|From:||Ingo Molnar <mingo-AT-elte.hu>|
|To:||Adrian Bunk <bunk-AT-stusta.de>|
|Subject:||Re: [patch 00/2] improve .text size on gcc 4.0 and newer compilers|
|Date:||Mon, 2 Jan 2006 11:37:21 +0100|
|Cc:||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. Ingo
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