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Eth0 Limitations

 
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Operating Systems Linux Red Hat Eth0 Limitations
# 1  
Old 05-15-2012
Eth0 Limitations

Hi,

I have noticed some performance issues on my RHEL5 server but the memory and CPU utilization on the box is fine.

I have a 1G full duplexed eth0 card and I am suspicious that this may be causing the problem. My eth0 settings are as follows:

Code:
Settings for eth0:
Supported ports: [ TP ]
Supported link modes: 1000baseT/Full 
10000baseT/Full 
Supports auto-negotiation: Yes
Advertised link modes: 1000baseT/Full 
10000baseT/Full 
Advertised auto-negotiation: No
Speed: 1000Mb/s
Duplex: Full
Port: Twisted Pair
PHYAD: 0
Transceiver: internal
Auto-negotiation: on
Supports Wake-on: g
Wake-on: d
Link detected: yes

........and my current Rx & Tx figures are as follows.

Code:
ifconfig eth0
eth0 Link encap:Ethernet HWaddr 9C:8E:99:31:34:A0 
UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1
RX packets:75042475 errors:0 dropped:0 overruns:0 frame:0
TX packets:105451412 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000 
RX bytes:3906089934 (3.6 GiB) TX bytes:269789061 (257.2 MiB)

Can anybody tell me what the limitations of this card is? As a percentage is it currently under stress or is it normal and well within its limitations?

If all looks well I'll examine the app in much more detail but really need to rule this out firstly.

R,
D.
# 2  
Old 05-15-2012
I think you need to post the difference between two samples over a given reasonable period of time.


Depending on what network kit this server is plugged into, auto-negotiation should be avoided. It usually needs turning off on the server and the LAN port. Similarly anywhere where network components are cascaded.
It looks like auto-negotiation is off on your server.

Last edited by methyl; 05-15-2012 at 01:44 PM..
# 3  
Old 05-15-2012
Duffs,

You are confused. One, we'd need to know what card it is and the driver in order to tell you what "limitations" it has.

What are the problems you have had with performance? Do you realize that even a 1Gbit card is really only running around 100 Megabytes per second, assuming your switch can even handle that?


Are you configuring the switch and card as full duplex or as auto detect? Most Gigabit and faster connections recommend auto detection for optimal performance.

Without knowing what your issue is, we cannot help you. Does the app send lots of small packets or fewer large ones? Do you do interrupt coalescence? Are you using Nagle's algorithm?

Have you tuned your kernel parameters?

The metrics you have shown have only told us how many packets have hit the wire, and no time frame, or anything.

Let me ask you. How many gallons should it take for me to get to work by driving?

I have not told you how far it is, how fast I drive, what car it is, how well tuned it is, etc, or the inflation of my tires.

---------- Post updated at 03:22 PM ---------- Previous update was at 11:37 AM ----------

Quote:
Originally Posted by methyl
I think you need to post the difference between two samples over a given reasonable period of time.


Depending on what network kit this server is plugged into, auto-negotiation should be avoided. It usually needs turning off on the server and the LAN port. Similarly anywhere where network components are cascaded.
It looks like auto-negotiation is off on your server.
For gigabit, auto-neg is almost always recommended. Performance deteriorates when they try to force.
# 4  
Old 05-16-2012
Mark,

Ok, it uses the following card and driver:

Code:
# lspci | grep -i eth
0c:04.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5715S Gigabit Ethernet (rev a3)
 
# ethtool -i eth0
driver: be2net

Packet information - Output of sar -n DEV:
Code:
AM IFACE rxpck/s txpck/s rxbyt/s txbyt/s rxcmp/s txcmp/s rxmcst/s
10:00:01 AM eth0 273.90 389.90 96997.29 82105.24 0.00 0.00 0.00

The switch has auto-negotiation enabled.

Nangle's algorithm - now you're taking me back to my college days. And how exactly do you apply/configure Nangle's algorithm in redhat? - I'm curious now.

R,
D.
# 5  
Old 05-16-2012
Nagles (not Nangles) is the TCP_NODELAY option.

However, simply showing how many packets have come and gone shows NOTHING about the performance.

Have you tried using a tool to actually gauge performance and throughput?

Also, how come you are not using the bnx2 driver?
# 6  
Old 05-16-2012
It actually uses the following card:

Emulex Corporation OneConnect 10Gb NIC (be3)

...hence the be2net driver.

Yes have used relic but as mentioned CPU and memory are fine.

Ok I think its time to get down to the nitty gritty of JBOSS application tuning and performance - thanks for your help.

R,
D.
# 7  
Old 05-16-2012
0c:04.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5715S Gigabit Ethernet (rev a3) Shows that it is a Broadcom.

Here's the issue.

STOP. You are going about this in a totally chicken minus head scenario.

You are ignoring the advice given to you. I'm going to do this exactly one last time before I let you float in the water you keep rising around yourself.

What tools have you used, if any, to test the NETWORK, not the memory, not the CPU, etc.

Your first post mentions 1000Mb/s connection. Is your switch 10Gbe? Your MTU size of 1500 will hold you back, and your txqueuelen will also.

You are looking everywhere but where you've been directed.

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