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Date: Wed, 13 May 2020 16:27:38 +0500 From: "Artem S. Tashkinov" <aros@....com> To: Jason@...c4.com Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: [PATCH] Kconfig: default to CC_OPTIMIZE_FOR_PERFORMANCE_O3 for gcc >= 10 > GCC 10 appears to have changed -O2 in order to make compilation time faster when using -flto, seemingly at the expense of performance, in particular with regards to how the inliner works. Since -O3 these days shouldn't have the same set of bugs as 10 years ago, this commit defaults new kernel compiles to -O3 when using gcc >= 10. It's a strong "no" from me. 1) Aside from rare Gentoo users no one has extensively tested -O3 with the kernel - even Gentoo defaults to -O2 for kernel compilation 2) -O3 _always_ bloats the code by a large amount which means both vmlinux/bzImage and modules will become bigger, and slower to load from the disk 3) -O3 does _not_ necessarily makes the code run faster 4) If GCC10 has removed certain options for the -O2 optimization level you could just readded them as compilation flags without forcing -O3 by default on everyone 5) If you still insist on -O3 I guess everyone would be happy if you just made two KConfig options: OPTIMIZE_O2 (-O2) OPTIMIZE_O3_EVEN_MOAR (-O3) Best regards, Artem
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