Messages in this thread | | | Date | Thu, 8 Jan 2009 11:26:28 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] ring_buffer: fix ring_buffer_event_length() |
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On Thu, 8 Jan 2009 12:55:30 +0100 Ingo Molnar <mingo@elte.hu> wrote:
> > * Andrew Morton <akpm@linux-foundation.org> wrote: > > > On Wed, 7 Jan 2009 23:58:39 -0500 (EST) Steven Rostedt <rostedt@goodmis.org> wrote: > > > > > kernel/trace/ring_buffer.c | 8 +++++++- > > > > <looks> > > > > heavens, what a lot of inlining. Looks like something from 1997 :) > > > > Prove me wrong! > > > > > > From: Andrew Morton <akpm@linux-foundation.org> > > > > text data bss dec hex filename > > before: 11320 228 8 11556 2d24 kernel/trace/ring_buffer.o > > after: 10592 228 8 10828 2a4c kernel/trace/ring_buffer.o > > You are wrong :-)
Not.
> With x86 defconfig and gcc 4.3.2 i get zero change in size:
With my config and my gcc I see a large change in size. So those `inline' statements in that C file are *wrong*.
> kernel/trace/ring_buffer.o: > > text data bss dec hex filename > 11485 228 8 11721 2dc9 ring_buffer.o.before > 11485 228 8 11721 2dc9 ring_buffer.o.after > > md5: > 55447563cd459bbb02c6234b2544fcc2 ring_buffer.o.before.asm > 55447563cd459bbb02c6234b2544fcc2 ring_buffer.o.after.asm > > (i took out the free_page() bit to only measure the inlining) > > That is the same with and without CONFIG_OPTIMIZE_INLINING - i.e. recent > GCC gets the inlining right. > > Really, we should stop bothering about inlines on the source code level > (the kernel has 20,000 inlines and around 100,000 functions - do we really > want to maintain inlining information on a per function basis?) - and we > should tell the GCC folks when the compiler messes up some detail. > > Or if GCC messes up inlining so much in the future that we cannot live > with it, we can go back to "always inline" and manual annotations again. > Or write a new compiler. (the latter is probably less work ;-)
None of that makes the inline statements in ring_buffer.c less wrong. It says that with some configs and some gcc versions, their damage is lessened.
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