Deprecating and removing SLOB

[Janusz Krzysztofik]

On Wednesday, 9 November 2022 16:50:08 CET Aaro Koskinen wrote:
> Hi,
>
> On Wed, Nov 09, 2022 at 10:00:25AM +0100, Vlastimil Babka wrote:
> > > On Tue, Nov 8, 2022 at 10:55 AM Vlastimil Babka <vbabka at suse.cz> wrote:
> > >> I believe SLOB can be removed because:
> > >>
> > >> - AFAIK nobody really uses it? It strives for minimal memory footprint
> > >> by putting all objects together, which has its CPU performance costs
> > >> (locking, lack of percpu caching, searching for free space...). I'm not
> > >> aware of any "tiny linux" deployment that opts for this. For example,
> > >> OpenWRT seems to use SLUB and the devices these days have e.g. 128MB
> > >> RAM, not up to 16 MB anymore. I've heard anecdotes that the performance
> > >> SLOB impact is too much for those who tried. Googling for
> > >> "CONFIG_SLOB=y" yielded nothing useful.
> > >
> > > I am all for removing SLOB.
> > >
> > > There are some devices with configs where SLOB is enabled by default.
> > > Perhaps, the owners/maintainers of those devices/configs should be
> > > included into this thread:
>
> [...]
>
> > > arch/arm/configs/omap1_defconfig:CONFIG_SLOB=y
>
> I have been using SLUB on my OMAP1 boards with 32 MB RAM, because of
> better debugging features and the memory footprint difference doesn't
> really matter for my use cases. Looking at history why SLOB was added
> there, it seems it came from 6cfce27c14aa ("omap1: Add omap1_defconfig")
> when separate boards configs were merged, and SX1 board happened to have
> SLOB in there. This board is nowadays only used in QEMU anyway.
>
> There are OMAP1 boards with only 16 MB, but support for those boards
> will be removed. So from OMAP1 side, I don't think there is any real
> need for SLOB anymore.

Moreover, I always had issues with availability of socket buffers during USB
device setup when trying to use SLOB on Amstrad Delta based on OMAP1510,
the least powerful OMAP1.  Then, +1 for SLOB removal.

Thanks,
Janusz