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I enabled IOAT but it seems that no data is transferred using DMA for network:

I enabled IOAT in bios. CPU is Intel(R) Xeon(R) CPU E5-2650 v2 @ 2.60GHz. I loaded the module in ubuntu 14.04 (3.11.0-26-generic). This is the relevant message in dmesg:

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

I could not find any option related to DCA in bios but this is the dmesg| grep dca output:

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

I send many large UDP packets 

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

but /sys/class/dma/ shows no bytes is transferred using dma

/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
Masood_mj
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    Did you "To set TCP stack as Intel I/OAT DMA client, TCP receive copy offload should be enabled in kernel configuration."? Ref: [Intel® QuickData Technology Software Guide for Linux](http://www.intel.com/content/dam/doc/white-paper/quickdata-technology-software-guide-for-linux-paper.pdf) – Brian Oct 18 '14 at 19:16
  • But how to enable that? Does that mean I should set CONFIG_NET_DMA=y as a parameter in GRUB_CMDLINE_LINUX_DEFAULT of grub config? Also I don't see that in cat /boot/config-3.11.0-26-generic – Masood_mj Oct 18 '14 at 20:35
  • what does `grep '' /sys/class/dma/dma*/in_use` say ? – Matija Nalis Oct 26 '14 at 23:19
  • /sys/class/dma/dma0chan0/in_use:0 /sys/class/dma/dma10chan0/in_use:0 and all others are also zero. – Masood_mj Oct 27 '14 at 04:51

0 Answers0