On Mon, Feb 24, 2014 at 01:03:32PM -0600, Joel Fernandes wrote: > Hi folks, > > Just wanted your thoughts/suggestions on how we can avoid overhead in the EDMA > dmaengine driver. I am seeing a lots of performance drop specially for small > transfers with EDMA versus before raw EDMA was moved to DMAEngine framework > (atleast 25%). I've seen roughly the same drop in my testing. In my case it had to do with the nature of how work is done using virt-dma. The virt-dma is predicated on only letting one transaction be active at a time and it increases the latency for getting the next transaction off. For large transactions, it's negligible. But for small transactions, it is pretty evident. > One of the things I am thinking about is the repeated (spin) locking/unlocking > of the virt_dma_chan->lock or vc->lock. In many cases, there's only 1 user or > thread requiring to do a DMA, so I feel the locking is unnecessary and potential > overhead. If there's a sane way to detect this an avoid locking altogether, that > would be great. I'd expect the locking to not be the source of the problem, especially with your use case. [snip] -- sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
