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SubjectRe: Do we really need SLOB nowdays?
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On 12/15/21 07:29, Hyeonggon Yoo wrote:
> On Tue, Dec 14, 2021 at 06:24:58PM +0100, Vlastimil Babka wrote:
>> On 12/10/21 13:06, Christoph Lameter wrote:
>> > On Fri, 10 Dec 2021, Hyeonggon Yoo wrote:
>> >
>> >> > > (But I still have doubt if we can run linux on machines like that.)
>> >> >
>> >> > I sent you a series of articles about making Linux run in 1MB.
>> >>
>> >> After some time playing with the size of kernel,
>> >> I was able to run linux in 6.6MiB of RAM. and the SLOB used
>> >> around 300KiB of memory.
>> >
>> > What is the minimal size you need for SLUB?
>>
>
> I don't know why Christoph's mail is not in my mailbox. maybe I deleted it
> by mistake or I'm not cc-ed.
>
> Anyway, I tried to measure this again with SLUB and SLOB.
>
> SLUB uses few hundreds of bytes than SLOB.
>
> There isn't much difference in 'Memory required to boot'.
> (interestingly SLUB requires less)
>
> 'Memory required to boot' is measured by reducing memory
> until it says 'System is deadlocked on memory'. I don't know
> exact reason why they differ.
>
> Note that the configuration is based on tinyconfig and
> I added initramfs support + tty layer (+ uart driver) + procfs support,
> + ELF binary support + etc.
>
> there isn't even block layer, but it's good starting point to see
> what happens in small system.
>
> SLOB:
>
> Memory required to boot: 6950K
>
> Slab: 368 kB
>
> SLUB:
> Memory required to boot: 6800K
>
> Slab: 552 kB
>
> SLUB with slab merging:
>
> Slab: 536 kB

168kB different on a system with less than 8MB memory looks rather
significant to me to simply delete SLOB, I'm afraid.

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