On 27 June 2011 12:02, Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > On Mon, Jun 27, 2011 at 11:42:52AM +0200, Per Forlin wrote: >> Conclusion: >> Working with mmc the relative cost of DSB is almost none. There seems >> to be slightly higher number for mmc blocking requests with the DSB >> patch compared to not having it. > > These figures suggest that dsb is comparitively not heavy on the hardware > you're testing. > Yes, of course. > I think I'm going to apply the patch anyway - it certainly makes stuff > no worse, and if someone has a platform where dsb is more expensive, > then they should see a greater benefit from this change. > I agree. > The next thing to think about in DMA-land is whether we should total up > the size of the SG list and choose whether to flush the individual SG > elements or do a full cache flush. There becomes a point where the full > cache flush becomes cheaper than flushing each SG element individually. > Interesting. I have seen such optimisations in hwmem (yet another memory manager for multi media hardware). It would be nice to have such functionality in dma-mapping, to be used by anyone Regards, Per -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
