Messages in this thread | | | Date | Mon, 13 Apr 2015 18:23:08 +0200 | From | Markus Trippelsdorf <> | Subject | Re: [PATCH] x86: Align jump targets to 1 byte boundaries |
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On 2015.04.12 at 12:14 +0200, Ingo Molnar wrote: > In my (past) experience the main win from -flto is not due to better > hot/cold decisions, but simply due to more aggressive dead code > elimination. -flto has less of an effect on code that is actually > being executed. > > Which isn't to be sneered at, but it's far less of a direct effect as > branch probabilities are, which cut to the core of most hotpaths in > the kernel.
I did some measurements with gcc-5.1-RC on X86_64 using Andi's latest LTO kernel patch for 4.0. With my simple monolithic .config the code size savings are below 1%. That is lower than I've expected.
-- Markus
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