Hi Sedat, On Tue, May 5, 2020 at 1:25 AM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote: > > On Mon, May 4, 2020 at 5:13 AM Nick Desaulniers > <nick.desaulniers@xxxxxxxxx> wrote: > > > > As debug information gets larger and larger, it helps significantly save > > the size of vmlinux images to compress the information in the debug > > information sections. Note: this debug info is typically split off from > > the final compressed kernel image, which is why vmlinux is what's used > > in conjunction with GDB. Minimizing the debug info size should have no > > impact on boot times, or final compressed kernel image size. > > > > All of the debug sections will have a `C` flag set. > > $ readelf -S <object file> > > > > $ bloaty vmlinux.gcc75.compressed.dwarf4 -- \ > > vmlinux.gcc75.uncompressed.dwarf4 > > > > FILE SIZE VM SIZE > > -------------- -------------- > > +0.0% +18 [ = ] 0 [Unmapped] > > -73.3% -114Ki [ = ] 0 .debug_aranges > > -76.2% -2.01Mi [ = ] 0 .debug_frame > > -73.6% -2.89Mi [ = ] 0 .debug_str > > -80.7% -4.66Mi [ = ] 0 .debug_abbrev > > -82.9% -4.88Mi [ = ] 0 .debug_ranges > > -70.5% -9.04Mi [ = ] 0 .debug_line > > -79.3% -10.9Mi [ = ] 0 .debug_loc > > -39.5% -88.6Mi [ = ] 0 .debug_info > > -18.2% -123Mi [ = ] 0 TOTAL > > > > $ bloaty vmlinux.clang11.compressed.dwarf4 -- \ > > vmlinux.clang11.uncompressed.dwarf4 > > > > FILE SIZE VM SIZE > > -------------- -------------- > > +0.0% +23 [ = ] 0 [Unmapped] > > -65.6% -871 [ = ] 0 .debug_aranges > > -77.4% -1.84Mi [ = ] 0 .debug_frame > > -82.9% -2.33Mi [ = ] 0 .debug_abbrev > > -73.1% -2.43Mi [ = ] 0 .debug_str > > -84.8% -3.07Mi [ = ] 0 .debug_ranges > > -65.9% -8.62Mi [ = ] 0 .debug_line > > -86.2% -40.0Mi [ = ] 0 .debug_loc > > -42.0% -64.1Mi [ = ] 0 .debug_info > > -22.1% -122Mi [ = ] 0 TOTAL > > > > Hi Nick, > > thanks for the patch. > > I have slightly modified it to adapt to Linux v5.7-rc4 (what was your base?). > > Which linker did you use and has it an impact if you switch from > ld.bfd to ld.lld? > > I tried a first normal run and in a 2nd one with > CONFIG_DEBUG_INFO_COMPRESSED=y both with clang-10 and ld.lld-10. > > My numbers (sizes in MiB): > > [ diffconfig ] > > $ scripts/diffconfig /boot/config-5.7.0-rc4-1-amd64-clang > /boot/config-5.7.0-rc4-2-amd64-clang > BUILD_SALT "5.7.0-rc4-1-amd64-clang" -> "5.7.0-rc4-2-amd64-clang" > +DEBUG_INFO_COMPRESSED y > > [ compiler and linker ] > > $ clang-10 -v > ClangBuiltLinux clang version 10.0.1 > (https://github.com/llvm/llvm-project > 92d5c1be9ee93850c0a8903f05f36a23ee835dc2) > Target: x86_64-unknown-linux-gnu > Thread model: posix > InstalledDir: /home/dileks/src/llvm-toolchain/install/bin > Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10 > Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8 > Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9 > Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10 > Candidate multilib: .;@m64 > Candidate multilib: 32;@m32 > Candidate multilib: x32;@mx32 > Selected multilib: .;@m64 > > $ ld.lld-10 -v > LLD 10.0.1 (https://github.com/llvm/llvm-project > 92d5c1be9ee93850c0a8903f05f36a23ee835dc2) (compatible with GNU > linkers) > > [ sizes vmlinux ] > > $ du -m 5.7.0-rc4-*/vmlinux* > 409 5.7.0-rc4-1-amd64-clang/vmlinux > 7 5.7.0-rc4-1-amd64-clang/vmlinux.compressed > 404 5.7.0-rc4-1-amd64-clang/vmlinux.o > 324 5.7.0-rc4-2-amd64-clang/vmlinux > 7 5.7.0-rc4-2-amd64-clang/vmlinux.compressed > 299 5.7.0-rc4-2-amd64-clang/vmlinux.o > > [ readelf (.debug_info as example) ] > > $ readelf -S vmlinux.o > [33] .debug_info PROGBITS 0000000000000000 01d6a5e8 > 