10Gbits Ethernet

I saw a very entertaining youtube video where the host has tested 10 Gbits Ethernet cards on a LAN to perform file transfers. He somehow could not reach the maximum theoritical transfer speed. Here is my explanation why and it is probably that simple:

I do not know what was the protocol underneath for the transfer but if it is TCP, there is something called the bandwidth-delay product that says that in order to keep the network pipe full, you need sufficient TCP send and receive buffers.

Let me show you how to compute that. RTT is basically given by ping. Lets assume worse case scenario with a RTT of 0.2 mSec. 10Gbit/sec is 1250MB/sec or 1,250,000,000 B/sec.

1,250,000,000 B/sec * 0.0002 sec = 250,000B or 250KB. Last time I have checked (I'm a Linux guy) default Windows TCP buffers size were something around 16KB or perhaps 64KB. These are the parameters that you would need to play with to get close to the 10GB/sec rates.

You can change the default value through the registry or on a per connection basis with the socket API.

If we take your maximum transfer rate in your video which was roughly about 360MB/sec and plug it in the bandwidth delay product formula, I get 72KB which is very close to 64KB. Pretty sure that this is your problem!

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