(+LLVM list, Fangrui Song) On Fri, Jun 17, 2022 at 7:41 PM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote: > > On Fri, Jun 17, 2022 at 12:35 PM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote: > > > > On Fri, Jun 17, 2022 at 12:53 AM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote: > > > > > > On Thu, Jun 16, 2022 at 4:09 PM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote: > > > > > > > > On Thu, Jun 16, 2022 at 12:45 PM Jiri Slaby <jslaby@xxxxxxx> wrote: > > > > > > > > > > Until the link-vmlinux.sh split (cf. the commit below), the linker was > > > > > run with jobserver set in MAKEFLAGS. After the split, the command in > > > > > Makefile.vmlinux_o is not prefixed by "+" anymore, so this information > > > > > is lost. > > > > > > > > > > Restore it as linkers working in parallel (esp. the LTO ones) make a use > > > > > of i Hi Jiri, Please let me clarify first. Here, is it OK to assume you are talking about Clang LTO instead of GCC LTO because the latter is not upstreamed ? I tested this patch but I did not see any performance change for Clang LTO. [1] CONFIG_CLANG_LTO_FULL lld always runs sequential. It never runs in parallel even if you pass -j option to Make [2] CONFIG_CLANG_LTO_THIN lld always runs in parallel even if you do not pass -j option In my machine, lld always allocated 12 threads. This is irrespective of the Make parallelisms. One more thing, if a program wants to participate in Make's jobserver, it must parse MAKEFLAGS, and extract file descriptors to be used to communicate to the jobserver. As a code example in the kernel tree, scripts/jobserver-exec parses "MAKEFLAGS" and "--jobserver". I grepped the lld source code, but it does not contain "MAKEFLAGS" or "jobserver". masahiro@oscar:~/ref/lld$ git remote show origin * remote origin Fetch URL: https://github.com/llvm-mirror/lld.git Push URL: https://github.com/llvm-mirror/lld.git HEAD branch: master Remote branches: master tracked release_36 tracked release_37 tracked release_38 tracked release_39 tracked release_40 tracked release_50 tracked release_60 tracked release_70 tracked release_80 tracked release_90 tracked Local branch configured for 'git pull': master merges with remote master Local ref configured for 'git push': master pushes to master (up to date) masahiro@oscar:~/ref/lld$ git grep MAKEFLAGS masahiro@oscar:~/ref/lld$ git grep jobserver So, in my research, LLD does not seem to support the jobserver. If you are talking about GCC LTO, yes, the code tries to parse "--jobserver-auth=" from the MAKEFLAGS environment variable. [1] [1]: https://github.com/gcc-mirror/gcc/blob/releases/gcc-12.1.0/gcc/lto-wrapper.cc#L1341 But, as you may know, GCC LTO works in a different way, at least, we cannot do it before modpost. -- Best Regards Masahiro Yamada
