littlefs port to Lua RTOS ESP32, right configuration?

[jolivepetrus]

Hi guys,

From the Whitecat Team we recently added support for littlefs in our Lua RTOS for the ESP32 soc. Can any one recommend the block_size, read_size, and write_size for a Winbond Flash?

The reason is that for our current configuration it seems that writes are slower that the SPIFFS ones, and as far I can read, littlefs performance is better.

Our current configuration is:

block size = 4096
read size = 1024
prog size = 1024

If anyone it's interested in the port you can find it at:

https://github.com/whitecatboard/Lua-RTOS-ESP32/blob/master/components/sys/vfs/lfs.c

Thanks in advance!

[geky]

Thanks for sharing! It's exciting to see littlefs getting adopted.

You may actually want to try reducing the read size / prog size. I found that ~64B is an optimal value for 4KiB-erase-size NOR flash chips (tested on the MX25R).

littlefs's caches are fairly dumb, so if it only needs to read a small value, it will still read an entire cache line (prog/read size). This means that larger caches can end up costing you, which is a bit counterintuitive. (Fixing this in 2.0 with with a separate cache size option + smarter caching).

Though I wouldn't be surprised if SPIFFS is faster in certain situations. SPIFFS and littlefs have very different approaches.

Most notably, I think SPIFFS will outperform littlefs if erases are much much slower than the storage's bus speed. (There's also several improvements on this in 2.0, such as static wear-leveling in metadata pairs).

[ajaybhargav]

For winbond flash of 8M (4K erase block) I found following numbers to be best working:

Read size = 128
Prog size = 256
Lookahead = 256 -> kept for 8M size you can adjust based on size you're using.