|| ||Ingo Molnar <mingo-AT-elte.hu>|
|| ||Adrian Bunk <bunk-AT-stusta.de>|
|| ||Re: [patch 00/2] improve .text size on gcc 4.0 and newer compilers|
|| ||Mon, 2 Jan 2006 11:37:21 +0100|
|| ||Tim Schmielau <tim-AT-physik3.uni-rostock.de>,
Arjan van de Ven <arjan-AT-infradead.org>,
Linus Torvalds <torvalds-AT-osdl.org>,
Dave Jones <davej-AT-redhat.com>, Andrew Morton <akpm-AT-osdl.org>,
lkml <linux-kernel-AT-vger.kernel.org>, mpm-AT-selenic.com|
* Adrian Bunk <firstname.lastname@example.org> wrote:
> My email was about things like Andi's example of the x86-64 vsyscall
> code where we really need inlining, and due to your proposed inline
> semantics change there might be breakages if an __always_inline is
> forgotten at a place where it was required.
we can have two types of breakages:
- stuff wont build if not always_inline. Really easy to find and fix.
- stuff wont work at all (e.g. vsyscalls) because they have some
unspecified reliance on gcc's code output. Such code Is Bad anyway,
and the breakage is still clear: the vsyscalls wont work at all, it's
quickly found, the appropriate always_inline is inserted, and the
incident is forgotten.
talking about 'safer' or 'risky' in this context is misleading, these
are very clear symptoms which are easy to fix.
[ If you didnt talk about this uninline patch in the "we have to wait
one year" comment then please clarify that - all that came through to
me was some vague "lets wait with this" message, and it wasnt clear
(to me) which patch it applied to and why. ]
> Your uninline patch might be simple, but the safe way would be Arjan's
> approach to start removing all the buggy inline's from .c files.
sure, that's another thing to do, but it's also clear that there's no
reason to force inlines in the -Os case.
There are 22,000+ inline functions in the kernel right now (inlined
about a 100,000 times), and we'd have to change _thousands_ of them.
They are causing an unjustified code bloat of somewhere around 20-30%.
(some of them are very much justified, especially in core kernel code)
to say it loud and clear again: our current way of handling inlines is
_FUNDAMENTALLY BROKEN_. To me this means that fundamental changes are
needed for the _mechanics_ and meaning of inlines. We default to 'always
inline' which has a current information to noise ratio of 1:10 perhaps.
My patch changes the mechanics and meaning of inlines, and pretty much
anything else but a change to the meaning of inlines will still result
in the same scenario occuring over and over again.
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