Hi, On Sun, May 12, 2019 at 10:59:54PM +0200, Uenal Mutlu wrote: > Increasing the SATA/AHCI DMA TX/RX FIFOs (P0DMACR.TXTS and .RXTS, ie. > TX_TRANSACTION_SIZE and RX_TRANSACTION_SIZE) from default 0x0 each > to 0x3 each, gives a write performance boost of 120 MiB/s to 132 MiB/s > from lame 36 MiB/s to 45 MiB/s previously. > Read performance is about 200 MiB/s. > [tested on SSD using dd bs=2K/4K/8K/12K/16K/24K/32K: peak-perf at 12K]. > > Tested on the Banana Pi R1 (aka Lamobo R1) and Banana Pi M1 SBCs > with Allwinner A20 32bit-SoCs (ARMv7-a / arm-linux-gnueabihf). > These devices are RaspberryPi-like small devices. > > This problem of slow SATA write-speed with these small devices lasts now > for more than 5 years. Many commentators throughout the years wrongly > assumed the slow write speed was a hardware limitation. This patch finally > solves the problem, which in fact was just a hard-to-fix software problem > (b/c of lack of documentation by the SoC-maker Allwinner Technology). > > RFC: Since more than about 25 similar SBC/SoC models do use the > ahci_sunxi driver, users are encouraged to test it on all the > affected boards and give feedback. > > Lists of the affected sunxi and other boards and SoCs with SATA using > the ahci_sunxi driver: > $ grep -i -e "^&ahci" arch/arm/boot/dts/sun*dts > and http://linux-sunxi.org/SATA#Devices_with_SATA_ports > See also http://linux-sunxi.org/Category:Devices_with_SATA_port > > Patch v2: > - Commented the patch in-place in ahci_sunxi.c > - With bs=12K and no conv=... passed to dd, the write performance > rises further to 132 MiB/s > - Changed MB/s to MiB/s > - Posted the story behind the patch: > http://lkml.iu.edu/hypermail/linux/kernel/1905.1/03506.html > - Posted a dd test script to find optimal bs, and some results: > https://bit.ly/2YoOzEM > > Patch v1: > - States bs=4K for dd and a write performance of 120 MiB/s > > Signed-off-by: Uenal Mutlu <um@xxxxxxxxxxx> Acked-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxx> Just a minor nitpick though, the part starting with RFC: and with the version changelog should be after the --- below so that it doesn't get applied as part of the commit log. Maxime -- Maxime Ripard, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
