| Date | Mon, 20 Aug 2012 09:48:35 +0200 | From | Ingo Molnar <> | Subject | Re: RFC: Link Time Optimization support for the kernel |
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* Andi Kleen <andi@firstfloor.org> wrote:
> This rather large patchkit enables gcc Link Time Optimization (LTO) > support for the kernel. > > With LTO gcc will do whole program optimizations for > the whole kernel and each module. This increases compile time, > but can generate faster code.
By how much does it increase compile time?
How much faster does kernel code get?
Last time I checked LTO optimizations (half a year ago) it resulted in significantly slower build times.
I tried out and measured the LTO speedups and was less than impressed by them - a lot of build time increase for not much increase in performance. There was also visible, ongoing maintenance cost.
The combination of these seemed like a show-stopper.
It's obviously an optimization feature we should consider, but we really need hard numbers to make a cost/benefit analysis.
Thanks,
Ingo
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