[PATCH 1/1] mmc: Set optimal I/O size when mmc_setip_queue

[Shawn Lin]

Hi Sharp

On 2023/8/27 0:26, Sharp.Xia at mediatek.com 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.

> 
> I tested with RK3568 and sdhci-of-dwcmshc.c driver, the performance improved by 2~3%.
>   
> Before:
> root at 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 at OpenWrt:/mnt/mmcblk0p3# cat /sys/block/mmcblk0/queue/read_ahead_kb
> 128
>   
> After:
> root at OpenWrt:/mnt/mmcblk0p3# echo 3 > /proc/sys/vm/drop_caches
> root at 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 at OpenWrt:/mnt/mmcblk0p3# cat /sys/block/mmcblk0/queue/read_ahead_kb
> 1024
>   
> root at 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)
>