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ctinnist
Asked: 2009-06-19 02:56:39 +0800 CST

The same driver for multiple network cards -- performance bottleneck?

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I'm using driver e1000e for multiple Intel network cards (Intel EXPI9402PT, based on 82571EB chip). The problem is that when I'm trying to utilize maximum speed (1GB) on more than one interface, speed on each interface starts to drop down.

For one interface I get: 120435948 bytes/sec.

For two interfaces I get: 61080233 bytes/sec and 60515294 bytes/sec.

For three interfaces I get: 28564020 bytes/sec, 27111184 bytes/sec, 27118907 bytes/sec.

What can be the cause?

EDIT: /proc/interrupts content:

           CPU0       CPU1       CPU2       CPU3       CPU4       CPU5       CPU6       CPU7
106:      17138          0          0          0          0          0          0          0         PCI-MSI  eth0
114:         51          0          0          0     102193          0         20   23745467         PCI-MSI  eth2
122:         51        290         15        271          0       9253        100          0         PCI-MSI  eth3
130:         43        367          0        290        105         39         15          0         PCI-MSI  eth4
138:         43        361        105        210          0        140          0          0         PCI-MSI  eth5
146:         56      67625        100          0          0   17855245          0          0         PCI-MSI  eth6
linux networking drivers ethernet intel

4 Answers

  1. It won't be the driver.

    It's most likely to be a physically shared component, such as interrupts or the PCI bus.

    • 6

  2. Are they sharing the same interrupt (IRQ)? This is probably your bottleneck.

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  3. What is the endpoint of your iperf test? If you are routing through network hardware or combining all output to a single GBe NIC on another machine your bottleneck may be remote.

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  4. I've posted some sysctl magic here. You can try it, see if it helps

    PS. How you benchmarking speed?

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