Re: [PATCH-next v2] arm32: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION

[liuyuntao (F)]

On 2024/3/11 17:14, Geert Uytterhoeven wrote:
> Hi Yuntao,
>
> On Sat, Mar 9, 2024 at 2:24 PM liuyuntao (F) <liuyuntao12@xxxxxxxxxx> wrote:
> > On 2024/3/9 16:20, Arnd Bergmann wrote:
> > > On Sat, Mar 9, 2024, at 07:14, liuyuntao (F) wrote:
> > > > On 2024/3/8 21:15, Arnd Bergmann wrote:
> > > > > On Thu, Mar 7, 2024, at 16:12, Yuntao Liu wrote:
> > > >
> > > > Thanks for the tests, CONFIG_LD_DEAD_CODE_DATA_ELIMINATION and
> > > > CONFIG_TRIM_UNUSED_KSYMS do indeed result in a significant improvement.
> > > > I found that arm32 still doesn't support CONFIG_LTO_CLANG. I've done
> > > > some work on it, but without success. I'd like to learn more about the
> > > > CONFIG_LTO_CLANG patch. Do you have any relevant links?
> > >
> > > I did not try to get it to boot and gave up when I did not see
> > > any size improvement. I think there were previous attempts to
> > > do it elsewhere, which I did not try to find.
> >
> > I tested this patch, the size improvement was only about one
> > ten-thousandth, and the compilation time had increased by about a quarter,
> > and the kernel did not boot.
> >
> > Strangely, LTO has actually increased the compilation time
> > significantly, which seems contrary to its purpose.
>
> The purpose of LTO is to reduce code size. Doing so requires more
> processing, hence the total build time increases.
>
> Gr{oetje,eeting}s,
>
>                          Geert

Thanks, Geert, I got it.