Date: Sat, 6 Dec 2025 19:24:33 +0200 From: Konstantin Belousov <kib@freebsd.org> To: Mateusz Guzik <mjguzik@gmail.com> Cc: FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: performance regressions in 15.0 Message-ID: <aTRm0WW7xaKsOKx1@kib.kiev.ua> In-Reply-To: <CAGudoHFUJ23yUWPq7_VS2ek0zoGQOS42HB00n-hWspA3Cb4-XQ@mail.gmail.com>
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On Sat, Dec 06, 2025 at 11:50:08AM +0100, Mateusz Guzik wrote: > II. compilation speed > > The the real and serious problem. Both versions of the system ship the > same clang version: > FreeBSD clang version 19.1.7 (https://github.com/llvm/llvm-project.git > llvmorg-19.1.7-0-gcd708029e0b2) > Target: x86_64-unknown-freebsd14.3 > Thread model: posix > InstalledDir: /usr/bin > > FreeBSD clang version 19.1.7 (https://github.com/llvm/llvm-project.git > llvmorg-19.1.7-0-gcd708029e0b2) > Target: x86_64-unknown-freebsd15.0 > Thread model: posix > InstalledDir: /usr/bin > > I found that compiling the will-it-scale suite about doubles in real > time needed, along with doubling time spent in userspace. > > will-it-scale needs a little bit of massaging to work, diff at the end. > > check this out (repeabale): while true; do gmake -s clean && time > gmake -s -j 8; done > > 14.3: > gmake -s -j 8 8.93s user 2.03s system 769% cpu 1.42s (1.424) total > gmake -s -j 8 9.02s user 2.16s system 757% cpu 1.48s (1.475) total > gmake -s -j 8 9.29s user 1.95s system 774% cpu 1.45s (1.450) total > gmake -s -j 8 8.97s user 2.46s system 770% cpu 1.48s (1.484) total > gmake -s -j 8 9.13s user 2.30s system 773% cpu 1.48s (1.477) total 14.3 clang/lld are probably statically linked, but I am not sure. Can you confirm this? > > 15.0: > gmake -s -j 8 19.90s user 3.02s system 773% cpu 2.96s (2.963) total > gmake -s -j 8 19.90s user 3.18s system 774% cpu 2.98s (2.979) total > gmake -s -j 8 20.24s user 2.90s system 770% cpu 3.00s (3.005) total > gmake -s -j 8 19.92s user 3.25s system 771% cpu 3.00s (3.003) total > gmake -s -j 8 20.25s user 2.95s system 772% cpu 3.01s (3.006) total But 15.0 is definitely dynamically linked. clang is enormous C++ binary with enormous amount of relocs: $ ldd /usr/bin/cc /usr/bin/cc: libprivateclang.so.19 => /usr/lib/libprivateclang.so.19 (0x27417e200000) libprivatellvm.so.19 => /usr/lib/libprivatellvm.so.19 (0x274183e00000) $ objdump -R /usr/lib/libprivateclang.so.19 | wc -l 232977 $ objdump -R /usr/lib/libprivatellvm.so.19 | wc -l 140712 > > user time *skyrocketed*help
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