On Tue, Nov 25, 2025 at 03:41:38PM -0100, Graham Inggs wrote: > Hi Adrian
Hi Graham, > Thanks for digging into this! > > On Mon, 24 Nov 2025 at 03:22, Adrian Bunk <[email protected]> wrote: > > Already 16.1.0-1 did put mold in CXXFLAGS instead of LDFLAGS (using > > LDFLAGS seems to work), and this removed the -O2 resulting in building > > without optimization - which made the build faster. > > So mold does not really speed things up? > Rather, the speed up is due to the accidental removal of the optimization > flags? yes. > > I would have a tendency to revert the mold change and instead do > > optimize=-lto, but whether the latter actually solves the problem > > for Ubuntu is unproven. > > Do you mean reverting to the packaging state of 16.1.0-2? Yes. > If so, I am in favour. The Ubuntu issues can be fixed in Ubuntu. > > What about lowering optimization for riscv64? Or just not building > there until the hardware is able to cope? >... I would rather try to avoid lowering optimization, and -O0 of huge C++ code would strike me as particularly bad. Creating debug info is actually confirmed to be expensive for C++ code, and GCC 15 on riscv64 even is significantly slower on that than GCC 14.[1] For siconos (#1121341) the following brought the compilation of the problematic file from timeout after 12 hours on the buildd down to ~ 2 hours for me: ifneq (,$(filter $(DEB_HOST_ARCH), riscv64)) export DEB_CXXFLAGS_MAINT_APPEND += -g1 endif I would guess that for trilinos this would get the compile time from 11 days back down to ~ 3 days (untested). > Regards > Graham >... cu Adrian [1] https://lists.debian.org/debian-riscv/2025/09/msg00019.html
