On Fri, 2020-07-24 at 22:30 +0200, Igor Raits wrote: > On Fri, 2020-07-24 at 14:27 -0600, Jeff Law wrote: > > On Fri, 2020-07-24 at 22:24 +0200, Igor Raits wrote: > > > On Fri, 2020-07-24 at 13:29 -0600, Jeff Law wrote: > > > > On Fri, 2020-07-24 at 19:12 +0000, Artem Tim wrote: > > > > > Hi. In rare cases building packages with LTO producing binaries > > > > > or > > > > > libraries which have bigger size then if they have built > > > > > without > > > > > LTO. For example 'kitty' package: > > > > > > > > > > * with LTO: > > > > > - koji task > > > > > https://koji.fedoraproject.org/koji/taskinfo?taskID=47762998 > > > > > 1.79 MB glfw-wayland.so > > > > > 1.99 MB glfw-x11.so > > > > > 4.78 MB fast_data_types.so > > > > > 8.56 MB total > > > > > > > > > > * no LTO > > > > > - koji > > > > > https://koji.fedoraproject.org/koji/taskinfo?taskID=47769854 > > > > > 1.65 MB glfw-wayland.so > > > > > 1.84 MB glfw-x11.so > > > > > 4.51 MB fast_data_types.so > > > > > 8.00 MB total > > > > > > > > > > Difference is 7%. What we should do in such case? Should we > > > > > disable > > > > > LTO for such packages? Or there is still could be gains from > > > > > faster > > > > > code execution speed? > > > > I'd tend to leave LTO on, but it's totally your call. Without > > > > looking at the > > > > binaries, sources and compiler dumps I'd hazard a guess you're > > > > getting a lot of > > > > cross module inlining, but very little identical code folding. > > > > THe > > > > former tends > > > > to make things bigger, but faster. The latter tends to shrink > > > > code > > > > with little > > > > impact on runtime performance. > > > > > > From what I see in this case, -ffat-lto-objects generates code that > > > is > > > bigger than without -flto. -flto alone generates smaller code than > > > without -flto. > > The fat-lto-objects bits are not used during an LTO link. They exist > > solely to > > cover the case where there's a .o/.a that ends up installed. > > Well, I tell what I see :) > > Compiling kitty with settings below produces this big > /usr/lib64/kitty/kitty/fast_data_types.so: > > * Without any LTO-related flags: 4.52 MB > * With -flto: 4.30 MB > * With -flto -ffat-lto-objects: 4.79 MB > > Well, I did not run compilation multiple times but don't think it will > change much. That's quite bizarre. I'll put it on the list of things to investigate. jeff _______________________________________________ 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