0000000006be1ee6 0000000000000000 0 0 1 > > $ readelf -S vmlinux.o > [33] .debug_info PROGBITS 0000000000000000 01749f18 > 0000000002ef04d2 0000000000000000 C 0 0 1 <--- > XXX: "C (compressed)" Flag > > Key to Flags: > W (write), A (alloc), X (execute), M (merge), S (strings), I (info), > L (link order), O (extra OS processing required), G (group), T (TLS), > C (compressed), x (unknown), o (OS specific), E (exclude), > l (large), p (processor specific) > > [ sizes linux-image debian packages ] > > $ du -m 5.7.0-rc4-*/linux-image*.deb > 47 5.7.0-rc4-1-amd64-clang/linux-image-5.7.0-rc4-1-amd64-clang_5.7.0~rc4-1~bullseye+dileks1_amd64.deb > 424 5.7.0-rc4-1-amd64-clang/linux-image-5.7.0-rc4-1-amd64-clang-dbg_5.7.0~rc4-1~bullseye+dileks1_amd64.deb > 47 5.7.0-rc4-2-amd64-clang/linux-image-5.7.0-rc4-2-amd64-clang_5.7.0~rc4-2~bullseye+dileks1_amd64.deb > 771 5.7.0-rc4-2-amd64-clang/linux-image-5.7.0-rc4-2-amd64-clang-dbg_5.7.0~rc4-2~bullseye+dileks1_amd64.deb > > [ sizes linux-git dir (compilation finished ] > > 5.7.0-rc4-1-amd64-clang: 17963 /home/dileks/src/linux-kernel/linux > 5.7.0-rc4-2-amd64-clang: 14328 /home/dileks/src/linux-kernel/linux > > [ xz compressed linux-image-dbg packages ] > > $ file linux-image-5.7.0-rc4-1-amd64-clang-dbg_5.7.0~rc4-1~bullseye+dileks1_amd64.deb > linux-image-5.7.0-rc4-1-amd64-clang-dbg_5.7.0~rc4-1~bullseye+dileks1_amd64.deb: > Debian binary package (format 2.0), with control.tar.xz, data > compression xz > $ file linux-image-5.7.0-rc4-2-amd64-clang-dbg_5.7.0~rc4-2~bullseye+dileks1_amd64.deb > linux-image-5.7.0-rc4-2-amd64-clang-dbg_5.7.0~rc4-2~bullseye+dileks1_amd64.deb: > Debian binary package (format 2.0), with control.tar.xz, data > compression xz > > [ file-lists ] > > $ dpkg --contents > linux-image-5.7.0-rc4-1-amd64-clang-dbg_5.7.0~rc4-1~bullseye+dileks1_amd64.deb > | wc -l > 4395 > $ dpkg --contents > linux-image-5.7.0-rc4-2-amd64-clang-dbg_5.7.0~rc4-2~bullseye+dileks1_amd64.deb > | wc -l > 4395 > > [ file-lists vmlinux ] > > $ dpkg --contents > linux-image-5.7.0-rc4-1-amd64-clang-dbg_5.7.0~rc4-1~bullseye+dileks1_amd64.deb > | grep vmlinux > -rwxr-xr-x root/root 428588312 2020-05-04 06:15 > ./usr/lib/debug/lib/modules/5.7.0-rc4-1-amd64-clang/vmlinux > lrwxrwxrwx root/root 0 2020-05-04 06:15 > ./usr/lib/debug/boot/vmlinux-5.7.0-rc4-1-amd64-clang -> > ../lib/modules/5.7.0-rc4-1-amd64-clang/vmlinux > lrwxrwxrwx root/root 0 2020-05-04 06:15 > ./usr/lib/debug/vmlinux-5.7.0-rc4-1-amd64-clang -> > lib/modules/5.7.0-rc4-1-amd64-clang/vmlinux > > $ dpkg --contents > linux-image-5.7.0-rc4-2-amd64-clang-dbg_5.7.0~rc4-2~bullseye+dileks1_amd64.deb > | grep vmlinux > -rwxr-xr-x root/root 339341456 2020-05-04 12:24 > ./usr/lib/debug/lib/modules/5.7.0-rc4-2-amd64-clang/vmlinux > lrwxrwxrwx root/root 0 2020-05-04 12:24 > ./usr/lib/debug/boot/vmlinux-5.7.0-rc4-2-amd64-clang -> > ../lib/modules/5.7.0-rc4-2-amd64-clang/vmlinux > lrwxrwxrwx root/root 0 2020-05-04 12:24 > ./usr/lib/debug/vmlinux-5.7.0-rc4-2-amd64-clang -> > lib/modules/5.7.0-rc4-2-amd64-clang/vmlinux > > [ conclusion ] > > As you can see there is a size-reduction in case of vmlinux/vmlinux.o > (debug) files... > ...and my linux-git directory in total is smaller: 17963M vs. 14328M. > > But the resulting linux-image-dbg file is much fatter: 424M vs. 711M. > XZ-compressing the gz/zlib-compressed vmlinux (debug) file results in > a fatter linux-image-dbg package. I also confirmed that, but this would not be a blocker of this patch. Users can disable CONFIG_DEBUG_INFO_COMPRESSED if they care about the debug package size. -- Best Regards Masahiro Yamada
