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    SubjectRe: [PATCH 06/22] kbuild: lto: limit inlining
    On Wed, Jun 24, 2020 at 01:31:44PM -0700, Sami Tolvanen wrote:
    > This change limits function inlining across translation unit
    > boundaries in order to reduce the binary size with LTO.
    >
    > The -import-instr-limit flag defines a size limit, as the number
    > of LLVM IR instructions, for importing functions from other TUs.
    > The default value is 100, and decreasing it to 5 reduces the size
    > of a stripped arm64 defconfig vmlinux by 11%.

    Is that also the right number for x86? What about the effect on
    performance? What did 6 do? or 4?

    > Suggested-by: George Burgess IV <gbiv@google.com>
    > Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
    > ---
    > Makefile | 4 ++++
    > 1 file changed, 4 insertions(+)
    >
    > diff --git a/Makefile b/Makefile
    > index 3a7e5e5c17b9..ee66513a5b66 100644
    > --- a/Makefile
    > +++ b/Makefile
    > @@ -894,6 +894,10 @@ else
    > CC_FLAGS_LTO_CLANG := -flto
    > endif
    > CC_FLAGS_LTO_CLANG += -fvisibility=default
    > +
    > +# Limit inlining across translation units to reduce binary size
    > +LD_FLAGS_LTO_CLANG := -mllvm -import-instr-limit=5
    > +KBUILD_LDFLAGS += $(LD_FLAGS_LTO_CLANG)
    > endif
    >
    > ifdef CONFIG_LTO
    > --
    > 2.27.0.212.ge8ba1cc988-goog
    >

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