* Zbigniew Jędrzejewski-Szmek:
I think that this really needs to be benchmarked. Without that the
discussion will just go on in circles. There are two nice options for
this: either copr, where you first build the redhat-rpm-config with the
adjusted options and then rebuild some subset of rawhide to be able
to do benchmarks, or just the same thing locally on a server with a bunch
of CPUs. One architecture should be enough.
If that one architecture is x86_64. Note that x86_64 needs
-mno-omit-leaf-frame-pointer, not just -fno-omit-frame-pointer.
i686 will have additional build failures and very different performance
characteristics. ppc64le already uses a backchain, s390x has a
different backchain convention (and may not be affected by
-fno-omit-frame-pointer). aarch64 needs -mno-omit-leaf-frame-pointer as
well.
Mini-rebuilds like that take a few days, so it's entirely
possible to
do.
I pushed a change to rawhide glibc which makes it inherit the
-fno-omit-frame-pointer and -mno-omit-leaf-frame-pointer from
redhat-rpm-config. I think both flags are required if you want to use
the frame pointers for accurate unwinding.
GCC (for libgcc and libstdc++) will need very different changes. I
don't think it inherits the build flags, either.
Thanks,
Florian