[OpenWrt-Devel] [PATCH] config: enable some useful features on !SMALL_FLASH devices

[Petr Štetiar]

Daniel Golle <daniel at makrotopia.org> [2019-01-01 17:56:25]:

Hi,

> On Sun, Dec 30, 2018 at 11:26:58AM +0100, Petr Štetiar wrote:
> > Daniel Golle <daniel at makrotopia.org> [2018-12-29 06:51:32]:
> > 
> > >  config KERNEL_AIO
> > >  config KERNEL_FHANDLE
> > >  config KERNEL_FANOTIFY
> > > +	default y if !SMALL_FLASH
> > 
> > What about `FEATURES += nas` to make it clear and don't abuse SMALL_FLASH.
> 
> This is not necessarily only used on NAS devices. systemd requires
> FHANDLE and FANOTIFY (eg. when running inside LXC container), lvm2
> needs AIO. Both could well run on a modern router or SBC having USB or
> an SDCARD slot.

to me it's still just NAS and container use cases. I'm afraid, that adding
more bloat to kernels for devices with USB and MMC/SD card slots would be
rejected also.

> > >  config KERNEL_CGROUPS
> > >  config KERNEL_CPUSETS
> > >  config KERNEL_CGROUP_CPUACCT
> > >  config KERNEL_RESOURCE_COUNTERS
> > >  config KERNEL_MEMCG
> > >  config KERNEL_MEMCG_KMEM
> > >  menuconfig KERNEL_CGROUP_SCHED
> > >   config KERNEL_FAIR_GROUP_SCHED
> > >   config KERNEL_RT_GROUP_SCHED
> > >  config KERNEL_NAMESPACES
> > >  config KERNEL_LXC_MISC
> > >  config KERNEL_SECCOMP_FILTER
> > >  config KERNEL_SECCOMP
> > > -		default n
> > > +		default y if !SMALL_FLASH
> > 
> > What about `FEATURES += containers` ?
> 
> From what I understood FEATURES is supposed to reflect hardware
> capabilities

Well, almost. I've found `squashfs` and `ext4` in there also.

>  -- all the above are generic software features useful on any device having
>  the capacity (ie. flash and RAM) to make use of them.

But as other Daniel already suggested, !SMALL_FLASH isn't proper group
selection either. Speaking about the capacity, did you measured how much those
features add to the kernel images?

> > Daniel Engberg <daniel.engberg.lists at pyret.net> [2018-12-30 10:21:46]:
> > 
> > > however KERNEL_CGROUPS, config KERNEL_NAMESPACES, config KERNEL_LXC_MISC,
> > > KERNEL_SECCOMP_FILTER are very limited use cases to my knowledge and more or
> > > less only used on x86*?
> > 
> > There are other quite powerful platforms like mvebu, imx6, ipq etc. where you
> > could use this as well.
> 
> I use LXC on oxnas/ox820 (ARM11mpcore) and ramips/mt7621 (MIPS1004Kc),

Ok, looking at IMAGE_SIZE values for mt7621 yields following results:

 IMAGE_SIZE := 6016k                         TP-LINK RE350 v1
 IMAGE_SIZE := 7798784                       I-O DATA WN-GX300GR
 IMAGE_SIZE := $(ralink_default_fw_size_4M)  MT7621 EVB
 IMAGE_SIZE := $(ralink_default_fw_size_8M)  AP-MT7621A-V60 EVB

So it wouldn't be wise to add more bloat into kernels for those devices.

> running Debian inside LXC containers (and it's annoying that I can't
> use regular OpenWrt releases or buildbot-generated snapshots on the).

I would like to do the same, but on the other hand I also understand, why your
patch as it is wouldn't be accepted. Our containers/NAS use cases are still
very rare, thus it makes no sense to enable those features by default to every
other !SMALL_FLASH target. As you can see on mt7621, it's not marked as
SMALL_FLASH, yet there are devices which might be considered SMALL_FLASH.

Now I realize, that it couldn't be handled with FEATURES anyway, as this is
always too broad group selection and ideally you want to enable those features
for specific devices only, meaning different kernels, images etc.

-- ynezz

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