netdev - Re: Re: Re: Re: limited network bandwidth with 3.2.x kernels

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Message-ID: <6857224.s9gmvGgyqq@localhost.localdomain>
Date:	Wed, 22 Feb 2012 03:26:19 +0200
From:	alekcejk@...glemail.com
To:	Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org
Subject: Re: Re: Re: Re: limited network bandwidth with 3.2.x kernels

В сообщении от Вторник 21 февраля 2012 18:31:24 вы написали:
> > But maximum speed in 3.1.10 kernel (without this sysctl settings) still
> > a bit more than in 3.2.7 - 11 MB/s instead of 10.3 MB/s.
> > 
> > --2012-02-21 18:56:36--  ftp://ftp3.de.freebsd.org/pub/FreeBSD/ISO-IMAGES-i386/8.2/FreeBSD-8.2-RELEASE-i386-dvd1.iso.xz
> > 100%[======================================>] 2 066 424 512 11,0M/s   in 3m 30s
> > 2012-02-21 19:13:55 (9,39 MB/s) - «/dev/null» saved [2066424512]
> 
> Thats one measure, you'll have to make a lot of different measures to
> make this significant, preferably in a lab to rule out different
> external network conditions.

So, I did a couple of download tests from ftp3.de.freebsd.org with kernel 3.1.10.

Here traffic plot for net.ipv4.tcp_rmem="4096 87380 897664":
http://img848.imageshack.us/img848/2425/net897664.png

Here plot for net.ipv4.tcp_rmem="4096 87380 4127616":
http://img14.imageshack.us/img14/311/net4127616.png

And comparison of both plots:
http://img684.imageshack.us/img684/7163/netoh.png

The main notable difference is that with 4127616 there is
never stright line (when wget shows 11 M/s ) as with  897664.
Speed with 4127616 is close to 11 M/s but never constant.
I was able to reproduce this at least 3 times.

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