Re: [PATCH v3 0/3] Add support for compiling with -ffunction-sections -fdata-sections

[Masami Hiramatsu <mhiramat@redhat.com>]

Tim Abbott wrote:
> On Mon, 20 Apr 2009, Linus Torvalds wrote:
> 
>> I'd be ok with merging it, but I haven't really gotten a strong feeling 
>> that anybody is going to enable it or use it.
> 
> Linus,
> 
> Would you be willing to merge the first 3 patches in this patch series at 
> this point?  I'm resending these patches to resolve some conflicts that 
> was recently introduced.

Hi Tim,

What would you think about posting these patches plus -ffunction-sections/
-fdata-sections patch to -mm tree, -tip tree, or -next tree as
"playable" Ksplice patchset?

If people use it and see it enough stable and useful, those patches
will be automatically pulled into linus kernel.


> To summarize the discussion, there are three uses for this code that have 
> significant interest.
> 
> One is decreasing the kernel size.  Denys Vlasenko has numbers that using 
> the linker's --gc-sections option (for which these patches are a 
> prerequisite) saves 10% of the kernel size when CONFIG_MODULES=n, and 1% 
> when CONFIG_MODULES=y.  Paul Mundt thinks many embedded users would use 
> this if it were available.
> 
> A related use is cleaning up a lot of ifdefs that exist only to decrease 
> the kernel size.  Several developers commented favorably on the direction 
> of using section garbage collection for dead code removal.
> 
> Finally, Ksplice depends on the option added by this patch series.
> 
> The first 3 patches in this patch series fix problems associated with 
> using -ffunction-sections.  As there are some architectures currently 
> using -ffunction-sections, these should ideally be merged now, especially 
> the first patch which involves scattered changes.

If there are actual problems on those arch, I think you'd better post
these patches as bugfixes with bug reports.

Thank you,

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com