Messages in this thread | | | Date | Thu, 17 Nov 2022 09:28:00 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 00/46] gcc-LTO support for the kernel |
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On Mon, Nov 14, 2022 at 08:40:50PM +0100, Ard Biesheuvel wrote: > On Mon, 14 Nov 2022 at 12:44, Jiri Slaby (SUSE) <jirislaby@kernel.org> wrote: > > > > Hi, > > > > this is the first call for comments (and kbuild complaints) for this > > support of gcc (full) LTO in the kernel. Most of the patches come from > > Andi. Me and Martin rebased them to new kernels and fixed the to-use > > known issues. Also I updated most of the commit logs and reordered the > > patches to groups of patches with similar intent. > > > > The very first patch comes from Alexander and is pending on some x86 > > queue already (I believe). I am attaching it only for completeness. > > Without that, the kernel does not boot (LTO reorders a lot). > > > > In our measurements, the performance differences are negligible. > > > > The kernel is bigger with gcc LTO due to more inlining. > > OK, so if I understand this correctly: > - the performance is the same > - the resulting image is bigger > - we need a whole lot of ugly hacks to placate the linker. > > Pardon my cynicism, but this cover letter does not mention any > advantages of LTO, so what is the point of all of this?
Seconded; I really hate all the ugly required for the GCC-LTO 'solution'. There not actually being any benefit just makes it a very simple decision to drop all these patches on the floor.
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