[OpenWrt-Devel] Increase default squashfs blocksize for devices with small flash?

Mathias Adam m.adam--openwrt at adamis.de
Tue Sep 9 16:20:43 EDT 2014

Hi Felix,

Am Di, 9.09.2014, 21:32 schrieb Felix Fietkau:
> On 2014-09-09 21:21, Mathias Adam wrote:
>> Hi,
>> just noticed that the pre-built image for Huawei E970 (brcm47xx-legacy,
>> openwrt-e970-squashfs-gz.bin) is too large for its 4MiB flash.
>> This is true for both BB-rc3 and trunk snapshots.
>> Apparently Imagebuilder creates squashfs with 64kiB blocksize. However I
>> usually used 256kiB or even 1MiB on this device, which in my experience
>> saves some 100kiB.
>> Up to now I mostly used trunk builds; now I was able to create working
>> images with ImageBuilder as well after manually changing .config.
>> What is the recommended way to deal with this?
>> E.g. is it possible to set squashfs blocksize in a profile?
> It's not possible to set it in a profile. You can change it via make
> menuconfig, but keep in mind that increasing the block size will
> significantly increase RAM usage. That's the main reason why
> brcm47xx-legacy uses a smaller block size than other targets.

I see. I assumed squashfs needs some more RAM with larger blocks size, but
didn't actually measure it so far. Though I haven't experienced short RAM
issues so far on E970, at least it has 32M. Flash size was always my
biggest concern on that device. (I stopped using a WRT54 some time before
because of constant hassle with its only 16M RAM...)

So maybe it would make sense to move it to generic?
However that would include more variants in b43 -- or is it possible to
remove unnecessary b43 PHY variants in a profile?

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