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Date: Fri, 12 Jun 2020 09:57:20 +0200
From: Mikhail Morfikov <>
Subject: Re: RE: ISRA optimized functions

On 12/06/2020 00:19, Adam Zabrocki wrote:
> I would need to do manual investigation how your build process looks and works. 
> However, I don't think it makes any sense.

Actually it's not just my build process, only the kernel's bindeb-pkg target 
which I think all people using Debian call when they're building their custom 
kernels. It produces simple deb packages that can be installed via 
apt-get/aptitude to make the system clean when you don't need them anymore. So
this is quite common technique to build the kernel, at least on Debian/Ubuntu.

> However, which function would be affected by such optimization purely 
> depends on the kernel configuration.

I have a question. There's "Compiler optimization level" in the kernel config 
with the following options to choose:

This is the default optimization level for the kernel, building
with the "-O2" compiler flag for best performance and most
helpful compile-time warnings.

Choosing this option will pass "-Os" to your compiler resulting
in a smaller kernel.

So either one is used with the default to CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE. 
Maybe this is the problem with "-O2"? If so, it's default and I don't think this 
"-O2" flag can be removed without changing kernel distro config, which I don't 
think is likely to happen. The following is from the Debian default kernel 

$ grep CONFIG_CC_OPTIMIZE /boot/config-5.6.0-2-amd64

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