On Mon, 28 Aug 2023 at 04:28, Shawn Lin <shawn.lin@xxxxxxxxxxxxxx> wrote: > > Hi Sharp > > On 2023/8/27 0:26, Sharp.Xia@xxxxxxxxxxxx wrote: > > On Fri, 2023-08-25 at 17:17 +0800, Shawn Lin wrote: > >> > >> > > After more testing, most of my platforms which runs at HS400/HS200 mode > shows nearly no differences with the readahead ranging from 128 to 1024. > Yet just a board shows a performance drop now. Highly suspect it's eMMC > chip depends. I would recommand leave it to the BSP guys to decide which > readahead value is best for their usage. That's a very good point. The SD/eMMC card certainly behaves differently, depending on the request-size. Another thing we could consider doing, could be to combine the information about the request-size from the mmc host, with some relevant information from the registers in the card (not sure exactly what though). > > > > > I tested with RK3568 and sdhci-of-dwcmshc.c driver, the performance improved by 2~3%. > > > > Before: > > root@OpenWrt:/mnt/mmcblk0p3# time dd if=test.img of=/dev/null > > 2097152+0 records in > > 2097152+0 records out > > real 0m 6.01s > > user 0m 0.84s > > sys 0m 2.89s > > root@OpenWrt:/mnt/mmcblk0p3# cat /sys/block/mmcblk0/queue/read_ahead_kb > > 128 > > > > After: > > root@OpenWrt:/mnt/mmcblk0p3# echo 3 > /proc/sys/vm/drop_caches > > root@OpenWrt:/mnt/mmcblk0p3# time dd if=test.img of=/dev/null > > 2097152+0 records in > > 2097152+0 records out > > real 0m 5.86s > > user 0m 1.04s > > sys 0m 3.18s > > root@OpenWrt:/mnt/mmcblk0p3# cat /sys/block/mmcblk0/queue/read_ahead_kb > > 1024 > > > > root@OpenWrt:/sys/kernel/debug/mmc0# cat ios > > clock: 200000000 Hz > > actual clock: 200000000 Hz > > vdd: 18 (3.0 ~ 3.1 V) > > bus mode: 2 (push-pull) > > chip select: 0 (don't care) > > power mode: 2 (on) > > bus width: 3 (8 bits) > > timing spec: 9 (mmc HS200) > > signal voltage: 1 (1.80 V) > > driver type: 0 (driver type B) > > Thanks for testing and sharing the data, both of you! Kind regards Uffe
