On Wed, May 13, 2020 at 4:52 AM Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote: > > Nick, > > On Wed, May 13, 2020 at 4:23 AM Nick Desaulniers > <ndesaulniers@xxxxxxxxxx> wrote: > > > > On Mon, May 11, 2020 at 10:54 PM Masahiro Yamada <masahiroy@xxxxxxxxxx> 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. > > > > >> > > > Nick, > > > > > > I am OK with this patch. > > > > > > Fangrui provided the minimal requirement for > > > --compress-debug-sections=zlib > > > > > > > > > Is it worth recording in the help text? > > > Do you want to send v2? > > > > Yes I'd like to record that information. I can also record Sedat's > > Tested-by tag. Thank you for testing Sedat. > > > > I don't know what "linux-image-dbg file" are, or why they would be > > bigger. The size of the debug info is the primary concern with this > > config. It sounds like however that file is created might be > > problematic. > > > > As Sedat explained, deb package data > is compressed by xz, which is default. > > You can use another compression method, > or disable compression if you desire. > > > > "man dpkg-deb" says as follows: > > -Zcompress-type > Specify which compression type to use when building a package. > Allowed values are gzip, xz (since dpkg 1.15.6), and none > (default is xz). > > > > Kbuild supports KDEB_COMPRESS variable > to change the compression method. > See line 46 of scripts/package/builddeb. > Hi Masahiro, thanks for the clarification and the informations. With next RC I will add KDEB_COMPRESS=gzip to my build-script and report. Regards, - Sedat - > > If you are interested, > try "make bindeb-pkg" with/without CONFIG_DEBUG_INFO_COMPRESSED, > and compare the size of the generated debug package. > > > > > As Sedat stated, > > (plain data) -> compress by gzip -> compress by xz > > is often less efficient than > > (plain data) -> compress by xz > > > > I hope this is clearer. > > > > > > > > > > Fangrui, I wasn't able to easily find what version of binutils first > > added support. Can you please teach me how to fish? > > > > Another question I had for Fangrui is, if the linker can compress > > these sections, shouldn't we just have the linker do it, not the the > > compiler and assembler? IIUC the debug info can contain relocations, > > so the linker would have to decompress these, perform relocations, > > then recompress these? I guess having the compiler and assembler > > compress the debug info as well would minimize the size of the .o > > files on disk. > > > > Otherwise I should add this flag to the assembler invocation, too, in > > v2. Thoughts? > > > > I have a patch series that enables dwarf5 support in the kernel that > > I'm working up to. I wanted to send this first. Both roughly reduce > > the debug info size by 20% each, though I haven't measured them > > together, yet. Requires ToT binutils because there have been many > > fixes from reports of mine recently. > > -- > > Thanks, > > ~Nick Desaulniers > > > > -- > Best Regards > Masahiro Yamada
