I'm running a Zotac NM-10-B-E (equipped with a D510 ATOM cpu and 4GB of RAM) under Ubuntu 10.10 x64. The system is connected to a suitable GbE switch from Linksys. Because the ATOM machine is currently only a testbed the operating system is installed on a SDHC via USB. The workmate on the LAN is a powerfull six core machine, running Win7 x64.
The connection tests are performed with the current versions of iperf
. The problem - I can't exeed ~0.5Gbit
throughput. File transfer tests from and to a local ramdisk on the linux system confirm the result from iperf. All tests were performed trough a direct connection as well.
The cpu workload moves arround 70% while the NIC is transfering/receiving data. The settings on the linux systems for tcp autotuning seem to be sensible. Enough buffer space as well as all advanced setings like selective ACKs, window scaling and so on are active.
In my eyes the linux system, more precise the ATOM, should be capable to handle nearly full speed GbE throughput - at last in synthetic benchmarks like iperf. Could it be a problem of the driver implementation for the NIC?
03:0b.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL-8110SC/8169SC Gigabit Ethernet (rev 10)
Subsystem: ZOTAC International (MCO) Ltd. Device 8167
Flags: bus master, 66MHz, medium devsel, latency 64, IRQ 16
I/O ports at e800 [size=256]
Memory at febdfc00 (32-bit, non-prefetchable) [size=256]
Expansion ROM at febe0000 [disabled] [size=128K]
Capabilities: <access denied>
Kernel driver in use: r8169
Kernel modules: r8169
Any suggestions are welcome!