Messages in this thread | | | Date | Tue, 25 Aug 2009 15:05:22 +0200 | From | Brice Goglin <> | Subject | how to get a DMA channel near a process? |
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Hello,
I am playing with DMA engine on a Nehalem box with two X58 chipsets (Supermicro X8DAH). My understanding is that there are 8 DMA channels on each chipset, so 8 channels near each processor. Unfortunately, my BIOS and 2.6.31-rc still wrongly reports the physical location of my devices (it claims all PCI devices are near the first processor) but I worked around the problem manually.
The offloaded copy performance changes a lot depending on whether the process memory is allocated near the DMA device. So first I would like to know if DMA channels are allocated near the requesting processor/process. Then I guess it's possible to read the cpu mask near a given chan by following chan->dev.device up to the pci device, right? But is there any way to request a DMA channel near a specific socket or NUMA node or cpu mask?
Thanks, Brice
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