[OpenWrt-Devel] [PATCH] config: extend small_flash feature

[Alex Maclean]

On 01/06/18 12:34, Lucian Cristian wrote:

> On 30.05.2018 20:22, Martin Tippmann wrote:
>> find /usr |
>> xargs md5sum
>
> I made the test on tl-wr841n-v9 with luci selected
>
> these are the changes to squashfs
>
> --- a/config/Config-images.in
> +++ b/config/Config-images.in
> @@ -149,8 +149,15 @@ menu "Target Images"
>                         int "Block size (in KiB)"
>                         depends on TARGET_ROOTFS_SQUASHFS
>                         default 64 if LOW_MEMORY_FOOTPRINT
> +                       default 1024 if (SMALL_FLASH &&
> !LOW_MEMORY_FOOTPRINT)
>                         default 256
>
> +               config SQUASHFS_FRAGMENT_CACHE_SIZE
> +                       int "Number of fragments cached"
> +                       depends on TARGET_ROOTFS_SQUASHFS
> +                       default 1 if (SMALL_FLASH &&
> !LOW_MEMORY_FOOTPRINT)
> +                       default 3
> +
>         menuconfig TARGET_ROOTFS_UBIFS
>                 bool "ubifs"
>                 default y if USES_UBIFS

This won't have actually changed the option - you should use
KERNEL_SQUASHFS_FRAGMENT_CACHE_SIZE,
and CONFIG_SQUASHFS_EMBEDDED=y is also needed in the kernel config.
I think this also therefore belongs either in Config-kernel.in or simply
in the subtarget kernel config.

I did a few tests myself:

256K and 3 fragments:
10608K used after boot, 11408K free after reading /usr
24.5 seconds from kernel start to wifi link up

1024K and 3 fragments:
14520K after boot, 15204K after reading
30 seconds to link up

1024K and 2 fragments:
13460K after boot, 14128K after reading
34.7 seconds to link up

1024K and 1 fragment:
11620K after boot, 12364K after reading
46.8 seconds to link up

Certainly quite a lot of memory impact with the larger block size, but
also a quite significant performance impact with the larger reads.

I'm leaning towards compromising on 2 fragments but I'd like input on that.

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