On Mon, Dec 21, 2015 at 11:28:15AM +0100, Ulf Hansson wrote: > On 19 December 2015 at 21:30, Russell King <rmk+kernel@xxxxxxxxxxxxxxxx> wrote: > > Unnecessarily mapping and unmapping the align buffer for SD cards is > > expensive: performance measurements on iMX6 show that this gives a hit > > of 10% on hdparm buffered disk reads. > > > > MMC/SD card IO comes from the mm/vfs which gives us page based IO, so > > for this case, the align buffer is not going to be used. However, we > > still map and unmap this buffer. > > What about the SDIO case? How will this change affect SDIO data transfers? I can't quantify that as I have no SDIO cards to do any measurements. It depends entirely on the expense of accessing to DMA coherent memory compared to accessing normal memory and then syncing it. -- RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net. -- 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
