Jan Kratochvil wrote on Thu, Sep 24, 2020: > > That talk doesn't load for me, sorry if I ask something answered in > > there. > > I have added a title there now but the URL loads for me even in lynx+wget. Yeah sorry it finally loaded after 10+ minutes, that was weird. > Copy-pasted it at the bottom of this mail. I do not know the talk but TL;DR > existing DWARF contains some dead DIEs - unused/deduplicated functions and also > -fdebug-types-section declarations/skeletons which can be removed or converted > to direct DIE references respectively. That way one could reduce the size like > DWZ does but without needing any new complicated support in DWARF consumers. Ok, avoiding duplicate data makes sense there is quite a lot in there. > That is orthogonal - that is one can add it to DWZ or -fdebug-types-section > the same way. It would be for another Fedora Change proposal but I do not > think it matters for F-33 as it already implements: > https://fedoraproject.org/wiki/Changes/BtrfsByDefault#Compression Good point. I did think of rpm size (double compression doesn't work well and rpms use better compression than zlib) but not filesystem compression. Everyone won't benefit from that right away but I guess it makes sense. > I haven't yet checked whether that applies to /usr/lib/debug/ by default. > btrfs is using zstd which has better performance than zlib. I was considering > adding an ELF section compression extension for zstd but with btrfs > transparent compression that looks as not useful. I don't have very much there but it does work well: # compsize /usr/lib/debug/ Processed 720 files, 2232 regular extents (2239 refs), 1 inline. Type Perc Disk Usage Uncompressed Referenced TOTAL 32% 74M 229M 230M none 100% 644K 644K 644K zstd 32% 73M 229M 229M > That 3.3% size reduction=advantage of DWZ against -fdebug-types-section is > calculated for *-debuginfo.rpm (3.3% is for the whole distribution incl. > binaries, for debug/ itself it is 6.35%). Also it is calculated for DWARF-4, > F-34 will hopefully switch to DWARF-5 (which is smaller by 10-20%) but DWZ is > not yet ported to DWARF-5 so it is impossible to compare -fdebug-types-section > vs. DWZ size for DWARF-5. Ok. That definitely makes more sense to me, thanks for clarifying this. -- Dominique _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx
