Re: [PATCH v2 37/59] x86/putuser: Provide room for padding

[Linus Torvalds]

On Fri, Sep 2, 2022 at 1:25 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> The below (mashup of a handful of patches) is the best I could come up
> with in a hurry.

Hmm. It doesn't look too horrible, but yeah, fi it still ends up
getting the same padding overhead I'm not sure it ends up really
mattering.

I was hoping that some of the overhead would just go away - looking at
my kernel build, we do have a fair number of functions that are 1-31
bytes (according to a random and probably broken little shell script:

    objdump -t vmlinux |
        grep 'F .text' |
        sort |
        cut -f2- |
        grep '^00000000000000[01]'

but from a quick look, a fair number of them aren't actually even leaf
functions (ie they are small because they just call another function
with a set of simple arguments, often as a tail-call).,

So maybe it's just not worth it.

> If this patch makes you feel warm and fuzzy, I can clean it up,
> otherwise I would suggest getting the stuff we have merged before adding
> even more things on top.

Yeah, it doesn't look that convincing.  I have no real numbers - a lot
of small functions, but I'm not convinced that it is worth worrying
about them, particularly if it doesn't really help the actual text
size.

              Linus