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

Mathias Adam m.adam--openwrt at adamis.de
Wed Sep 10 17:18:32 EDT 2014

Hi again Felix,

Am Di, 9.09.2014, 22:20 schrieb Mathias Adam:
> 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?

ImageBuilder seems not to have make target menuconfig... is there another
official way to configure it on ImageBuilder?

Regarding subtarget: is there a rule on specific device properties whether
a device fits generic, or legacy?

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