Messages in this thread | | | Subject | Re: [PATCH v8 02/21] acpi: fix acpi_os_ioremap for arm64 | From | David Woodhouse <> | Date | Wed, 04 Feb 2015 16:38:59 +0000 |
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On Wed, 2015-02-04 at 16:25 +0000, Russell King - ARM Linux wrote: > I haven't experimented with it myself, but I think David Woodhouse > has some experience in this area.
In many kernel configurations there are actually quite a lot of functions that are never called, and I was quite surprised the first time I played with this stuff.
There are a few ways of dealing with it. One is to use -ffunction-section -fdata-sections --gc-sections as you noted. I once also played with using GCC's --combine during the brief period that it was supported and not *entirely* broken, with similar effects: https://lwn.net/Articles/197097/
These days, the better answer is probably LTO. We could potentially still look at --gc-sections, but I suspect we're better off using LTO and just filing toolchain bugs until everything that --gc-sections *would* have dropped is also dropped from the LTO build :)
Unless --gc-sections actually speeds up the build in a significant way; a full LTO link of the kernel takes insane amounts of memory IIRC.
-- David Woodhouse Open Source Technology Centre David.Woodhouse@intel.com Intel Corporation [unhandled content-type:application/x-pkcs7-signature] | |