Hi Yinan, Yinan Liu <yinan@xxxxxxxxxxxxxxxxx> writes: > When the kernel starts, the initialization of ftrace takes > up a portion of the time (approximately 6~8ms) to sort mcount > addresses. We can save this time by moving mcount-sorting to > compile time. > > Signed-off-by: Yinan Liu <yinan@xxxxxxxxxxxxxxxxx> > Reported-by: kernel test robot <lkp@xxxxxxxxx> > Reported-by: kernel test robot <oliver.sang@xxxxxxxxx> > --- > kernel/trace/ftrace.c | 11 +++- > scripts/Makefile | 6 +- > scripts/link-vmlinux.sh | 6 +- > scripts/sorttable.c | 2 + > scripts/sorttable.h | 120 +++++++++++++++++++++++++++++++++++++++- > 5 files changed, 137 insertions(+), 8 deletions(-) while i like the idea, this unfortunately breaks ftrace on s390. The reason for that is that the compiler generates relocation entries for all the addresses in __mcount_loc. During boot, the s390 decompressor iterates through all the relocations and overwrites the nicely sorted list between __start_mcount_loc and __stop_mcount_loc with the unsorted list because the relocations entries are not adjusted. Of course we could just disable that option, but that would make us different compared to x86 which i don't like. Adding code to sort the relocation would of course also fix that, but i don't think it is a good idea to rely on the order of relocations. Any thoughts how a fix could look like, and whether that could also be a problem on other architectures? Thanks Sven
