Bug 691396

Summary:	gigabit eth slow
Product:	[Fedora] Fedora	Reporter:	Arne Woerner <arne_woerner>
Component:	kernel	Assignee:	Kernel Maintainer List <kernel-maint>
Status:	CLOSED NOTABUG	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	medium	Docs Contact:
Priority:	unspecified
Version:	14	CC:	gansalmon, itamar, jonathan, kernel-maint, madhu.chinakonda
Target Milestone:	---
Target Release:	---
Hardware:	x86_64
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2012-01-01 12:44:33 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:

Description Arne Woerner 2011-03-28 12:48:23 UTC

Description of problem:
My gigabit ethernet connection speed is 475Mbits/sec according to iperf (which uses about 85% cpu time on the Atom).
I use a 5m Cat5E cable between
a Realtek 8111DL on a Intel D945GSEJT (Atom N270, i686)
and
a Realtek RTL8111B / RTL8111C on a Asrock ALiveDual-eSATA2 (Athlon64 X2 5000+, x86_64).
ethtool says that there is a full duplex connection.
ifconfig says the MTU is 1500 (different values r worse) and the error rate is 0.
i tried to offload some work to the nic on the Atom board, but the link stopped working or slowed down then...

Version-Release number of selected component (if applicable):
Linux neo.riddick.homeunix.org 2.6.35.11-83.fc14.i686 #1 SMP Mon Feb 7 07:04:18 UTC 2011 i686 i686 i386 GNU/Linux
Linux vaako.riddick.homeunix.org 2.6.35.11-83.fc14.x86_64 #1 SMP Mon Feb 7 07:06:44 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux

How reproducible:
if the link is idle otherwise: always

Steps to Reproduce:
1. connect the cable
2. start iperf
  
Actual results:
475Mbits/sec

Expected results:
800Mbits/sec..900Mbits/sec

Additional info:
1. when i use nc or nfs i get almost the same result (45MB/sec)
2. is the Atom the bottleneck?

Comment 1 Arne Woerner 2012-01-01 12:44:33 UTC

seems like ethernet is more complicated than i thought, so that the Atom cant do more than 475Mbit/sec, although it can read from /dev/zero with 10Gbit/sec... -arne

Comment 2 Arne Woerner 2012-01-24 09:57:45 UTC

addendum:
funnily i get 799Mbit/sec with the same Atom N270 board (fc15) and my new Intel Core i7 (fc16)... :-) *yay*
-arne