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    SubjectRe: [PATCH v4 0/2] kbuild: Cache exploratory calls to the compiler
    2017-10-17 2:12 GMT+09:00 Douglas Anderson <dianders@chromium.org>:
    > This two-patch series attempts to speed incremental builds of the
    > kernel up by a bit. How much of a speedup you get depends a lot on
    > your environment, specifically the speed of your workstation and how
    > fast it takes to invoke the compiler.
    >
    > In the Chrome OS build environment you get a really big win. For an
    > incremental build (via emerge) I measured a speedup from ~1 minute to
    > ~35 seconds. ...but Chrome OS calls the compiler through a number of
    > wrapper scripts and also calls the kernel make at least twice for an
    > emerge (during compile stage and install stage), so it's a bit of a
    > worst case.
    >
    > Perhaps a more realistic measure of the speedup others might see is
    > running "time make help > /dev/null" outside of the Chrome OS build
    > environment on my system. When I do this I see that it took more than
    > 1.0 seconds before and less than 0.2 seconds after. So presumably
    > this has the ability to shave ~0.8 seconds off an incremental build
    > for most folks out there. While 0.8 seconds savings isn't huge, it
    > does make incremental builds feel a lot snappier.
    >
    > Ingo Molnar also did some testing of this in his environment and found
    > that an incremental build of his subsystem sped up from ~.44 seconds
    > before to ~.15 seconds after. Clean builds also sped up by a marginal
    > amount. :)
    >
    > Changes in v4:
    > - Add a mkdir
    > - Point to forward declaration commit by git hash
    >
    > Changes in v3:
    > - Rule to prevent make from trying to generate the cache
    > - Rule to clean .cache.mk
    > - No more doc changes
    > - Moved cache stuff below cc-cross-prefix
    > - Removed duplicate documentation of try-run (oops)
    > - Add Tested-by for Ingo and Guenter since v2 and v3 are very similar
    >
    > Changes in v2:
    > - Abstract at a different level (like shell-cached) per Masahiro Yamada
    > - Include ld-version, which I missed the first time
    >
    > Douglas Anderson (2):
    > kbuild: Add a cache for generated variables
    > kbuild: Cache a few more calls to the compiler
    >
    > Makefile | 5 +--
    > scripts/Kbuild.include | 90 ++++++++++++++++++++++++++++++++++++++++++--------
    > 2 files changed, 79 insertions(+), 16 deletions(-)
    >


    Applied to linux-kbuild/kbuild. Thanks.

    --
    Best Regards
    Masahiro Yamada

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