Re: [PATCH 2/2] ioatdma: add DMA_PRIVATE capabilities flag

[Dan Williams]

On 6/26/13 4:55 PM, "Jon Mason" <jon.mason@xxxxxxxxx> wrote:
>Unfortunately, the dma_find_channel model does not led itself to
>optimal usage of the available channels, as it seems to give out the
>same channel.  Adding some randomizer (or other way to spread the
>channel selection over multiple channels) would be greatly
>beneficial.

Right now the allocation scheme is per-cpu.  If you have multiple
submission contexts on different cpus it should use all available channels.

>Alternatively, adding an async_memcpy_mmio function (and perhaps some
>minimal size to use the DMA engine) would provide a solution that
>would work.

It¹s hard.  The size is arch and use specific so it may be best to leave
it up to the client.

>However, dma_find_channel should be sufficient to get NTB use of DMA
>engines out for review.  I'll clean it up and send it out shortly.
>Thanks for the insight.

Cool, I¹ll take a look.


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