Re: [PATCH v3 5/6] powerpc/64: Add support for out-of-line static calls

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 06/10/2022 à 22:45, Segher Boessenkool a écrit :
> On Thu, Oct 06, 2022 at 06:38:00PM +0000, Christophe Leroy wrote:
>> Le 06/10/2022 à 20:22, Segher Boessenkool a écrit :
>>> Long ago I built kernels that fit together with the boot firmware and a
>>> root fs (busybox+dropbear essentially) in 4MB, but I doubt we can get
>>> close to that at all these days :-)
>>
>> 4MB, not easy. But 8M still achievable. Well our smaller board has 32M,
>> we have thousands of it spread all over Europe and have to keep it up to
>> date ....
> 
> The smallest of these systems had 256MB RAM.  This 4MB is flash ROM :-)

I fit Uboot + DTB + Kernel + Initramfs with klibc and mtdutils in a 2MB 
flash ROM.

> 
>>> What is the overhead if you enable modules but do not use them, these
>>> days?
>>
>> On the 8xx it is mainly the instruction TLB miss handler:
> 
> I meant just an indicative code size number...  100 bytes, 100kB, 100MB,
> or something like that :-)  And, on 64 bit, which is what the question
> was about!

Ah, does the size really matters here ? I was thinking more in terms of 
performance when I made the comment.

Christophe