On Wed, 30 Sep 2020 01:31:29 +0200, Jeff Law wrote: > But the GCC community > doesn't really test that option and it's known to be broken with LTO.
I haven't seen any GCC PR for -fdebug-types-section being broken with LTO. During one abigail diff I did not see any difference. I plan to run a full distribution abigail massrebuild+check as stated in the Change to exclude any possible incompatibilities. That would discover unfiled GCC problems with -fdebug-types-section. Also I do not see why fixing -fdebug-types-section should be anyhow difficult if the compiler can produce -fno-debug-types-section. I can also write postprocessor to get -fdebug-types-section if GCC is unable to do that. That would sure lose the -fdebug-types-section compilation time performance benefits. > And, not surprisingly, our team has had significant input on the options > we're using *and* the GCC implementation of those options. We make > recommendations based on our experiences. That same experience would lead us > to recommending against -fdebug-types-section at this time. I think I have also some DWARF experience. Could you suggest what is wrong on -fdebug-types-section? > It would certainly be good to improve the on-disk distro size. OK, going to file a Change to enable gcc -gz option (zlib section compression) as that will reduce on-disk *.debug size by 52.84%! Then we can disable both DWZ and -fdebug-types-section as those become pointless then. > So the only paths forward I see are to either fix -fdebug-types-section or > improve dwz. And obviously much easier is to fix -fdebug-types-section than DWZ (if there are really any bugs in -fdebug-types-section, there are known bugs nobody wants to fix in DWZ). > Putting my Red Hat hat on, I get pushback from PM on *any* size increases in > the RHEL space. When we start talking about RHEL (and CentOS) DWZ is completely pointless then as DWZ there saves only 0.28% of *-debuginfo.rpm (20MB of 7.2GB). Therefore approx. 0.14% of the distribution size. > As much as we'd like to be in a world were a 1% increase in distro > size doesn't matter, that's not the actual world we live in. Unfortunately DWZ cannot decrease RHEL size by that 1%. > And our RHEL customers absolutey do care about the size of debuginfo > becuause it affects link times. System debuginfo format does not affect link times. Using DWZ during linking customer's applications definitely only increases linking time as it is an extra step. Not sure what do you talk about. Production of debuginfo does affect compilation time but that is unrelated to DWZ. Production of debug info affects linking time only if -gsplit-dwarf is not used. (-gsplit-dwarf still affects linking time but only very little.) But that is all unrelated to DWZ. Jan _______________________________________________ devel mailing list -- devel@lists.fedoraproject.org To unsubscribe send an email to devel-le...@lists.fedoraproject.org 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@lists.fedoraproject.org
