Messages in this thread | | | Date | Sun, 11 May 2008 19:52:22 +0200 | From | Sam Ravnborg <> | Subject | Re: [2.6 patch] kernel/sched*: optimize inlining |
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On Sun, May 11, 2008 at 12:21:32PM +0300, Adrian Bunk wrote: > kernel/sched* contained tons of inline's, and the result of removing > them all is impressing (with x86_64_defconfig) > text data bss dec hex filename > 39557 8234 280 48071 bbc7 kernel/sched.o > 41792 8234 280 50306 c482 kernel/sched.o.old > > That's a 5.3% text size reduction (!), which is more than twice as much > as the 2.3% the "optimized inlining" achieves on average for the whole > kernel.
If we compare the size of sched.o in the three cases we see a clear effect:
text data bss dec hex filename forced inline: 31257 2702 200 34159 856f kernel/sched.o inline hint: 31105 2702 200 34007 84d7 kernel/sched.o no inline (hint): 30704 2702 200 33606 8346 kernel/sched.o
The last line "no inline(hint)" is with Adrians patch applied. So what is obvious from the above is that with the arch/gcc combination I use here the inline hint has a clear effect and gcc inlines more when we have given it a hint to do so than without the hint. I conclude this solely on the cide size change between the line "inline hint" and "no inline(hint)".
With adrians patch there were no difference in size with or without the OPTIMIZE_INLINING enabled.
Or in other words the config option "OPTIMIZE_INLINING" is NOT equal to removing all the inline annotations.
> > Note that any remarks regarding whether this patch might affect the > performance are invalid since noone cared about the performance when > the "x86: add optimized inlining" commit that does the same for the > whole kernel entered the tree.
In one case it was an option it was easy to turn off/on so we could compare and modulus bugs it was a noop on gcc < 4.0. With the patch below we revet back to the broken gcc inline algorithm on gcc < 4.0 and it cannot as easy be turned of (have to revert this patch). Both issues are worth to consider before applying this.
Sam
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