Re: [PATCH 0/9] IB: Optimize DMA mapping

[santosh.shilimkar@xxxxxxxxxx]

On 1/10/17 4:56 PM, Bart Van Assche wrote:
> Hello Doug,
>
> As you know there are two sets of DMA mapping operations in the Linux
> kernel:
> - One set of DMA mapping operations that is used by most drivers.
> - Another set of DMA mapping operations that is only used by the RDMA
>   drivers.
> Having two sets of DMA mapping operations is not only a source of
> confusion but also a source of unnecessary overhead. The DMA mapping
> operations are in the hot path so it is important that the overhead
> of these operations is as low as possible. Hence this patch series
> that converts the RDMA code to the standard DMA mapping API and
> thereby eliminates the if (dev->dma_ops) test from the hot path. An
> additional benefit is that the size of HW and SW drivers that do not
> use DMA is reduced by switching to dma_virt_ops.
This is really good series. I was always wondering why the extra
indirection was added first place on streaming APIs.

Regards,
Santosh