On Wed, Oct 4, 2017 at 3:37 PM, Douglas Anderson <dianders@xxxxxxxxxxxx> wrote: > 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. > > Caveats from v1 still copied here, though with Masahiro Yamada's > suggestions from v1 this is starting to feel a little more baked and > I've even dropped the RFC from it (though extra testing still > appreciated): > > Please note that I make no illusions of being a Makefile expert nor do > I have any belief that I fully understand the Linux kernel build > system. Please take this patch series as the start of a discussion > about whether others feel like this type of speedup is worthwhile and > how to best accomplish it. Specific things to note: > > - I'm happy to paint the bikeshed any color that maintainers want. If > you'd like the cache named differently, in a slightly different > format, or you want me to adjust the spacing / names of Makefile > stuff then please just let me know. > > - If this is totally the wrong approach and you have a better idea > then let me know. If you want something that's super complicated to > explain then feel free to post a replacement patch and I'm happy to > test. > > - This patch definitely needs extra testing. I've tested it on a very > limited build environment and it seems to be working fine, but I > could believe that with some weird compiler options or on certain > architectures you might need some extra escaping here and there. > Not being a makefile expert, I can't say anything about the merits of this series. However, it does pass a run on my test farm at kerneltests.org. So. I'll give it a Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx> Guenter > 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 > > Documentation/kbuild/makefiles.txt | 21 +++++++++ > Makefile | 4 +- > scripts/Kbuild.include | 90 ++++++++++++++++++++++++++++++++------ > 3 files changed, 99 insertions(+), 16 deletions(-) > > -- > 2.14.2.920.gcf0c67979c-goog > -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
