已启用 Intel® I/O 加速，但未传输任何字节

Question

我启用了 IOAT，但似乎没有使用网络 DMA 传输数据：

我在 bios 中启用了 IOAT。CPU 是 Intel(R) Xeon(R) CPU E5-2650 v2 @ 2.60GHz。我在 ubuntu 14.04 (3.11.0-26-generic) 中加载了该模块。这是 dmesg 中的相关信息：

dmesg | grep ioat
[    7.314760] ioatdma: Intel(R) QuickData Technology Driver 4.00
[    7.315893] ioatdma 0000:00:04.0: irq 186 for MSI/MSI-X
[    7.317850] ioatdma 0000:00:04.1: irq 187 for MSI/MSI-X
[    7.318319] ioatdma 0000:00:04.2: irq 188 for MSI/MSI-X
[    7.323282] ioatdma 0000:00:04.3: irq 189 for MSI/MSI-X
[    7.323567] ioatdma 0000:00:04.4: irq 190 for MSI/MSI-X
[    7.323855] ioatdma 0000:00:04.5: irq 191 for MSI/MSI-X
[    7.324134] ioatdma 0000:00:04.6: irq 192 for MSI/MSI-X
[    7.324400] ioatdma 0000:00:04.7: irq 193 for MSI/MSI-X
[    7.324759] ioatdma 0000:40:04.0: irq 194 for MSI/MSI-X
[    7.325197] ioatdma 0000:40:04.1: irq 195 for MSI/MSI-X
[    7.325559] ioatdma 0000:40:04.2: irq 196 for MSI/MSI-X
[    7.325828] ioatdma 0000:40:04.3: irq 197 for MSI/MSI-X
[    7.326091] ioatdma 0000:40:04.4: irq 198 for MSI/MSI-X
[    7.326361] ioatdma 0000:40:04.5: irq 199 for MSI/MSI-X
[    7.326620] ioatdma 0000:40:04.6: irq 200 for MSI/MSI-X
[    7.326886] ioatdma 0000:40:04.7: irq 201 for MSI/MSI-X

我在 bios 中找不到任何与 DCA 相关的选项，但这是 dmesg| grep dca 输出：

dmesg | grep dca
[    2.216975] dca service started, version 1.12.1

我发送了很多大的 UDP 数据包

for i in seq 4; do netperf -H 192.168.56.2 -p 12865 -t UDP_STREAM -l 20 -C -c -- -m 65000 -s 16M -S 16M -R 1 &  done

但 /sys/class/dma/ 显示没有使用 dma 传输字节

/sys/class/dma# for i in `seq 0 16`; do cat dma${i}chan0/bytes_transferred; done
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0