| Message ID | 20200526170321.137238-1-ndesaulniers@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v4] Makefile: support compressed debug info | expand |
On Tue, May 26, 2020 at 10:03 AM Nick Desaulniers <ndesaulniers@google.com> 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 > > For x86_64 defconfig + LLVM=1 (before): > Elapsed (wall clock) time (h:mm:ss or m:ss): 3:22.03 > Maximum resident set size (kbytes): 43856 > > For x86_64 defconfig + LLVM=1 (after): > Elapsed (wall clock) time (h:mm:ss or m:ss): 3:32.52 > Maximum resident set size (kbytes): 1566776 > > Thanks to: > Nick Clifton helped us to provide the minimal binutils version. > Sedat Dilet found an increase in size of debug .deb package. > > Cc: Nick Clifton <nickc@redhat.com> > Cc: Sedat Dilek <sedat.dilek@gmail.com> > Suggested-by: David Blaikie <blaikie@google.com> > Reviewed-by: Fangrui Song <maskray@google.com> > Tested-by: Sedat Dilek <sedat.dilek@gmail.com> > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> > --- > Changes V3 -> V4: > * Add thanks line to commit message as per Masahiro. > * Swap Sugguested-by to Cc for two lines in commit message, as per > Masahiro. > > Changes V2 -> V3: > * Fix blaikie@'s email addr. > * Fix Fangrui's Reviewed-by tag as per Masahiro. > * Fix help text as per Masahiro. > * Fix -Wa$(comma)foo as per Masahiro. > > Changes V1 -> V2: > * rebase on linux-next. > * Add assembler flags as per Fangrui. > * Add note about KDEB_COMPRESS+scripts/package/builddeb > as per Sedat and Masahiro. > * Add note about bintutils version requirements as per Nick C. > * Add note about measured increased build time and max RSS. > > Makefile | 6 ++++++ > arch/arm64/kernel/vdso32/Makefile | 2 +- Sorry, I was wondering why Will and TGLX got cc'ed. My tree was dirty when I amended ... was carrying another patch to send, please disregard v4, and sorry for the noise. > lib/Kconfig.debug | 17 +++++++++++++++++ > 3 files changed, 24 insertions(+), 1 deletion(-) > > diff --git a/Makefile b/Makefile > index 71687bfe1cd9..be8835296754 100644 > --- a/Makefile > +++ b/Makefile > @@ -822,6 +822,12 @@ DEBUG_CFLAGS += $(call cc-option, -femit-struct-debug-baseonly) \ > $(call cc-option,-fno-var-tracking) > endif > > +ifdef CONFIG_DEBUG_INFO_COMPRESSED > +DEBUG_CFLAGS += -gz=zlib > +KBUILD_AFLAGS += -Wa,--compress-debug-sections=zlib > +KBUILD_LDFLAGS += --compress-debug-sections=zlib > +endif > + > KBUILD_CFLAGS += $(DEBUG_CFLAGS) > export DEBUG_CFLAGS > > diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile > index 3964738ebbde..5fd7792d03fc 100644 > --- a/arch/arm64/kernel/vdso32/Makefile > +++ b/arch/arm64/kernel/vdso32/Makefile > @@ -135,7 +135,7 @@ c-obj-vdso-gettimeofday := vgettimeofday.o > asm-obj-vdso := sigreturn.o > > ifneq ($(c-gettimeofday-y),) > -VDSO_CFLAGS_gettimeofday_o += -include $(c-gettimeofday-y) > +VDSO_CFLAGS_gettimeofday_o += -include $(c-gettimeofday-y) -marm > endif > > VDSO_CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index b8f023e054b9..7fc82dcf814b 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -225,6 +225,23 @@ config DEBUG_INFO_REDUCED > DEBUG_INFO build and compile times are reduced too. > Only works with newer gcc versions. > > +config DEBUG_INFO_COMPRESSED > + bool "Compressed debugging information" > + depends on DEBUG_INFO > + depends on $(cc-option,-gz=zlib) > + depends on $(as-option,-Wa$(comma)--compress-debug-sections=zlib) > + depends on $(ld-option,--compress-debug-sections=zlib) > + help > + Compress the debug information using zlib. Requires GCC 5.0+ or Clang > + 5.0+, binutils 2.26+, and zlib. > + > + Users of dpkg-deb via scripts/package/builddeb may find an increase in > + size of their debug .deb packages with this config set, due to the > + debug info being compressed with zlib, then the object files being > + recompressed with a different compression scheme. But this is still > + preferable to setting $KDEB_COMPRESS to "none" which would be even > + larger. > + > config DEBUG_INFO_SPLIT > bool "Produce split debuginfo in .dwo files" > depends on DEBUG_INFO > -- > 2.27.0.rc0.183.gde8f92d652-goog >
