On Mon, Feb 24, 2014 at 02:50:28PM -0600, Andy Gross wrote: > 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.
Wrong. virt-dma allows you to fire off the next transaction in the queue immediately that the previous transaction has finished. I know this, because sa11x0-dma does exactly that. You don't need to wait for the tasklet to be called before starting the next transaction. -- FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly improving, and getting towards what was expected from it. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