diff --git a/Makefile b/Makefile index 71687bfe1cd9..be8835296754 100644 --- a/Makefile +++ b/Makefile @@ -822,6 +822,12 @@ DEBUG_CFLAGS += $(call cc-option, -femit-struct-debug-baseonly) \ $(call cc-option,-fno-var-tracking) endif +ifdef CONFIG_DEBUG_INFO_COMPRESSED +DEBUG_CFLAGS += -gz=zlib +KBUILD_AFLAGS += -Wa,--compress-debug-sections=zlib +KBUILD_LDFLAGS += --compress-debug-sections=zlib +endif + KBUILD_CFLAGS += $(DEBUG_CFLAGS) export DEBUG_CFLAGS diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile index 3964738ebbde..5fd7792d03fc 100644 --- a/arch/arm64/kernel/vdso32/Makefile +++ b/arch/arm64/kernel/vdso32/Makefile @@ -135,7 +135,7 @@ c-obj-vdso-gettimeofday := vgettimeofday.o asm-obj-vdso := sigreturn.o ifneq ($(c-gettimeofday-y),) -VDSO_CFLAGS_gettimeofday_o += -include $(c-gettimeofday-y) +VDSO_CFLAGS_gettimeofday_o += -include $(c-gettimeofday-y) -marm endif VDSO_CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index b8f023e054b9..7fc82dcf814b 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -225,6 +225,23 @@ config DEBUG_INFO_REDUCED DEBUG_INFO build and compile times are reduced too. Only works with newer gcc versions. +config DEBUG_INFO_COMPRESSED + bool "Compressed debugging information" + depends on DEBUG_INFO + depends on $(cc-option,-gz=zlib) + depends on $(as-option,-Wa$(comma)--compress-debug-sections=zlib) + depends on $(ld-option,--compress-debug-sections=zlib) + help + Compress the debug information using zlib. Requires GCC 5.0+ or Clang + 5.0+, binutils 2.26+, and zlib. + + Users of dpkg-deb via scripts/package/builddeb may find an increase in + size of their debug .deb packages with this config set, due to the + debug info being compressed with zlib, then the object files being + recompressed with a different compression scheme. But this is still + preferable to setting $KDEB_COMPRESS to "none" which would be even + larger. + config DEBUG_INFO_SPLIT bool "Produce split debuginfo in .dwo files" depends on DEBUG_INFO
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 For x86_64 defconfig + LLVM=1 (before): Elapsed (wall clock) time (h:mm:ss or m:ss): 3:22.03 Maximum resident set size (kbytes): 43856 For x86_64 defconfig + LLVM=1 (after): Elapsed (wall clock) time (h:mm:ss or m:ss): 3:32.52 Maximum resident set size (kbytes): 1566776 Thanks to: Nick Clifton helped us to provide the minimal binutils version. Sedat Dilet found an increase in size of debug .deb package. Cc: Nick Clifton <nickc@redhat.com> Cc: Sedat Dilek <sedat.dilek@gmail.com> Suggested-by: David Blaikie <blaikie@google.com> Reviewed-by: Fangrui Song <maskray@google.com> Tested-by: Sedat Dilek <sedat.dilek@gmail.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> --- Changes V3 -> V4: * Add thanks line to commit message as per Masahiro. * Swap Sugguested-by to Cc for two lines in commit message, as per Masahiro. Changes V2 -> V3: * Fix blaikie@'s email addr. * Fix Fangrui's Reviewed-by tag as per Masahiro. * Fix help text as per Masahiro. * Fix -Wa$(comma)foo as per Masahiro. Changes V1 -> V2: * rebase on linux-next. * Add assembler flags as per Fangrui. * Add note about KDEB_COMPRESS+scripts/package/builddeb as per Sedat and Masahiro. * Add note about bintutils version requirements as per Nick C. * Add note about measured increased build time and max RSS. Makefile | 6 ++++++ arch/arm64/kernel/vdso32/Makefile | 2 +- lib/Kconfig.debug | 17 +++++++++++++++++ 3 files changed, 24 insertions(+), 1 deletion(-)